Merge remote-tracking branch 'origin/master' into new_balancer

Conflicts:
	server/src/main/java/com/metamx/druid/master/DruidMaster.java

client/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>

client/src/main/java/com/metamx/druid/client/CachingClusteredClient.java

@@ -139,18 +139,24 @@ public class CachingClusteredClient<T> implements QueryRunner<T>
     // build set of segments to query
     Set<Pair<ServerSelector, SegmentDescriptor>> segments = Sets.newLinkedHashSet();
 
+    List<TimelineObjectHolder<String, ServerSelector>> serversLookup = Lists.newLinkedList();
+
     for (Interval interval : rewrittenQuery.getIntervals()) {
-      List<TimelineObjectHolder<String, ServerSelector>> serversLookup = timeline.lookup(interval);
+      serversLookup.addAll(timeline.lookup(interval));
+    }
 
-      for (TimelineObjectHolder<String, ServerSelector> holder : serversLookup) {
-        for (PartitionChunk<ServerSelector> chunk : holder.getObject()) {
-          ServerSelector selector = chunk.getObject();
-          final SegmentDescriptor descriptor = new SegmentDescriptor(
-              holder.getInterval(), holder.getVersion(), chunk.getChunkNumber()
-          );
+    // Let tool chest filter out unneeded segments
+    final List<TimelineObjectHolder<String, ServerSelector>> filteredServersLookup =
+        toolChest.filterSegments(query, serversLookup);
 
-          segments.add(Pair.of(selector, descriptor));
-        }
+    for (TimelineObjectHolder<String, ServerSelector> holder : filteredServersLookup) {
+      for (PartitionChunk<ServerSelector> chunk : holder.getObject()) {
+        ServerSelector selector = chunk.getObject();
+        final SegmentDescriptor descriptor = new SegmentDescriptor(
+            holder.getInterval(), holder.getVersion(), chunk.getChunkNumber()
+        );
+
+        segments.add(Pair.of(selector, descriptor));
       }
     }
 

client/src/main/java/com/metamx/druid/client/ServerInventoryManager.java

@@ -19,7 +19,6 @@
 
 package com.metamx.druid.client;
 
-import com.google.common.collect.Maps;
 import com.metamx.common.Pair;
 import com.metamx.common.logger.Logger;
 import com.metamx.phonebook.PhoneBook;
@@ -27,12 +26,13 @@ import com.metamx.phonebook.PhoneBookPeon;
 
 import java.util.Iterator;
 import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 
 /**
  */
 public class ServerInventoryManager extends InventoryManager<DruidServer>
 {
-  private static final Map<String, Integer> removedSegments = Maps.newHashMap();
+  private static final Map<String, Integer> removedSegments = new ConcurrentHashMap<String, Integer>();
 
   public ServerInventoryManager(
       ServerInventoryManagerConfig config,

client/src/main/java/com/metamx/druid/initialization/Initialization.java

@@ -23,7 +23,6 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Throwables;
 import com.google.common.io.Closeables;
 import com.google.common.util.concurrent.ThreadFactoryBuilder;
-import com.metamx.common.ISE;
 import com.metamx.common.concurrent.ScheduledExecutorFactory;
 import com.metamx.common.lifecycle.Lifecycle;
 import com.metamx.common.logger.Logger;
@@ -31,8 +30,8 @@ import com.metamx.druid.client.ZKPhoneBook;
 import com.metamx.druid.http.FileRequestLogger;
 import com.metamx.druid.http.RequestLogger;
 import com.metamx.druid.utils.PropUtils;
-import com.metamx.druid.zk.StringZkSerializer;
 import com.metamx.druid.zk.PropertiesZkSerializer;
+import com.metamx.druid.zk.StringZkSerializer;
 import com.netflix.curator.framework.CuratorFramework;
 import com.netflix.curator.framework.CuratorFrameworkFactory;
 import com.netflix.curator.retry.ExponentialBackoffRetry;
@@ -42,7 +41,6 @@ import com.netflix.curator.x.discovery.ServiceInstance;
 import com.netflix.curator.x.discovery.ServiceProvider;
 import org.I0Itec.zkclient.ZkClient;
 import org.I0Itec.zkclient.ZkConnection;
-
 import org.mortbay.jetty.Connector;
 import org.mortbay.jetty.Server;
 import org.mortbay.jetty.nio.SelectChannelConnector;
@@ -53,7 +51,6 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.util.Properties;
 import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
 
 /**
  */

client/src/main/java/com/metamx/druid/merge/ClientKillQuery.java

@@ -0,0 +1,41 @@
+package com.metamx.druid.merge;
+
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import org.joda.time.Interval;
+
+/**
+ */
+public class ClientKillQuery
+{
+  private final String dataSource;
+  private final Interval interval;
+
+  @JsonCreator
+  public ClientKillQuery(
+      @JsonProperty("dataSource") String dataSource,
+      @JsonProperty("interval") Interval interval
+  )
+  {
+    this.dataSource = dataSource;
+    this.interval = interval;
+  }
+
+  @JsonProperty
+  public String getType()
+  {
+    return "kill";
+  }
+
+  @JsonProperty
+  public String getDataSource()
+  {
+    return dataSource;
+  }
+
+  @JsonProperty
+  public Interval getInterval()
+  {
+    return interval;
+  }
+}

client/src/main/java/com/metamx/druid/query/QueryToolChest.java

@@ -22,18 +22,19 @@ package com.metamx.druid.query;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.google.common.base.Function;
 import com.metamx.common.guava.Sequence;
+import com.metamx.druid.LogicalSegment;
 import com.metamx.druid.Query;
 import com.metamx.emitter.service.ServiceMetricEvent;
-
+import java.util.List;
 
 /**
  * The broker-side (also used by server in some cases) API for a specific Query type.  This API is still undergoing
  * evolution and is only semi-stable, so proprietary Query implementations should be ready for the potential
  * maintenance burden when upgrading versions.
  */
-public interface QueryToolChest<ResultType, QueryType extends Query<ResultType>>
+public abstract class QueryToolChest<ResultType, QueryType extends Query<ResultType>>
 {
-  public QueryRunner<ResultType> mergeResults(QueryRunner<ResultType> runner);
+  public abstract QueryRunner<ResultType> mergeResults(QueryRunner<ResultType> runner);
 
   /**
    * This method doesn't belong here, but it's here for now just to make it work.
@@ -41,11 +42,24 @@ public interface QueryToolChest<ResultType, QueryType extends Query<ResultType>>
    * @param seqOfSequences
    * @return
    */
-  public Sequence<ResultType> mergeSequences(Sequence<Sequence<ResultType>> seqOfSequences);
-  public ServiceMetricEvent.Builder makeMetricBuilder(QueryType query);
-  public Function<ResultType, ResultType> makeMetricManipulatorFn(QueryType query, MetricManipulationFn fn);
-  public TypeReference<ResultType> getResultTypeReference();
-  public <T> CacheStrategy<ResultType, T, QueryType> getCacheStrategy(QueryType query);
-  public QueryRunner<ResultType> preMergeQueryDecoration(QueryRunner<ResultType> runner);
-  public QueryRunner<ResultType> postMergeQueryDecoration(QueryRunner<ResultType> runner);
+  public abstract Sequence<ResultType> mergeSequences(Sequence<Sequence<ResultType>> seqOfSequences);
+  public abstract ServiceMetricEvent.Builder makeMetricBuilder(QueryType query);
+  public abstract Function<ResultType, ResultType> makeMetricManipulatorFn(QueryType query, MetricManipulationFn fn);
+  public abstract TypeReference<ResultType> getResultTypeReference();
+
+  public <T> CacheStrategy<ResultType, T, QueryType> getCacheStrategy(QueryType query) {
+    return null;
+  }
+
+  public QueryRunner<ResultType> preMergeQueryDecoration(QueryRunner<ResultType> runner) {
+    return runner;
+  }
+
+  public QueryRunner<ResultType> postMergeQueryDecoration(QueryRunner<ResultType> runner) {
+    return runner;
+  }
+
+  public <T extends LogicalSegment> List<T> filterSegments(QueryType query, List<T> segments) {
+    return segments;
+  }
 }

client/src/main/java/com/metamx/druid/query/group/GroupByQueryQueryToolChest.java

@@ -54,7 +54,7 @@ import java.util.Properties;
 
 /**
  */
-public class GroupByQueryQueryToolChest implements QueryToolChest<Row, GroupByQuery>
+public class GroupByQueryQueryToolChest extends QueryToolChest<Row, GroupByQuery>
 {
 
   private static final TypeReference<Row> TYPE_REFERENCE = new TypeReference<Row>(){};
@@ -177,22 +177,4 @@ public class GroupByQueryQueryToolChest implements QueryToolChest<Row, GroupByQu
   {
     return TYPE_REFERENCE;
   }
-
-  @Override
-  public CacheStrategy<Row, Object, GroupByQuery> getCacheStrategy(GroupByQuery query)
-  {
-    return null;
-  }
-
-  @Override
-  public QueryRunner<Row> preMergeQueryDecoration(QueryRunner<Row> runner)
-  {
-    return runner;
-  }
-
-  @Override
-  public QueryRunner<Row> postMergeQueryDecoration(QueryRunner<Row> runner)
-  {
-    return runner;
-  }
 }

client/src/main/java/com/metamx/druid/query/metadata/SegmentMetadataQueryQueryToolChest.java

@@ -51,7 +51,7 @@ import java.util.Map;
 import java.util.Set;
 
 
-public class SegmentMetadataQueryQueryToolChest implements QueryToolChest<SegmentAnalysis, SegmentMetadataQuery>
+public class SegmentMetadataQueryQueryToolChest extends QueryToolChest<SegmentAnalysis, SegmentMetadataQuery>
 {
   private static final TypeReference<SegmentAnalysis> TYPE_REFERENCE = new TypeReference<SegmentAnalysis>(){};
   private static final byte[] SEGMENT_METADATA_CACHE_PREFIX = new byte[]{0x4};
@@ -220,18 +220,6 @@ public class SegmentMetadataQueryQueryToolChest implements QueryToolChest<Segmen
     };
   }
 
-  @Override
-  public QueryRunner<SegmentAnalysis> preMergeQueryDecoration(QueryRunner<SegmentAnalysis> runner)
-  {
-    return runner;
-  }
-
-  @Override
-  public QueryRunner<SegmentAnalysis> postMergeQueryDecoration(QueryRunner<SegmentAnalysis> runner)
-  {
-    return runner;
-  }
-
   private Ordering<SegmentAnalysis> getOrdering()
   {
     return new Ordering<SegmentAnalysis>()

client/src/main/java/com/metamx/druid/query/search/FragmentSearchQuerySpec.java

@@ -75,7 +75,7 @@ public class FragmentSearchQuerySpec implements SearchQuerySpec
   public boolean accept(String dimVal)
   {
     for (String value : values) {
-      if (!dimVal.toLowerCase().contains(value)) {
+      if (dimVal == null || !dimVal.toLowerCase().contains(value)) {
         return false;
       }
     }

client/src/main/java/com/metamx/druid/query/search/InsensitiveContainsSearchQuerySpec.java

@@ -62,6 +62,9 @@ public class InsensitiveContainsSearchQuerySpec implements SearchQuerySpec
   @Override
   public boolean accept(String dimVal)
   {
+    if (dimVal == null) {
+      return false;
+    }
     return dimVal.toLowerCase().contains(value);
   }
 
@@ -80,8 +83,8 @@ public class InsensitiveContainsSearchQuerySpec implements SearchQuerySpec
   public String toString()
   {
     return "InsensitiveContainsSearchQuerySpec{" +
-             "value=" + value +
-             ", sortSpec=" + sortSpec +
+           "value=" + value +
+           ", sortSpec=" + sortSpec +
            "}";
   }
 }

client/src/main/java/com/metamx/druid/query/search/SearchQueryQueryToolChest.java

@@ -65,7 +65,7 @@ import java.util.Set;
 
 /**
  */
-public class SearchQueryQueryToolChest implements QueryToolChest<Result<SearchResultValue>, SearchQuery>
+public class SearchQueryQueryToolChest extends QueryToolChest<Result<SearchResultValue>, SearchQuery>
 {
   private static final byte SEARCH_QUERY = 0x2;
 
@@ -263,12 +263,6 @@ public class SearchQueryQueryToolChest implements QueryToolChest<Result<SearchRe
     );
   }
 
-  @Override
-  public QueryRunner<Result<SearchResultValue>> postMergeQueryDecoration(final QueryRunner<Result<SearchResultValue>> runner)
-  {
-    return runner;
-  }
-
   private static class SearchThresholdAdjustingQueryRunner implements QueryRunner<Result<SearchResultValue>>
   {
     private final QueryRunner<Result<SearchResultValue>> runner;

client/src/main/java/com/metamx/druid/query/timeboundary/TimeBoundaryQueryQueryToolChest.java

@@ -27,6 +27,7 @@ import com.google.common.collect.Ordering;
 import com.metamx.common.guava.MergeSequence;
 import com.metamx.common.guava.Sequence;
 import com.metamx.common.guava.Sequences;
+import com.metamx.druid.LogicalSegment;
 import com.metamx.druid.Query;
 import com.metamx.druid.collect.OrderedMergeSequence;
 import com.metamx.druid.query.BySegmentSkippingQueryRunner;
@@ -37,7 +38,6 @@ import com.metamx.druid.query.QueryToolChest;
 import com.metamx.druid.result.Result;
 import com.metamx.druid.result.TimeBoundaryResultValue;
 import com.metamx.emitter.service.ServiceMetricEvent;
-
 import org.joda.time.DateTime;
 
 import javax.annotation.Nullable;
@@ -47,7 +47,7 @@ import java.util.List;
 /**
  */
 public class TimeBoundaryQueryQueryToolChest
-    implements QueryToolChest<Result<TimeBoundaryResultValue>, TimeBoundaryQuery>
+    extends QueryToolChest<Result<TimeBoundaryResultValue>, TimeBoundaryQuery>
 {
   private static final byte TIMEBOUNDARY_QUERY = 0x3;
 
@@ -58,6 +58,16 @@ public class TimeBoundaryQueryQueryToolChest
   {
   };
 
+  @Override
+  public <T extends LogicalSegment> List<T> filterSegments(TimeBoundaryQuery query, List<T> input)
+  {
+    if(input.size() <= 1) {
+      return input;
+    }
+
+    return Lists.newArrayList(input.get(0), input.get(input.size() - 1));
+  }
+
   @Override
   public QueryRunner<Result<TimeBoundaryResultValue>> mergeResults(
       final QueryRunner<Result<TimeBoundaryResultValue>> runner
@@ -169,18 +179,6 @@ public class TimeBoundaryQueryQueryToolChest
     };
   }
 
-  @Override
-  public QueryRunner<Result<TimeBoundaryResultValue>> preMergeQueryDecoration(QueryRunner<Result<TimeBoundaryResultValue>> runner)
-  {
-    return runner;
-  }
-
-  @Override
-  public QueryRunner<Result<TimeBoundaryResultValue>> postMergeQueryDecoration(QueryRunner<Result<TimeBoundaryResultValue>> runner)
-  {
-    return runner;
-  }
-
   public Ordering<Result<TimeBoundaryResultValue>> getOrdering()
   {
     return Ordering.natural();

client/src/main/java/com/metamx/druid/query/timeseries/TimeseriesQueryQueryToolChest.java

@@ -61,7 +61,7 @@ import java.util.Map;
 
 /**
  */
-public class TimeseriesQueryQueryToolChest implements QueryToolChest<Result<TimeseriesResultValue>, TimeseriesQuery>
+public class TimeseriesQueryQueryToolChest extends QueryToolChest<Result<TimeseriesResultValue>, TimeseriesQuery>
 {
   private static final byte TIMESERIES_QUERY = 0x0;
 
@@ -259,12 +259,6 @@ public class TimeseriesQueryQueryToolChest implements QueryToolChest<Result<Time
     return new IntervalChunkingQueryRunner<Result<TimeseriesResultValue>>(runner, Period.months(1));
   }
 
-  @Override
-  public QueryRunner<Result<TimeseriesResultValue>> postMergeQueryDecoration(QueryRunner<Result<TimeseriesResultValue>> runner)
-  {
-    return runner;
-  }
-
   public Ordering<Result<TimeseriesResultValue>> getOrdering()
   {
     return Ordering.natural();

common/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>
@@ -80,8 +80,12 @@
             <artifactId>jackson-databind</artifactId>
         </dependency>
         <dependency>
-            <groupId>com.fasterxml.jackson.datatype</groupId>
-            <artifactId>jackson-datatype-joda</artifactId>
+          <groupId>com.fasterxml.jackson.datatype</groupId>
+          <artifactId>jackson-datatype-guava</artifactId>
+        </dependency>
+        <dependency>
+          <groupId>com.fasterxml.jackson.datatype</groupId>
+          <artifactId>jackson-datatype-joda</artifactId>
         </dependency>
         <dependency>
             <groupId>org.jdbi</groupId>

common/src/main/java/com/metamx/druid/LogicalSegment.java

@@ -0,0 +1,8 @@
+package com.metamx.druid;
+
+import org.joda.time.Interval;
+
+public interface LogicalSegment
+{
+  public Interval getInterval();
+}

common/src/main/java/com/metamx/druid/TimelineObjectHolder.java

@@ -24,7 +24,7 @@ import org.joda.time.Interval;
 
 /**
 */
-public class TimelineObjectHolder<VersionType, ObjectType>
+public class TimelineObjectHolder<VersionType, ObjectType> implements LogicalSegment
 {
   private final Interval interval;
   private final VersionType version;
@@ -41,6 +41,7 @@ public class TimelineObjectHolder<VersionType, ObjectType>
     this.object = object;
   }
 
+  @Override
   public Interval getInterval()
   {
     return interval;

common/src/main/java/com/metamx/druid/jackson/DefaultObjectMapper.java

@@ -36,6 +36,7 @@ import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.SerializerProvider;
 import com.fasterxml.jackson.databind.module.SimpleModule;
 import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
+import com.fasterxml.jackson.datatype.guava.GuavaModule;
 import com.fasterxml.jackson.datatype.joda.JodaModule;
 import com.google.common.base.Throwables;
 import com.metamx.common.Granularity;
@@ -171,10 +172,11 @@ public class DefaultObjectMapper extends ObjectMapper
         }
     );
     registerModule(serializerModule);
+    registerModule(new GuavaModule());
 
     configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
     configure(MapperFeature.AUTO_DETECT_GETTERS, false);
-    configure(MapperFeature.AUTO_DETECT_CREATORS, false);
+//    configure(MapperFeature.AUTO_DETECT_CREATORS, false); https://github.com/FasterXML/jackson-databind/issues/170
     configure(MapperFeature.AUTO_DETECT_FIELDS, false);
     configure(MapperFeature.AUTO_DETECT_IS_GETTERS, false);
     configure(MapperFeature.AUTO_DETECT_SETTERS, false);

common/src/main/java/com/metamx/druid/utils/CompressionUtils.java

@@ -0,0 +1,126 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.utils;
+
+import com.google.common.io.ByteStreams;
+import com.google.common.io.Closeables;
+import com.google.common.io.Files;
+import com.metamx.common.ISE;
+import com.metamx.common.StreamUtils;
+import com.metamx.common.logger.Logger;
+import sun.misc.IOUtils;
+
+import java.io.BufferedInputStream;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.util.zip.GZIPInputStream;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+import java.util.zip.ZipOutputStream;
+
+/**
+ */
+public class CompressionUtils
+{
+  private static final Logger log = new Logger(CompressionUtils.class);
+
+  public static long zip(File directory, File outputZipFile) throws IOException
+  {
+    if (!directory.isDirectory()) {
+      throw new IOException(String.format("directory[%s] is not a directory", directory));
+    }
+
+    if (!outputZipFile.getName().endsWith(".zip")) {
+      log.warn("No .zip suffix[%s], putting files from [%s] into it anyway.", outputZipFile, directory);
+    }
+
+    long totalSize = 0;
+    ZipOutputStream zipOut = null;
+    try {
+      zipOut = new ZipOutputStream(new FileOutputStream(outputZipFile));
+      File[] files = directory.listFiles();
+      for (File file : files) {
+        log.info("Adding file[%s] with size[%,d].  Total size[%,d]", file, file.length(), totalSize);
+        if (file.length() >= Integer.MAX_VALUE) {
+          zipOut.close();
+          outputZipFile.delete();
+          throw new IOException(String.format("file[%s] too large [%,d]", file, file.length()));
+        }
+        zipOut.putNextEntry(new ZipEntry(file.getName()));
+        totalSize += ByteStreams.copy(Files.newInputStreamSupplier(file), zipOut);
+      }
+    }
+    finally {
+      Closeables.closeQuietly(zipOut);
+    }
+
+    return totalSize;
+  }
+
+  public static void unzip(File pulledFile, File outDir) throws IOException
+  {
+    if (!(outDir.exists() && outDir.isDirectory())) {
+      throw new ISE("outDir[%s] must exist and be a directory", outDir);
+    }
+
+    log.info("Unzipping file[%s] to [%s]", pulledFile, outDir);
+    InputStream in = null;
+    try {
+      in = new BufferedInputStream(new FileInputStream(pulledFile));
+      unzip(in, outDir);
+    }
+    finally {
+      Closeables.closeQuietly(in);
+    }
+  }
+
+  public static void unzip(InputStream in, File outDir) throws IOException
+  {
+    ZipInputStream zipIn = new ZipInputStream(in);
+
+    ZipEntry entry;
+    while ((entry = zipIn.getNextEntry()) != null) {
+      OutputStream out = null;
+      try {
+        out = new FileOutputStream(new File(outDir, entry.getName()));
+        ByteStreams.copy(zipIn, out);
+        zipIn.closeEntry();
+      }
+      finally {
+        Closeables.closeQuietly(out);
+      }
+    }
+  }
+
+  public static void gunzip(File pulledFile, File outDir) throws IOException
+  {
+    log.info("Gunzipping file[%s] to [%s]", pulledFile, outDir);
+    StreamUtils.copyToFileAndClose(new GZIPInputStream(new FileInputStream(pulledFile)), outDir);
+    if (!pulledFile.delete()) {
+      log.error("Could not delete tmpFile[%s].", pulledFile);
+    }
+  }
+
+}

common/src/main/java/com/metamx/druid/utils/JodaUtils.java

@@ -19,12 +19,15 @@
 
 package com.metamx.druid.utils;
 
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
 import com.metamx.common.guava.Comparators;
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
+import javax.annotation.Nullable;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.TreeSet;
@@ -63,6 +66,17 @@ public class JodaUtils
     return retVal;
   }
 
+  public static boolean overlaps(final Interval i, Iterable<Interval> intervals) {
+    return Iterables.any(intervals, new Predicate<Interval>()
+    {
+      @Override
+      public boolean apply(@Nullable Interval input)
+      {
+        return input.overlaps(i);
+      }
+    });
+  }
+
   public static DateTime minDateTime(DateTime... times)
   {
     if (times == null) {

druid-services/pom.xml

@@ -24,11 +24,11 @@
     <artifactId>druid-services</artifactId>
     <name>druid-services</name>
     <description>druid-services</description>
-    <version>0.2.10-SNAPSHOT</version>
+    <version>0.3.4-SNAPSHOT</version>
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>
@@ -66,4 +66,4 @@
             </plugin>
         </plugins>
     </build>
-</project>
+</project>

examples/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <modules>

examples/rand/pom.xml

@@ -9,7 +9,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid-examples</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>

examples/rand/src/main/java/druid/examples/RealtimeStandaloneMain.java

@@ -12,7 +12,7 @@ import com.metamx.druid.log.LogLevelAdjuster;
 import com.metamx.druid.realtime.MetadataUpdater;
 import com.metamx.druid.realtime.MetadataUpdaterConfig;
 import com.metamx.druid.realtime.RealtimeNode;
-import com.metamx.druid.loading.SegmentPusher;
+import com.metamx.druid.loading.DataSegmentPusher;
 import com.metamx.phonebook.PhoneBook;
 
 
@@ -72,8 +72,8 @@ public class RealtimeStandaloneMain
     // dummyMetadataUpdater will not send updates to db because standalone demo has no db
     rn.setMetadataUpdater(dummyMetadataUpdater);
 
-    rn.setSegmentPusher(
-        new SegmentPusher()
+    rn.setDataSegmentPusher(
+        new DataSegmentPusher()
         {
           @Override
           public DataSegment push(File file, DataSegment segment) throws IOException

examples/twitter/pom.xml

@@ -9,7 +9,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid-examples</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>

examples/twitter/src/main/java/druid/examples/RealtimeStandaloneMain.java

@@ -12,7 +12,7 @@ import com.metamx.druid.log.LogLevelAdjuster;
 import com.metamx.druid.realtime.MetadataUpdater;
 import com.metamx.druid.realtime.MetadataUpdaterConfig;
 import com.metamx.druid.realtime.RealtimeNode;
-import com.metamx.druid.loading.SegmentPusher;
+import com.metamx.druid.loading.DataSegmentPusher;
 import com.metamx.phonebook.PhoneBook;
 import druid.examples.twitter.TwitterSpritzerFirehoseFactory;
 
@@ -48,10 +48,12 @@ public class RealtimeStandaloneMain
 
     rn.setPhoneBook(dummyPhoneBook);
     MetadataUpdater dummyMetadataUpdater =
-        new MetadataUpdater(new DefaultObjectMapper(),
+        new MetadataUpdater(
+            new DefaultObjectMapper(),
             Config.createFactory(Initialization.loadProperties()).build(MetadataUpdaterConfig.class),
             dummyPhoneBook,
-            null) {
+            null
+        ) {
           @Override
           public void publishSegment(DataSegment segment) throws IOException
           {
@@ -74,8 +76,8 @@ public class RealtimeStandaloneMain
     // dummyMetadataUpdater will not send updates to db because standalone demo has no db
     rn.setMetadataUpdater(dummyMetadataUpdater);
 
-    rn.setSegmentPusher(
-        new SegmentPusher()
+    rn.setDataSegmentPusher(
+        new DataSegmentPusher()
         {
           @Override
           public DataSegment push(File file, DataSegment segment) throws IOException

examples/twitter/src/main/java/druid/examples/twitter/TwitterSpritzerFirehoseFactory.java

@@ -62,7 +62,7 @@ import static java.lang.Thread.sleep;
  *  Notes on JSON parsing: as of twitter4j 2.2.x, the json parser has some bugs (ex: Status.toString()
  *  can have number format exceptions), so it might be necessary to extract raw json and process it
  *  separately.  If so, set twitter4.jsonStoreEnabled=true and look at DataObjectFactory#getRawJSON();
- *  org.codehaus.jackson.map.ObjectMapper should be used to parse.
+ *  com.fasterxml.jackson.databind.ObjectMapper should be used to parse.
  * @author pbaclace
  */
 @JsonTypeName("twitzer")

index-common/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>
@@ -94,4 +94,4 @@
             </plugin>
         </plugins>
     </build>
-</project>
+</project>

index-common/src/main/java/com/metamx/druid/index/column/SimpleColumn.java

@@ -72,30 +72,30 @@ class SimpleColumn implements Column
   @Override
   public DictionaryEncodedColumn getDictionaryEncoding()
   {
-    return dictionaryEncodedColumn.get();
+    return dictionaryEncodedColumn == null ? null : dictionaryEncodedColumn.get();
   }
 
   @Override
   public RunLengthColumn getRunLengthColumn()
   {
-    return runLengthColumn.get();
+    return runLengthColumn == null ? null : runLengthColumn.get();
   }
 
   @Override
   public GenericColumn getGenericColumn()
   {
-    return genericColumn.get();
+    return genericColumn == null ? null : genericColumn.get();
   }
 
   @Override
   public ComplexColumn getComplexColumn()
   {
-    return complexColumn.get();
+    return complexColumn == null ? null : complexColumn.get();
   }
 
   @Override
   public BitmapIndex getBitmapIndex()
   {
-    return bitmapIndex.get();
+    return bitmapIndex == null ? null : bitmapIndex.get();
   }
 }

indexer/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>
@@ -57,14 +57,6 @@
                     <groupId>javax.mail</groupId>
                     <artifactId>mail</artifactId>
                 </exclusion>
-                <exclusion>
-                    <groupId>org.codehaus.jackson</groupId>
-                    <artifactId>jackson-core-asl</artifactId>
-                </exclusion>
-                <exclusion>
-                    <groupId>org.codehaus.jackson</groupId>
-                    <artifactId>jackson-mapper-asl</artifactId>
-                </exclusion>
             </exclusions>
         </dependency>
         <dependency>

indexer/src/main/java/com/metamx/druid/indexer/DeterminePartitionsJob.java

@@ -266,8 +266,7 @@ public class DeterminePartitionsJob implements Jobby
         Context context
     ) throws IOException, InterruptedException
     {
-      // Create group key
-      // TODO -- There are more efficient ways to do this
+      // Create group key, there are probably more efficient ways of doing this
       final Map<String, Set<String>> dims = Maps.newTreeMap();
       for(final String dim : inputRow.getDimensions()) {
         final Set<String> dimValues = ImmutableSortedSet.copyOf(inputRow.getDimension(dim));
@@ -394,6 +393,9 @@ public class DeterminePartitionsJob implements Jobby
       final Interval interval = maybeInterval.get();
       final byte[] groupKey = interval.getStart().toString().getBytes(Charsets.UTF_8);
 
+      // Emit row-counter value.
+      write(context, groupKey, new DimValueCount("", "", 1));
+
       for(final Map.Entry<String, Iterable<String>> dimAndValues : dims.entrySet()) {
         final String dim = dimAndValues.getKey();
 
@@ -510,9 +512,23 @@ public class DeterminePartitionsJob implements Jobby
         Context context, SortableBytes keyBytes, Iterable<DimValueCount> combinedIterable
     ) throws IOException, InterruptedException
     {
-      PeekingIterator<DimValueCount> iterator = Iterators.peekingIterator(combinedIterable.iterator());
+      final DateTime bucket = new DateTime(new String(keyBytes.getGroupKey(), Charsets.UTF_8));
+      final PeekingIterator<DimValueCount> iterator = Iterators.peekingIterator(combinedIterable.iterator());
 
-      // "iterator" will take us over many candidate dimensions
+      log.info(
+          "Determining partitions for interval: %s",
+          config.getGranularitySpec().bucketInterval(bucket).orNull()
+      );
+
+      // First DVC should be the total row count indicator
+      final DimValueCount firstDvc = iterator.next();
+      final int totalRows = firstDvc.numRows;
+
+      if(!firstDvc.dim.equals("") || !firstDvc.value.equals("")) {
+        throw new IllegalStateException("WTF?! Expected total row indicator on first k/v pair!");
+      }
+
+      // "iterator" will now take us over many candidate dimensions
       DimPartitions currentDimPartitions = null;
       DimPartition currentDimPartition = null;
       String currentDimPartitionStart = null;
@@ -636,8 +652,6 @@ public class DeterminePartitionsJob implements Jobby
         throw new ISE("No suitable partitioning dimension found!");
       }
 
-      final int totalRows = dimPartitionss.values().iterator().next().getRows();
-
       int maxCardinality = Integer.MIN_VALUE;
       long minVariance = Long.MAX_VALUE;
       DimPartitions minVariancePartitions = null;
@@ -645,12 +659,14 @@ public class DeterminePartitionsJob implements Jobby
 
       for(final DimPartitions dimPartitions : dimPartitionss.values()) {
         if(dimPartitions.getRows() != totalRows) {
-          throw new ISE(
-              "WTF?! Dimension[%s] row count %,d != expected row count %,d",
+          log.info(
+              "Dimension[%s] is not present in all rows (row count %,d != expected row count %,d)",
               dimPartitions.dim,
               dimPartitions.getRows(),
               totalRows
           );
+
+          continue;
         }
 
         // Make sure none of these shards are oversized
@@ -684,7 +700,6 @@ public class DeterminePartitionsJob implements Jobby
         throw new ISE("No suitable partitioning dimension found!");
       }
 
-      final DateTime bucket = new DateTime(new String(keyBytes.getGroupKey(), Charsets.UTF_8));
       final OutputStream out = Utils.makePathAndOutputStream(
           context, config.makeSegmentPartitionInfoPath(new Bucket(0, bucket, 0)), config.isOverwriteFiles()
       );

indexer/src/main/java/com/metamx/druid/indexer/HadoopDruidIndexerConfig.java

@@ -662,8 +662,9 @@ public class HadoopDruidIndexerConfig
 
     return new Path(
         String.format(
-            "%s/%s_%s/%s/%s",
+            "%s/%s/%s_%s/%s/%s",
             getSegmentOutputDir(),
+            dataSource,
             bucketInterval.getStart().toString(),
             bucketInterval.getEnd().toString(),
             getVersion().toString(),

indexer/src/main/java/com/metamx/druid/indexer/IndexGeneratorJob.java

@@ -379,7 +379,8 @@ public class IndexGeneratorJob implements Jobby
         );
       } else if (outputFS instanceof LocalFileSystem) {
         loadSpec = ImmutableMap.<String, Object>of(
-            "type", "test"
+            "type", "local",
+            "path", indexOutURI.getPath()
         );
       } else {
         throw new ISE("Unknown file system[%s]", outputFS.getClass());

merger/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.metamx</groupId>
         <artifactId>druid</artifactId>
-        <version>0.2.10-SNAPSHOT</version>
+        <version>0.3.4-SNAPSHOT</version>
     </parent>
 
     <dependencies>

merger/src/main/java/com/metamx/druid/merger/common/TaskCallback.java

@@ -17,9 +17,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
-package com.metamx.druid.merger.coordinator;
-
-import com.metamx.druid.merger.common.TaskStatus;
+package com.metamx.druid.merger.common;
 
 public interface TaskCallback
 {

merger/src/main/java/com/metamx/druid/merger/common/TaskHolder.java

@@ -1,57 +0,0 @@
-/*
- * Druid - a distributed column store.
- * Copyright (C) 2012  Metamarkets Group Inc.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
- */
-
-package com.metamx.druid.merger.common;
-
-import com.fasterxml.jackson.annotation.JsonCreator;
-import com.fasterxml.jackson.annotation.JsonProperty;
-import com.metamx.druid.merger.common.task.Task;
-import com.metamx.druid.merger.coordinator.TaskContext;
-
-
-
-/**
- */
-public class TaskHolder
-{
-  private final Task task;
-  private final TaskContext taskContext;
-
-  @JsonCreator
-  public TaskHolder(
-      @JsonProperty("task") Task task,
-      @JsonProperty("taskContext") TaskContext taskContext
-  )
-  {
-    this.task = task;
-    this.taskContext = taskContext;
-  }
-
-  @JsonProperty
-  public Task getTask()
-  {
-    return task;
-  }
-
-  @JsonProperty
-  public TaskContext getTaskContext()
-  {
-    return taskContext;
-  }
-}

merger/src/main/java/com/metamx/druid/merger/common/TaskLock.java

@@ -17,40 +17,30 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
-package com.metamx.druid.merger.coordinator;
+package com.metamx.druid.merger.common;
 
-import com.google.common.base.Function;
 import com.google.common.base.Objects;
-import com.google.common.collect.Iterables;
-import com.google.common.collect.Lists;
-import com.google.common.collect.Ordering;
-import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import org.joda.time.Interval;
 
-import java.util.Set;
-import java.util.TreeSet;
-
 /**
- * Represents a transaction as well as the lock it holds. Not immutable: the task set can change.
+ * Represents a lock held by some task. Immutable.
  */
-public class TaskGroup
+public class TaskLock
 {
   private final String groupId;
   private final String dataSource;
   private final Interval interval;
   private final String version;
-  private final Set<Task> taskSet = new TreeSet<Task>(
-      new Ordering<Task>()
-      {
-        @Override
-        public int compare(Task task, Task task1)
-        {
-          return task.getId().compareTo(task1.getId());
-        }
-      }.nullsFirst()
-  );
 
-  public TaskGroup(String groupId, String dataSource, Interval interval, String version)
+  @JsonCreator
+  public TaskLock(
+      @JsonProperty("groupId") String groupId,
+      @JsonProperty("dataSource") String dataSource,
+      @JsonProperty("interval") Interval interval,
+      @JsonProperty("version") String version
+  )
   {
     this.groupId = groupId;
     this.dataSource = dataSource;
@@ -58,29 +48,48 @@ public class TaskGroup
     this.version = version;
   }
 
+  @JsonProperty
   public String getGroupId()
   {
     return groupId;
   }
 
+  @JsonProperty
   public String getDataSource()
   {
     return dataSource;
   }
 
+  @JsonProperty
   public Interval getInterval()
   {
     return interval;
   }
 
+  @JsonProperty
   public String getVersion()
   {
     return version;
   }
 
-  public Set<Task> getTaskSet()
+  @Override
+  public boolean equals(Object o)
   {
-    return taskSet;
+    if (!(o instanceof TaskLock)) {
+      return false;
+    } else {
+      final TaskLock x = (TaskLock) o;
+      return Objects.equal(this.groupId, x.groupId) &&
+             Objects.equal(this.dataSource, x.dataSource) &&
+             Objects.equal(this.interval, x.interval) &&
+             Objects.equal(this.version, x.version);
+    }
+  }
+
+  @Override
+  public int hashCode()
+  {
+    return Objects.hashCode(groupId, dataSource, interval, version);
   }
 
   @Override
@@ -91,21 +100,6 @@ public class TaskGroup
                   .add("dataSource", dataSource)
                   .add("interval", interval)
                   .add("version", version)
-                  .add(
-                      "taskSet",
-                      Lists.newArrayList(
-                          Iterables.transform(
-                              taskSet, new Function<Task, Object>()
-                          {
-                            @Override
-                            public Object apply(Task task)
-                            {
-                              return task.getId();
-                            }
-                          }
-                          )
-                      )
-                  )
                   .toString();
   }
 }

merger/src/main/java/com/metamx/druid/merger/common/TaskStatus.java

@@ -20,64 +20,42 @@
 package com.metamx.druid.merger.common;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonIgnore;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.common.base.Objects;
 import com.google.common.base.Preconditions;
-import com.google.common.collect.ImmutableList;
-import com.metamx.druid.client.DataSegment;
-import com.metamx.druid.merger.common.task.Task;
-
-
-
-import java.util.Collections;
-import java.util.List;
 
+/**
+ * Represents the status of a task. The task may be ongoing ({@link #isComplete()} false) or it may be
+ * complete ({@link #isComplete()} true).
+ * <p/>
+ * TaskStatus objects are immutable.
+ */
 public class TaskStatus
 {
   public static enum Status
   {
     RUNNING,
     SUCCESS,
-    FAILED,
-    CONTINUED
+    FAILED
   }
 
   public static TaskStatus running(String taskId)
   {
-    return new TaskStatus(
-        taskId,
-        Status.RUNNING,
-        Collections.<DataSegment>emptyList(),
-        Collections.<Task>emptyList(),
-        -1
-    );
+    return new TaskStatus(taskId, Status.RUNNING, -1);
+  }
+
+  public static TaskStatus success(String taskId)
+  {
+    return new TaskStatus(taskId, Status.SUCCESS, -1);
   }
 
   public static TaskStatus failure(String taskId)
   {
-    return new TaskStatus(taskId, Status.FAILED, Collections.<DataSegment>emptyList(), Collections.<Task>emptyList(), -1);
-  }
-
-  public static TaskStatus success(String taskId, List<DataSegment> segments)
-  {
-    return new TaskStatus(taskId, Status.SUCCESS, ImmutableList.copyOf(segments), Collections.<Task>emptyList(), -1);
-  }
-
-  public static TaskStatus continued(String taskId, List<Task> nextTasks)
-  {
-    Preconditions.checkArgument(nextTasks.size() > 0, "nextTasks.size() > 0");
-    return new TaskStatus(
-        taskId,
-        Status.CONTINUED,
-        Collections.<DataSegment>emptyList(),
-        ImmutableList.copyOf(nextTasks),
-        -1
-    );
+    return new TaskStatus(taskId, Status.FAILED, -1);
   }
 
   private final String id;
-  private final List<DataSegment> segments;
-  private final List<Task> nextTasks;
   private final Status status;
   private final long duration;
 
@@ -85,16 +63,16 @@ public class TaskStatus
   private TaskStatus(
       @JsonProperty("id") String id,
       @JsonProperty("status") Status status,
-      @JsonProperty("segments") List<DataSegment> segments,
-      @JsonProperty("nextTasks") List<Task> nextTasks,
       @JsonProperty("duration") long duration
   )
   {
     this.id = id;
-    this.segments = segments;
-    this.nextTasks = nextTasks;
     this.status = status;
     this.duration = duration;
+
+    // Check class invariants.
+    Preconditions.checkNotNull(id, "id");
+    Preconditions.checkNotNull(status, "status");
   }
 
   @JsonProperty("id")
@@ -109,18 +87,6 @@ public class TaskStatus
     return status;
   }
 
-  @JsonProperty("segments")
-  public List<DataSegment> getSegments()
-  {
-    return segments;
-  }
-
-  @JsonProperty("nextTasks")
-  public List<Task> getNextTasks()
-  {
-    return nextTasks;
-  }
-
   @JsonProperty("duration")
   public long getDuration()
   {
@@ -129,43 +95,38 @@ public class TaskStatus
 
   /**
    * Signals that a task is not yet complete, and is still runnable on a worker. Exactly one of isRunnable,
-   * isContinued, isSuccess, or isFailure will be true at any one time.
+   * isSuccess, or isFailure will be true at any one time.
    */
+  @JsonIgnore
   public boolean isRunnable()
   {
     return status == Status.RUNNING;
   }
 
-  /**
-   * Returned by tasks when they complete successfully without spawning subtasks. Exactly one of isRunnable,
-   * isContinued, isSuccess, or isFailure will be true at any one time.
-   */
-  public boolean isContinued()
-  {
-    return status == Status.CONTINUED;
-  }
-
   /**
    * Inverse of {@link #isRunnable}.
    */
+  @JsonIgnore
   public boolean isComplete()
   {
     return !isRunnable();
   }
 
   /**
-   * Returned by tasks when they spawn subtasks. Exactly one of isRunnable, isContinued, isSuccess, or isFailure will
+   * Returned by tasks when they spawn subtasks. Exactly one of isRunnable, isSuccess, or isFailure will
    * be true at any one time.
    */
+  @JsonIgnore
   public boolean isSuccess()
   {
     return status == Status.SUCCESS;
   }
 
   /**
-   * Returned by tasks when they complete unsuccessfully. Exactly one of isRunnable, isContinued, isSuccess, or
+   * Returned by tasks when they complete unsuccessfully. Exactly one of isRunnable, isSuccess, or
    * isFailure will be true at any one time.
    */
+  @JsonIgnore
   public boolean isFailure()
   {
     return status == Status.FAILED;
@@ -173,7 +134,7 @@ public class TaskStatus
 
   public TaskStatus withDuration(long _duration)
   {
-    return new TaskStatus(id, status, segments, nextTasks, _duration);
+    return new TaskStatus(id, status, _duration);
   }
 
   @Override
@@ -181,8 +142,6 @@ public class TaskStatus
   {
     return Objects.toStringHelper(this)
                   .add("id", id)
-                  .add("segments", segments)
-                  .add("nextTasks", nextTasks)
                   .add("status", status)
                   .add("duration", duration)
                   .toString();

merger/src/main/java/com/metamx/druid/merger/common/TaskToolbox.java

@@ -20,19 +20,23 @@
 package com.metamx.druid.merger.common;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
-import com.google.common.collect.ImmutableMap;
-import com.metamx.druid.loading.S3SegmentPuller;
-import com.metamx.druid.loading.S3SegmentGetterConfig;
-import com.metamx.druid.loading.S3ZippedSegmentPuller;
-import com.metamx.druid.loading.SegmentPuller;
+import com.google.common.collect.Maps;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.loading.DataSegmentPusher;
+import com.metamx.druid.loading.MMappedQueryableIndexFactory;
+import com.metamx.druid.loading.S3DataSegmentPuller;
+import com.metamx.druid.loading.SegmentKiller;
+import com.metamx.druid.loading.SegmentLoaderConfig;
+import com.metamx.druid.loading.SegmentLoadingException;
+import com.metamx.druid.loading.SingleSegmentLoader;
+import com.metamx.druid.merger.common.actions.TaskActionClient;
+import com.metamx.druid.merger.common.config.TaskConfig;
 import com.metamx.druid.merger.common.task.Task;
-import com.metamx.druid.merger.coordinator.config.IndexerCoordinatorConfig;
-import com.metamx.druid.loading.SegmentPusher;
 import com.metamx.emitter.service.ServiceEmitter;
-
 import org.jets3t.service.impl.rest.httpclient.RestS3Service;
 
 import java.io.File;
+import java.util.List;
 import java.util.Map;
 
 /**
@@ -40,67 +44,84 @@ import java.util.Map;
  */
 public class TaskToolbox
 {
-  private final IndexerCoordinatorConfig config;
+  private final TaskConfig config;
+  private final TaskActionClient taskActionClient;
   private final ServiceEmitter emitter;
   private final RestS3Service s3Client;
-  private final SegmentPusher segmentPusher;
+  private final DataSegmentPusher segmentPusher;
+  private final SegmentKiller segmentKiller;
   private final ObjectMapper objectMapper;
 
   public TaskToolbox(
-      IndexerCoordinatorConfig config,
+      TaskConfig config,
+      TaskActionClient taskActionClient,
       ServiceEmitter emitter,
       RestS3Service s3Client,
-      SegmentPusher segmentPusher,
+      DataSegmentPusher segmentPusher,
+      SegmentKiller segmentKiller,
       ObjectMapper objectMapper
   )
   {
     this.config = config;
+    this.taskActionClient = taskActionClient;
     this.emitter = emitter;
     this.s3Client = s3Client;
     this.segmentPusher = segmentPusher;
+    this.segmentKiller = segmentKiller;
     this.objectMapper = objectMapper;
   }
 
-  public IndexerCoordinatorConfig getConfig()
+  public TaskConfig getConfig()
   {
     return config;
   }
 
+  public TaskActionClient getTaskActionClient()
+  {
+    return taskActionClient;
+  }
+
   public ServiceEmitter getEmitter()
   {
     return emitter;
   }
 
-  public RestS3Service getS3Client()
-  {
-    return s3Client;
-  }
-
-  public SegmentPusher getSegmentPusher()
+  public DataSegmentPusher getSegmentPusher()
   {
     return segmentPusher;
   }
 
+  public SegmentKiller getSegmentKiller()
+  {
+    return segmentKiller;
+  }
+
   public ObjectMapper getObjectMapper()
   {
     return objectMapper;
   }
 
-  public Map<String, SegmentPuller> getSegmentGetters(final Task task)
+  public Map<DataSegment, File> getSegments(final Task task, List<DataSegment> segments)
+      throws SegmentLoadingException
   {
-    final S3SegmentGetterConfig getterConfig = new S3SegmentGetterConfig()
-    {
-      @Override
-      public File getCacheDirectory()
-      {
-        return new File(config.getTaskDir(task), "fetched_segments");
-      }
-    };
+    final SingleSegmentLoader loader = new SingleSegmentLoader(
+        new S3DataSegmentPuller(s3Client),
+        new MMappedQueryableIndexFactory(),
+        new SegmentLoaderConfig()
+        {
+          @Override
+          public File getCacheDirectory()
+          {
+            return new File(config.getTaskDir(task), "fetched_segments");
+          }
+        }
+    );
 
-    return ImmutableMap.<String, SegmentPuller>builder()
-                       .put("s3", new S3SegmentPuller(s3Client, getterConfig))
-                       .put("s3_union", new S3SegmentPuller(s3Client, getterConfig))
-                       .put("s3_zip", new S3ZippedSegmentPuller(s3Client, getterConfig))
-                       .build();
+    Map<DataSegment, File> retVal = Maps.newLinkedHashMap();
+    for (DataSegment segment : segments) {
+      retVal.put(segment, loader.getSegmentFiles(segment));
+    }
+
+    return retVal;
   }
 }

merger/src/main/java/com/metamx/druid/merger/common/actions/LocalTaskActionClient.java

@@ -0,0 +1,37 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.metamx.druid.merger.coordinator.TaskStorage;
+import com.metamx.emitter.EmittingLogger;
+
+public class LocalTaskActionClient implements TaskActionClient
+{
+  private final TaskStorage storage;
+  private final TaskActionToolbox toolbox;
+
+  private static final EmittingLogger log = new EmittingLogger(LocalTaskActionClient.class);
+
+  public LocalTaskActionClient(TaskStorage storage, TaskActionToolbox toolbox)
+  {
+    this.storage = storage;
+    this.toolbox = toolbox;
+  }
+
+  @Override
+  public <RetType> RetType submit(TaskAction<RetType> taskAction)
+  {
+    final RetType ret = taskAction.perform(toolbox);
+
+    // Add audit log
+    try {
+      storage.addAuditLog(taskAction);
+    }
+    catch (Exception e) {
+      log.makeAlert(e, "Failed to record action in audit log")
+         .addData("task", taskAction.getTask().getId())
+         .addData("actionClass", taskAction.getClass().getName())
+         .emit();
+    }
+
+    return ret;
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/LockAcquireAction.java

@@ -0,0 +1,53 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Optional;
+import com.google.common.base.Throwables;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+import org.joda.time.Interval;
+
+public class LockAcquireAction implements TaskAction<Optional<TaskLock>>
+{
+  private final Task task;
+  private final Interval interval;
+
+  @JsonCreator
+  public LockAcquireAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("interval") Interval interval
+  )
+  {
+    this.task = task;
+    this.interval = interval;
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public Interval getInterval()
+  {
+    return interval;
+  }
+
+  public TypeReference<Optional<TaskLock>> getReturnTypeReference()
+  {
+    return new TypeReference<Optional<TaskLock>>() {};
+  }
+
+  @Override
+  public Optional<TaskLock> perform(TaskActionToolbox toolbox)
+  {
+    try {
+      return toolbox.getTaskLockbox().tryLock(task, interval);
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/LockListAction.java

@@ -0,0 +1,45 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Optional;
+import com.google.common.base.Throwables;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+
+import java.util.List;
+
+public class LockListAction implements TaskAction<List<TaskLock>>
+{
+  private final Task task;
+
+  @JsonCreator
+  public LockListAction(
+      @JsonProperty("task") Task task
+  )
+  {
+    this.task = task;
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  public TypeReference<List<TaskLock>> getReturnTypeReference()
+  {
+    return new TypeReference<List<TaskLock>>() {};
+  }
+
+  @Override
+  public List<TaskLock> perform(TaskActionToolbox toolbox)
+  {
+    try {
+      return toolbox.getTaskLockbox().findLocksForTask(task);
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/LockReleaseAction.java

@@ -0,0 +1,55 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Throwables;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+import org.joda.time.Interval;
+
+import java.util.List;
+
+public class LockReleaseAction implements TaskAction<Void>
+{
+  private final Task task;
+  private final Interval interval;
+
+  @JsonCreator
+  public LockReleaseAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("interval") Interval interval
+  )
+  {
+    this.task = task;
+    this.interval = interval;
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public Interval getInterval()
+  {
+    return interval;
+  }
+
+  public TypeReference<Void> getReturnTypeReference()
+  {
+    return new TypeReference<Void>() {};
+  }
+
+  @Override
+  public Void perform(TaskActionToolbox toolbox)
+  {
+    try {
+      toolbox.getTaskLockbox().unlock(task, interval);
+      return null;
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/RemoteTaskActionClient.java

@@ -0,0 +1,75 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.google.common.base.Charsets;
+import com.google.common.base.Throwables;
+import com.metamx.common.logger.Logger;
+import com.metamx.http.client.HttpClient;
+import com.metamx.http.client.response.ToStringResponseHandler;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.netflix.curator.x.discovery.ServiceInstance;
+import com.netflix.curator.x.discovery.ServiceProvider;
+
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.util.Map;
+
+public class RemoteTaskActionClient implements TaskActionClient
+{
+  private final HttpClient httpClient;
+  private final ServiceProvider serviceProvider;
+  private final ObjectMapper jsonMapper;
+
+  private static final Logger log = new Logger(RemoteTaskActionClient.class);
+
+  public RemoteTaskActionClient(HttpClient httpClient, ServiceProvider serviceProvider, ObjectMapper jsonMapper)
+  {
+    this.httpClient = httpClient;
+    this.serviceProvider = serviceProvider;
+    this.jsonMapper = jsonMapper;
+  }
+
+  @Override
+  public <RetType> RetType submit(TaskAction<RetType> taskAction)
+  {
+    try {
+      byte[] dataToSend = jsonMapper.writeValueAsBytes(taskAction);
+
+      final String response = httpClient.post(getServiceUri().toURL())
+                                        .setContent("application/json", dataToSend)
+                                        .go(new ToStringResponseHandler(Charsets.UTF_8))
+                                        .get();
+
+      final Map<String, Object> responseDict = jsonMapper.readValue(
+          response,
+          new TypeReference<Map<String, Object>>() {}
+      );
+
+      return jsonMapper.convertValue(responseDict.get("result"), taskAction.getReturnTypeReference());
+    }
+    catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+
+  private URI getServiceUri() throws Exception
+  {
+    final ServiceInstance instance = serviceProvider.getInstance();
+    final String scheme;
+    final String host;
+    final int port;
+    final String path = "/mmx/merger/v1/action";
+
+    host = instance.getAddress();
+
+    if (instance.getSslPort() != null && instance.getSslPort() > 0) {
+      scheme = "https";
+      port = instance.getSslPort();
+    } else {
+      scheme = "http";
+      port = instance.getPort();
+    }
+
+    return new URI(scheme, null, host, port, path, null, null);
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/SegmentInsertAction.java

@@ -0,0 +1,76 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Predicate;
+import com.google.common.base.Throwables;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
+import com.metamx.common.ISE;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.metamx.emitter.service.ServiceMetricEvent;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+
+import java.util.List;
+import java.util.Set;
+
+public class SegmentInsertAction implements TaskAction<Void>
+{
+  private final Task task;
+  private final Set<DataSegment> segments;
+
+  @JsonCreator
+  public SegmentInsertAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("segments") Set<DataSegment> segments
+  )
+  {
+    this.task = task;
+    this.segments = ImmutableSet.copyOf(segments);
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public Set<DataSegment> getSegments()
+  {
+    return segments;
+  }
+
+  public TypeReference<Void> getReturnTypeReference()
+  {
+    return new TypeReference<Void>() {};
+  }
+
+  @Override
+  public Void perform(TaskActionToolbox toolbox)
+  {
+    if(!toolbox.taskLockCoversSegments(task, segments, false)) {
+      throw new ISE("Segments not covered by locks for task: %s", task.getId());
+    }
+
+    try {
+      toolbox.getMergerDBCoordinator().announceHistoricalSegments(segments);
+
+      // Emit metrics
+      final ServiceMetricEvent.Builder metricBuilder = new ServiceMetricEvent.Builder()
+          .setUser2(task.getDataSource())
+          .setUser4(task.getType());
+
+      for (DataSegment segment : segments) {
+        metricBuilder.setUser5(segment.getInterval().toString());
+        toolbox.getEmitter().emit(metricBuilder.build("indexer/segment/bytes", segment.getSize()));
+      }
+
+      return null;
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/SegmentListUnusedAction.java

@@ -0,0 +1,63 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Throwables;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+import org.joda.time.Interval;
+
+import java.util.List;
+
+public class SegmentListUnusedAction implements TaskAction<List<DataSegment>>
+{
+  private final Task task;
+  private final String dataSource;
+  private final Interval interval;
+
+  @JsonCreator
+  public SegmentListUnusedAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("dataSource") String dataSource,
+      @JsonProperty("interval") Interval interval
+  )
+  {
+    this.task = task;
+    this.dataSource = dataSource;
+    this.interval = interval;
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public String getDataSource()
+  {
+    return dataSource;
+  }
+
+  @JsonProperty
+  public Interval getInterval()
+  {
+    return interval;
+  }
+
+  public TypeReference<List<DataSegment>> getReturnTypeReference()
+  {
+    return new TypeReference<List<DataSegment>>() {};
+  }
+
+  @Override
+  public List<DataSegment> perform(TaskActionToolbox toolbox)
+  {
+    try {
+      return toolbox.getMergerDBCoordinator().getUnusedSegmentsForInterval(dataSource, interval);
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/SegmentListUsedAction.java

@@ -0,0 +1,63 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Throwables;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+import org.joda.time.Interval;
+
+import java.util.List;
+
+public class SegmentListUsedAction implements TaskAction<List<DataSegment>>
+{
+  private final Task task;
+  private final String dataSource;
+  private final Interval interval;
+
+  @JsonCreator
+  public SegmentListUsedAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("dataSource") String dataSource,
+      @JsonProperty("interval") Interval interval
+  )
+  {
+    this.task = task;
+    this.dataSource = dataSource;
+    this.interval = interval;
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public String getDataSource()
+  {
+    return dataSource;
+  }
+
+  @JsonProperty
+  public Interval getInterval()
+  {
+    return interval;
+  }
+
+  public TypeReference<List<DataSegment>> getReturnTypeReference()
+  {
+    return new TypeReference<List<DataSegment>>() {};
+  }
+
+  @Override
+  public List<DataSegment> perform(TaskActionToolbox toolbox)
+  {
+    try {
+      return toolbox.getMergerDBCoordinator().getUsedSegmentsForInterval(dataSource, interval);
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/SegmentNukeAction.java

@@ -0,0 +1,76 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Predicate;
+import com.google.common.base.Throwables;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
+import com.metamx.common.ISE;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.metamx.emitter.service.ServiceMetricEvent;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+
+import java.util.List;
+import java.util.Set;
+
+public class SegmentNukeAction implements TaskAction<Void>
+{
+  private final Task task;
+  private final Set<DataSegment> segments;
+
+  @JsonCreator
+  public SegmentNukeAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("segments") Set<DataSegment> segments
+  )
+  {
+    this.task = task;
+    this.segments = ImmutableSet.copyOf(segments);
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public Set<DataSegment> getSegments()
+  {
+    return segments;
+  }
+
+  public TypeReference<Void> getReturnTypeReference()
+  {
+    return new TypeReference<Void>() {};
+  }
+
+  @Override
+  public Void perform(TaskActionToolbox toolbox)
+  {
+    if(!toolbox.taskLockCoversSegments(task, segments, true)) {
+      throw new ISE("Segments not covered by locks for task: %s", task.getId());
+    }
+
+    try {
+      toolbox.getMergerDBCoordinator().deleteSegments(segments);
+
+      // Emit metrics
+      final ServiceMetricEvent.Builder metricBuilder = new ServiceMetricEvent.Builder()
+          .setUser2(task.getDataSource())
+          .setUser4(task.getType());
+
+      for (DataSegment segment : segments) {
+        metricBuilder.setUser5(segment.getInterval().toString());
+        toolbox.getEmitter().emit(metricBuilder.build("indexer/segmentNuked/bytes", segment.getSize()));
+      }
+
+      return null;
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/SpawnTasksAction.java

@@ -0,0 +1,57 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Throwables;
+import com.google.common.collect.ImmutableList;
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import com.fasterxml.jackson.core.type.TypeReference;
+
+import java.util.List;
+
+public class SpawnTasksAction implements TaskAction<Void>
+{
+  private final Task task;
+  private final List<Task> newTasks;
+
+  @JsonCreator
+  public SpawnTasksAction(
+      @JsonProperty("task") Task task,
+      @JsonProperty("newTasks") List<Task> newTasks
+  )
+  {
+    this.task = task;
+    this.newTasks = ImmutableList.copyOf(newTasks);
+  }
+
+  @JsonProperty
+  public Task getTask()
+  {
+    return task;
+  }
+
+  @JsonProperty
+  public List<Task> getNewTasks()
+  {
+    return newTasks;
+  }
+
+  public TypeReference<Void> getReturnTypeReference()
+  {
+    return new TypeReference<Void>() {};
+  }
+
+  @Override
+  public Void perform(TaskActionToolbox toolbox)
+  {
+    try {
+      for(final Task newTask : newTasks) {
+        toolbox.getTaskQueue().add(newTask);
+      }
+
+      return null;
+    } catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/TaskAction.java

@@ -0,0 +1,24 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.metamx.druid.merger.common.task.Task;
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.fasterxml.jackson.core.type.TypeReference;
+
+@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type")
+@JsonSubTypes(value = {
+    @JsonSubTypes.Type(name = "lockAcquire", value = LockAcquireAction.class),
+    @JsonSubTypes.Type(name = "lockList", value = LockListAction.class),
+    @JsonSubTypes.Type(name = "lockRelease", value = LockReleaseAction.class),
+    @JsonSubTypes.Type(name = "segmentInsertion", value = SegmentInsertAction.class),
+    @JsonSubTypes.Type(name = "segmentListUsed", value = SegmentListUsedAction.class),
+    @JsonSubTypes.Type(name = "segmentListUnused", value = SegmentListUnusedAction.class),
+    @JsonSubTypes.Type(name = "segmentNuke", value = SegmentNukeAction.class),
+    @JsonSubTypes.Type(name = "spawnTasks", value = SpawnTasksAction.class)
+})
+public interface TaskAction<RetType>
+{
+  public Task getTask(); // TODO Look into replacing this with task ID so stuff serializes smaller
+  public TypeReference<RetType> getReturnTypeReference(); // T_T
+  public RetType perform(TaskActionToolbox toolbox);
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/TaskActionClient.java

@@ -0,0 +1,6 @@
+package com.metamx.druid.merger.common.actions;
+
+public interface TaskActionClient
+{
+  public <RetType> RetType submit(TaskAction<RetType> taskAction);
+}

merger/src/main/java/com/metamx/druid/merger/common/actions/TaskActionToolbox.java

@@ -0,0 +1,95 @@
+package com.metamx.druid.merger.common.actions;
+
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+import com.metamx.common.ISE;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.metamx.druid.merger.coordinator.MergerDBCoordinator;
+import com.metamx.druid.merger.coordinator.TaskLockbox;
+import com.metamx.druid.merger.coordinator.TaskQueue;
+import com.metamx.emitter.service.ServiceEmitter;
+
+import java.util.List;
+import java.util.Set;
+
+public class TaskActionToolbox
+{
+  private final TaskQueue taskQueue;
+  private final TaskLockbox taskLockbox;
+  private final MergerDBCoordinator mergerDBCoordinator;
+  private final ServiceEmitter emitter;
+
+  public TaskActionToolbox(
+      TaskQueue taskQueue,
+      TaskLockbox taskLockbox,
+      MergerDBCoordinator mergerDBCoordinator,
+      ServiceEmitter emitter
+  )
+  {
+    this.taskQueue = taskQueue;
+    this.taskLockbox = taskLockbox;
+    this.mergerDBCoordinator = mergerDBCoordinator;
+    this.emitter = emitter;
+  }
+
+  public TaskQueue getTaskQueue()
+  {
+    return taskQueue;
+  }
+
+  public TaskLockbox getTaskLockbox()
+  {
+    return taskLockbox;
+  }
+
+  public MergerDBCoordinator getMergerDBCoordinator()
+  {
+    return mergerDBCoordinator;
+  }
+
+  public ServiceEmitter getEmitter()
+  {
+    return emitter;
+  }
+
+  public boolean taskLockCoversSegments(
+      final Task task,
+      final Set<DataSegment> segments,
+      final boolean allowOlderVersions
+  )
+  {
+    // Verify that each of these segments falls under some lock
+
+    // NOTE: It is possible for our lock to be revoked (if the task has failed and given up its locks) after we check
+    // NOTE: it and before we perform the segment insert, but, that should be OK since the worst that happens is we
+    // NOTE: insert some segments from the task but not others.
+
+    final List<TaskLock> taskLocks = getTaskLockbox().findLocksForTask(task);
+    for(final DataSegment segment : segments) {
+      final boolean ok = Iterables.any(
+          taskLocks, new Predicate<TaskLock>()
+      {
+        @Override
+        public boolean apply(TaskLock taskLock)
+        {
+          final boolean versionOk = allowOlderVersions
+                                    ? taskLock.getVersion().compareTo(segment.getVersion()) >= 0
+                                    : taskLock.getVersion().equals(segment.getVersion());
+
+          return versionOk
+                 && taskLock.getDataSource().equals(segment.getDataSource())
+                 && taskLock.getInterval().contains(segment.getInterval());
+        }
+      }
+      );
+
+      if (!ok) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/config/TaskConfig.java

@@ -0,0 +1,21 @@
+package com.metamx.druid.merger.common.config;
+
+import com.metamx.druid.merger.common.task.Task;
+import org.skife.config.Config;
+import org.skife.config.Default;
+
+import java.io.File;
+
+public abstract class TaskConfig
+{
+  @Config("druid.merger.taskDir")
+  public abstract File getBaseTaskDir();
+
+  @Config("druid.merger.rowFlushBoundary")
+  @Default("500000")
+  public abstract int getDefaultRowFlushBoundary();
+
+  public File getTaskDir(final Task task) {
+    return new File(getBaseTaskDir(), task.getId());
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/index/YeOldePlumberSchool.java

@@ -35,7 +35,7 @@ import com.metamx.druid.client.DataSegment;
 import com.metamx.druid.index.QueryableIndex;
 import com.metamx.druid.index.v1.IndexIO;
 import com.metamx.druid.index.v1.IndexMerger;
-import com.metamx.druid.loading.SegmentPusher;
+import com.metamx.druid.loading.DataSegmentPusher;
 import com.metamx.druid.query.QueryRunner;
 import com.metamx.druid.realtime.FireDepartmentMetrics;
 import com.metamx.druid.realtime.FireHydrant;
@@ -45,11 +45,11 @@ import com.metamx.druid.realtime.Schema;
 import com.metamx.druid.realtime.Sink;
 
 
-
-
+import org.apache.commons.io.FileUtils;
 import org.joda.time.Interval;
 
 import java.io.File;
+import java.io.IOException;
 import java.util.List;
 import java.util.Set;
 
@@ -61,7 +61,7 @@ public class YeOldePlumberSchool implements PlumberSchool
 {
   private final Interval interval;
   private final String version;
-  private final SegmentPusher segmentPusher;
+  private final DataSegmentPusher dataSegmentPusher;
   private final File tmpSegmentDir;
 
   private static final Logger log = new Logger(YeOldePlumberSchool.class);
@@ -70,13 +70,13 @@ public class YeOldePlumberSchool implements PlumberSchool
   public YeOldePlumberSchool(
       @JsonProperty("interval") Interval interval,
       @JsonProperty("version") String version,
-      @JacksonInject("segmentPusher") SegmentPusher segmentPusher,
+      @JacksonInject("segmentPusher") DataSegmentPusher dataSegmentPusher,
       @JacksonInject("tmpSegmentDir") File tmpSegmentDir
   )
   {
     this.interval = interval;
     this.version = version;
-    this.segmentPusher = segmentPusher;
+    this.dataSegmentPusher = dataSegmentPusher;
     this.tmpSegmentDir = tmpSegmentDir;
   }
 
@@ -120,13 +120,13 @@ public class YeOldePlumberSchool implements PlumberSchool
       @Override
       public void finishJob()
       {
+        // The segment we will upload
+        File fileToUpload = null;
+
         try {
           // User should have persisted everything by now.
           Preconditions.checkState(!theSink.swappable(), "All data must be persisted before fininshing the job!");
 
-          // The segment we will upload
-          final File fileToUpload;
-
           if(spilled.size() == 0) {
             throw new IllegalStateException("Nothing indexed?");
           } else if(spilled.size() == 1) {
@@ -149,7 +149,7 @@ public class YeOldePlumberSchool implements PlumberSchool
                                                      .withVersion(version)
                                                      .withBinaryVersion(IndexIO.getVersionFromDir(fileToUpload));
 
-          segmentPusher.push(fileToUpload, segmentToUpload);
+          dataSegmentPusher.push(fileToUpload, segmentToUpload);
 
           log.info(
               "Uploaded segment[%s]",
@@ -160,6 +160,17 @@ public class YeOldePlumberSchool implements PlumberSchool
           log.warn(e, "Failed to merge and upload");
           throw Throwables.propagate(e);
         }
+        finally {
+          try {
+            if (fileToUpload != null) {
+              log.info("Deleting Index File[%s]", fileToUpload);
+              FileUtils.deleteDirectory(fileToUpload);
+            }
+          }
+          catch (IOException e) {
+            log.warn(e, "Error deleting directory[%s]", fileToUpload);
+          }
+        }
       }
 
       private void spillIfSwappable()

merger/src/main/java/com/metamx/druid/merger/common/task/AbstractTask.java

@@ -22,11 +22,10 @@ package com.metamx.druid.merger.common.task;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.common.base.Objects;
+import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.metamx.druid.merger.common.TaskStatus;
-import com.metamx.druid.merger.coordinator.TaskContext;
-
-
+import com.metamx.druid.merger.common.TaskToolbox;
 import org.joda.time.Interval;
 
 public abstract class AbstractTask implements Task
@@ -34,30 +33,19 @@ public abstract class AbstractTask implements Task
   private final String id;
   private final String groupId;
   private final String dataSource;
-  private final Interval interval;
+  private final Optional<Interval> interval;
 
-  public AbstractTask(String id, String dataSource, Interval interval)
+  protected AbstractTask(String id, String dataSource, Interval interval)
   {
     this(id, id, dataSource, interval);
   }
 
-  @JsonCreator
-  public AbstractTask(
-      @JsonProperty("id") String id,
-      @JsonProperty("groupId") String groupId,
-      @JsonProperty("dataSource") String dataSource,
-      @JsonProperty("interval") Interval interval
-  )
+  protected AbstractTask(String id, String groupId, String dataSource, Interval interval)
   {
-    Preconditions.checkNotNull(id, "id");
-    Preconditions.checkNotNull(groupId, "groupId");
-    Preconditions.checkNotNull(dataSource, "dataSource");
-    Preconditions.checkNotNull(interval, "interval");
-
-    this.id = id;
-    this.groupId = groupId;
-    this.dataSource = dataSource;
-    this.interval = interval;
+    this.id = Preconditions.checkNotNull(id, "id");
+    this.groupId = Preconditions.checkNotNull(groupId, "groupId");
+    this.dataSource = Preconditions.checkNotNull(dataSource, "dataSource");
+    this.interval = Optional.fromNullable(interval);
   }
 
   @JsonProperty
@@ -81,15 +69,15 @@ public abstract class AbstractTask implements Task
     return dataSource;
   }
 
-  @JsonProperty
+  @JsonProperty("interval")
   @Override
-  public Interval getInterval()
+  public Optional<Interval> getFixedInterval()
   {
     return interval;
   }
 
   @Override
-  public TaskStatus preflight(TaskContext context) throws Exception
+  public TaskStatus preflight(TaskToolbox toolbox) throws Exception
   {
     return TaskStatus.running(id);
   }
@@ -101,7 +89,7 @@ public abstract class AbstractTask implements Task
                   .add("id", id)
                   .add("type", getType())
                   .add("dataSource", dataSource)
-                  .add("interval", getInterval())
+                  .add("interval", getFixedInterval())
                   .toString();
   }
 }

merger/src/main/java/com/metamx/druid/merger/common/task/AppendTask.java

@@ -62,7 +62,7 @@ public class AppendTask extends MergeTask
       throws Exception
   {
     VersionedIntervalTimeline<String, DataSegment> timeline = new VersionedIntervalTimeline<String, DataSegment>(
-        Ordering.natural().nullsFirst()
+        Ordering.<String>natural().nullsFirst()
     );
 
     for (DataSegment segment : segments.keySet()) {
@@ -111,9 +111,9 @@ public class AppendTask extends MergeTask
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    return Task.Type.APPEND;
+    return "append";
   }
 
   private class SegmentToMergeHolder

merger/src/main/java/com/metamx/druid/merger/common/task/DefaultMergeTask.java

@@ -82,8 +82,8 @@ public class DefaultMergeTask extends MergeTask
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    return Task.Type.MERGE;
+    return "merge";
   }
 }

merger/src/main/java/com/metamx/druid/merger/common/task/DeleteTask.java

@@ -21,6 +21,9 @@ package com.metamx.druid.merger.common.task;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
 import com.metamx.common.logger.Logger;
 import com.metamx.druid.QueryGranularity;
@@ -30,19 +33,16 @@ import com.metamx.druid.index.v1.IncrementalIndex;
 import com.metamx.druid.index.v1.IncrementalIndexAdapter;
 import com.metamx.druid.index.v1.IndexMerger;
 import com.metamx.druid.index.v1.IndexableAdapter;
-import com.metamx.druid.jackson.DefaultObjectMapper;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
-import com.metamx.druid.merger.coordinator.TaskContext;
+import com.metamx.druid.merger.common.actions.LockListAction;
+import com.metamx.druid.merger.common.actions.SegmentInsertAction;
 import com.metamx.druid.shard.NoneShardSpec;
-
-
-
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
 import java.io.File;
-import java.util.ArrayList;
 
 public class DeleteTask extends AbstractTask
 {
@@ -63,29 +63,31 @@ public class DeleteTask extends AbstractTask
             new DateTime().toString()
         ),
         dataSource,
-        interval
+        Preconditions.checkNotNull(interval, "interval")
     );
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    return Task.Type.DELETE;
+    return "delete";
   }
 
   @Override
-  public TaskStatus run(TaskContext context, TaskToolbox toolbox) throws Exception
+  public TaskStatus run(TaskToolbox toolbox) throws Exception
   {
     // Strategy: Create an empty segment covering the interval to be deleted
+    final TaskLock myLock = Iterables.getOnlyElement(toolbox.getTaskActionClient().submit(new LockListAction(this)));
+    final Interval interval = this.getFixedInterval().get();
     final IncrementalIndex empty = new IncrementalIndex(0, QueryGranularity.NONE, new AggregatorFactory[0]);
-    final IndexableAdapter emptyAdapter = new IncrementalIndexAdapter(this.getInterval(), empty);
+    final IndexableAdapter emptyAdapter = new IncrementalIndexAdapter(interval, empty);
 
     // Create DataSegment
     final DataSegment segment =
         DataSegment.builder()
                    .dataSource(this.getDataSource())
-                   .interval(this.getInterval())
-                   .version(context.getVersion())
+                   .interval(interval)
+                   .version(myLock.getVersion())
                    .shardSpec(new NoneShardSpec())
                    .build();
 
@@ -102,6 +104,8 @@ public class DeleteTask extends AbstractTask
         segment.getVersion()
     );
 
-    return TaskStatus.success(getId(), Lists.newArrayList(uploadedSegment));
+    toolbox.getTaskActionClient().submit(new SegmentInsertAction(this, ImmutableSet.of(uploadedSegment)));
+
+    return TaskStatus.success(getId());
   }
 }

merger/src/main/java/com/metamx/druid/merger/common/task/IndexDeterminePartitionsTask.java

@@ -22,7 +22,7 @@ package com.metamx.druid.merger.common.task;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.common.base.Function;
-import com.google.common.collect.Iterables;
+import com.google.common.base.Preconditions;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Maps;
 import com.google.common.collect.Ordering;
@@ -33,18 +33,15 @@ import com.metamx.common.logger.Logger;
 import com.metamx.druid.input.InputRow;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
-import com.metamx.druid.merger.coordinator.TaskContext;
+import com.metamx.druid.merger.common.actions.SpawnTasksAction;
 import com.metamx.druid.realtime.Firehose;
 import com.metamx.druid.realtime.FirehoseFactory;
 import com.metamx.druid.realtime.Schema;
 import com.metamx.druid.shard.NoneShardSpec;
 import com.metamx.druid.shard.ShardSpec;
 import com.metamx.druid.shard.SingleDimensionShardSpec;
-
-
 import org.joda.time.Interval;
 
-import javax.annotation.Nullable;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -53,8 +50,15 @@ public class IndexDeterminePartitionsTask extends AbstractTask
 {
   @JsonProperty
   private final FirehoseFactory firehoseFactory;
-  @JsonProperty private final Schema schema;
-  @JsonProperty private final long targetPartitionSize;
+
+  @JsonProperty
+  private final Schema schema;
+
+  @JsonProperty
+  private final long targetPartitionSize;
+
+  @JsonProperty
+  private final int rowFlushBoundary;
 
   private static final Logger log = new Logger(IndexTask.class);
 
@@ -64,7 +68,8 @@ public class IndexDeterminePartitionsTask extends AbstractTask
       @JsonProperty("interval") Interval interval,
       @JsonProperty("firehose") FirehoseFactory firehoseFactory,
       @JsonProperty("schema") Schema schema,
-      @JsonProperty("targetPartitionSize") long targetPartitionSize
+      @JsonProperty("targetPartitionSize") long targetPartitionSize,
+      @JsonProperty("rowFlushBoundary") int rowFlushBoundary
   )
   {
     super(
@@ -76,30 +81,30 @@ public class IndexDeterminePartitionsTask extends AbstractTask
         ),
         groupId,
         schema.getDataSource(),
-        interval
+        Preconditions.checkNotNull(interval, "interval")
     );
 
     this.firehoseFactory = firehoseFactory;
     this.schema = schema;
     this.targetPartitionSize = targetPartitionSize;
+    this.rowFlushBoundary = rowFlushBoundary;
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    return Type.INDEX;
+    return "index_partitions";
   }
 
   @Override
-  public TaskStatus run(TaskContext context, TaskToolbox toolbox) throws Exception
+  public TaskStatus run(TaskToolbox toolbox) throws Exception
   {
     log.info("Running with targetPartitionSize[%d]", targetPartitionSize);
 
-    // This is similar to what DeterminePartitionsJob does in the hadoop indexer, but we don't require
-    // a preconfigured partition dimension (we'll just pick the one with highest cardinality).
+    // TODO: Replace/merge/whatever with hadoop determine-partitions code
 
-    // XXX - Space-efficiency (stores all unique dimension values, although at least not all combinations)
-    // XXX - Time-efficiency (runs all this on one single node instead of through map/reduce)
+    // We know this exists
+    final Interval interval = getFixedInterval().get();
 
     // Blacklist dimensions that have multiple values per row
     final Set<String> unusableDimensions = Sets.newHashSet();
@@ -111,24 +116,24 @@ public class IndexDeterminePartitionsTask extends AbstractTask
     final Firehose firehose = firehoseFactory.connect();
 
     try {
-      while(firehose.hasMore()) {
+      while (firehose.hasMore()) {
 
         final InputRow inputRow = firehose.nextRow();
 
-        if(getInterval().contains(inputRow.getTimestampFromEpoch())) {
+        if (interval.contains(inputRow.getTimestampFromEpoch())) {
 
           // Extract dimensions from event
           for (final String dim : inputRow.getDimensions()) {
             final List<String> dimValues = inputRow.getDimension(dim);
 
-            if(!unusableDimensions.contains(dim)) {
+            if (!unusableDimensions.contains(dim)) {
 
-              if(dimValues.size() == 1) {
+              if (dimValues.size() == 1) {
 
                 // Track this value
                 TreeMultiset<String> dimensionValueMultiset = dimensionValueMultisets.get(dim);
 
-                if(dimensionValueMultiset == null) {
+                if (dimensionValueMultiset == null) {
                   dimensionValueMultiset = TreeMultiset.create();
                   dimensionValueMultisets.put(dim, dimensionValueMultiset);
                 }
@@ -149,7 +154,8 @@ public class IndexDeterminePartitionsTask extends AbstractTask
         }
 
       }
-    } finally {
+    }
+    finally {
       firehose.close();
     }
 
@@ -169,7 +175,7 @@ public class IndexDeterminePartitionsTask extends AbstractTask
       }
     };
 
-    if(dimensionValueMultisets.isEmpty()) {
+    if (dimensionValueMultisets.isEmpty()) {
       // No suitable partition dimension. We'll make one big segment and hope for the best.
       log.info("No suitable partition dimension found");
       shardSpecs.add(new NoneShardSpec());
@@ -191,9 +197,9 @@ public class IndexDeterminePartitionsTask extends AbstractTask
       // Iterate over unique partition dimension values in sorted order
       String currentPartitionStart = null;
       int currentPartitionSize = 0;
-      for(final String partitionDimValue : partitionDimValues.elementSet()) {
+      for (final String partitionDimValue : partitionDimValues.elementSet()) {
         currentPartitionSize += partitionDimValues.count(partitionDimValue);
-        if(currentPartitionSize >= targetPartitionSize) {
+        if (currentPartitionSize >= targetPartitionSize) {
           final ShardSpec shardSpec = new SingleDimensionShardSpec(
               partitionDim,
               currentPartitionStart,
@@ -229,28 +235,31 @@ public class IndexDeterminePartitionsTask extends AbstractTask
       }
     }
 
-    return TaskStatus.continued(
-        getId(),
-        Lists.transform(
-            shardSpecs, new Function<ShardSpec, Task>()
+    List<Task> nextTasks = Lists.transform(
+        shardSpecs,
+        new Function<ShardSpec, Task>()
         {
           @Override
           public Task apply(ShardSpec shardSpec)
           {
             return new IndexGeneratorTask(
                 getGroupId(),
-                getInterval(),
+                getFixedInterval().get(),
                 firehoseFactory,
                 new Schema(
                     schema.getDataSource(),
                     schema.getAggregators(),
                     schema.getIndexGranularity(),
                     shardSpec
-                )
+                ),
+                rowFlushBoundary
             );
           }
         }
-        )
     );
+
+    toolbox.getTaskActionClient().submit(new SpawnTasksAction(this, nextTasks));
+
+    return TaskStatus.success(getId());
   }
 }

merger/src/main/java/com/metamx/druid/merger/common/task/IndexGeneratorTask.java

@@ -21,25 +21,26 @@ package com.metamx.druid.merger.common.task;
 
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonProperty;
-import com.google.common.collect.ImmutableList;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import com.metamx.common.logger.Logger;
 import com.metamx.druid.client.DataSegment;
 import com.metamx.druid.input.InputRow;
+import com.metamx.druid.loading.DataSegmentPusher;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
+import com.metamx.druid.merger.common.actions.LockListAction;
+import com.metamx.druid.merger.common.actions.SegmentInsertAction;
 import com.metamx.druid.merger.common.index.YeOldePlumberSchool;
-import com.metamx.druid.merger.coordinator.TaskContext;
 import com.metamx.druid.realtime.FireDepartmentMetrics;
 import com.metamx.druid.realtime.Firehose;
 import com.metamx.druid.realtime.FirehoseFactory;
 import com.metamx.druid.realtime.Plumber;
 import com.metamx.druid.realtime.Schema;
-import com.metamx.druid.loading.SegmentPusher;
 import com.metamx.druid.realtime.Sink;
-
-
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
@@ -57,6 +58,9 @@ public class IndexGeneratorTask extends AbstractTask
   @JsonProperty
   private final Schema schema;
 
+  @JsonProperty
+  private final int rowFlushBoundary;
+
   private static final Logger log = new Logger(IndexTask.class);
 
   @JsonCreator
@@ -64,7 +68,8 @@ public class IndexGeneratorTask extends AbstractTask
       @JsonProperty("groupId") String groupId,
       @JsonProperty("interval") Interval interval,
       @JsonProperty("firehose") FirehoseFactory firehoseFactory,
-      @JsonProperty("schema") Schema schema
+      @JsonProperty("schema") Schema schema,
+      @JsonProperty("rowFlushBoundary") int rowFlushBoundary
   )
   {
     super(
@@ -77,22 +82,29 @@ public class IndexGeneratorTask extends AbstractTask
         ),
         groupId,
         schema.getDataSource(),
-        interval
+        Preconditions.checkNotNull(interval, "interval")
     );
 
     this.firehoseFactory = firehoseFactory;
     this.schema = schema;
+    this.rowFlushBoundary = rowFlushBoundary;
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    return Type.INDEX;
+    return "index_generator";
   }
 
   @Override
-  public TaskStatus run(final TaskContext context, final TaskToolbox toolbox) throws Exception
+  public TaskStatus run(final TaskToolbox toolbox) throws Exception
   {
+    // We should have a lock from before we started running
+    final TaskLock myLock = Iterables.getOnlyElement(toolbox.getTaskActionClient().submit(new LockListAction(this)));
+
+    // We know this exists
+    final Interval interval = getFixedInterval().get();
+
     // Set up temporary directory for indexing
     final File tmpDir = new File(
         String.format(
@@ -101,9 +113,9 @@ public class IndexGeneratorTask extends AbstractTask
             String.format(
                 "%s_%s_%s_%s_%s",
                 this.getDataSource(),
-                this.getInterval().getStart(),
-                this.getInterval().getEnd(),
-                context.getVersion(),
+                interval.getStart(),
+                interval.getEnd(),
+                myLock.getVersion(),
                 schema.getShardSpec().getPartitionNum()
             )
         )
@@ -111,7 +123,7 @@ public class IndexGeneratorTask extends AbstractTask
 
     // We need to track published segments.
     final List<DataSegment> pushedSegments = new CopyOnWriteArrayList<DataSegment>();
-    final SegmentPusher wrappedSegmentPusher = new SegmentPusher()
+    final DataSegmentPusher wrappedDataSegmentPusher = new DataSegmentPusher()
     {
       @Override
       public DataSegment push(File file, DataSegment segment) throws IOException
@@ -126,12 +138,17 @@ public class IndexGeneratorTask extends AbstractTask
     final FireDepartmentMetrics metrics = new FireDepartmentMetrics();
     final Firehose firehose = firehoseFactory.connect();
     final Plumber plumber = new YeOldePlumberSchool(
-        getInterval(),
-        context.getVersion(),
-        wrappedSegmentPusher,
+        interval,
+        myLock.getVersion(),
+        wrappedDataSegmentPusher,
         tmpDir
     ).findPlumber(schema, metrics);
 
+    // rowFlushBoundary for this job
+    final int myRowFlushBoundary = this.rowFlushBoundary > 0
+                                   ? rowFlushBoundary
+                                   : toolbox.getConfig().getDefaultRowFlushBoundary();
+
     try {
       while(firehose.hasMore()) {
         final InputRow inputRow = firehose.nextRow();
@@ -150,7 +167,7 @@ public class IndexGeneratorTask extends AbstractTask
           int numRows = sink.add(inputRow);
           metrics.incrementProcessed();
 
-          if(numRows >= toolbox.getConfig().getRowFlushBoundary()) {
+          if(numRows >= myRowFlushBoundary) {
             plumber.persist(firehose.commit());
           }
         } else {
@@ -175,8 +192,11 @@ public class IndexGeneratorTask extends AbstractTask
         metrics.rowOutput()
     );
 
+    // Request segment pushes
+    toolbox.getTaskActionClient().submit(new SegmentInsertAction(this, ImmutableSet.copyOf(pushedSegments)));
+
     // Done
-    return TaskStatus.success(getId(), ImmutableList.copyOf(pushedSegments));
+    return TaskStatus.success(getId());
   }
 
   /**
@@ -185,7 +205,7 @@ public class IndexGeneratorTask extends AbstractTask
    * @return true or false
    */
   private boolean shouldIndex(InputRow inputRow) {
-    if(!getInterval().contains(inputRow.getTimestampFromEpoch())) {
+    if(!getFixedInterval().get().contains(inputRow.getTimestampFromEpoch())) {
       return false;
     }
 

merger/src/main/java/com/metamx/druid/merger/common/task/IndexTask.java

@@ -29,7 +29,7 @@ import com.metamx.druid.aggregation.AggregatorFactory;
 import com.metamx.druid.indexer.granularity.GranularitySpec;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
-import com.metamx.druid.merger.coordinator.TaskContext;
+import com.metamx.druid.merger.common.actions.SpawnTasksAction;
 import com.metamx.druid.realtime.FirehoseFactory;
 import com.metamx.druid.realtime.Schema;
 import com.metamx.druid.shard.NoneShardSpec;
@@ -42,11 +42,23 @@ import java.util.List;
 
 public class IndexTask extends AbstractTask
 {
-  @JsonProperty private final GranularitySpec granularitySpec;
-  @JsonProperty private final AggregatorFactory[] aggregators;
-  @JsonProperty private final QueryGranularity indexGranularity;
-  @JsonProperty private final long targetPartitionSize;
-  @JsonProperty private final FirehoseFactory firehoseFactory;
+  @JsonProperty
+  private final GranularitySpec granularitySpec;
+
+  @JsonProperty
+  private final AggregatorFactory[] aggregators;
+
+  @JsonProperty
+  private final QueryGranularity indexGranularity;
+
+  @JsonProperty
+  private final long targetPartitionSize;
+
+  @JsonProperty
+  private final FirehoseFactory firehoseFactory;
+
+  @JsonProperty
+  private final int rowFlushBoundary;
 
   private static final Logger log = new Logger(IndexTask.class);
 
@@ -57,7 +69,8 @@ public class IndexTask extends AbstractTask
       @JsonProperty("aggregators") AggregatorFactory[] aggregators,
       @JsonProperty("indexGranularity") QueryGranularity indexGranularity,
       @JsonProperty("targetPartitionSize") long targetPartitionSize,
-      @JsonProperty("firehose") FirehoseFactory firehoseFactory
+      @JsonProperty("firehose") FirehoseFactory firehoseFactory,
+      @JsonProperty("rowFlushBoundary") int rowFlushBoundary
   )
   {
     super(
@@ -75,6 +88,7 @@ public class IndexTask extends AbstractTask
     this.indexGranularity = indexGranularity;
     this.targetPartitionSize = targetPartitionSize;
     this.firehoseFactory = firehoseFactory;
+    this.rowFlushBoundary = rowFlushBoundary;
   }
 
   public List<Task> toSubtasks()
@@ -95,7 +109,8 @@ public class IndexTask extends AbstractTask
                     indexGranularity,
                     new NoneShardSpec()
                 ),
-                targetPartitionSize
+                targetPartitionSize,
+                rowFlushBoundary
             )
         );
       } else {
@@ -110,7 +125,8 @@ public class IndexTask extends AbstractTask
                     aggregators,
                     indexGranularity,
                     new NoneShardSpec()
-                )
+                ),
+                rowFlushBoundary
             )
         );
       }
@@ -120,19 +136,20 @@ public class IndexTask extends AbstractTask
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    return Type.INDEX;
+    return "index";
   }
 
   @Override
-  public TaskStatus preflight(TaskContext context) throws Exception
+  public TaskStatus preflight(TaskToolbox toolbox) throws Exception
   {
-    return TaskStatus.continued(getId(), toSubtasks());
+    toolbox.getTaskActionClient().submit(new SpawnTasksAction(this, toSubtasks()));
+    return TaskStatus.success(getId());
   }
 
   @Override
-  public TaskStatus run(TaskContext context, TaskToolbox toolbox) throws Exception
+  public TaskStatus run(TaskToolbox toolbox) throws Exception
   {
     throw new IllegalStateException("IndexTasks should not be run!");
   }

merger/src/main/java/com/metamx/druid/merger/common/task/KillTask.java

@@ -0,0 +1,98 @@
+package com.metamx.druid.merger.common.task;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Iterables;
+import com.metamx.common.ISE;
+import com.metamx.common.logger.Logger;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.TaskToolbox;
+import com.metamx.druid.merger.common.actions.LockListAction;
+import com.metamx.druid.merger.common.actions.SegmentListUnusedAction;
+import com.metamx.druid.merger.common.actions.SegmentNukeAction;
+import com.metamx.druid.merger.common.TaskLock;
+import com.fasterxml.jackson.annotation.JsonCreator;
+import com.fasterxml.jackson.annotation.JsonProperty;
+import org.joda.time.DateTime;
+import org.joda.time.Interval;
+
+import java.util.List;
+
+/**
+ */
+public class KillTask extends AbstractTask
+{
+  private static final Logger log = new Logger(KillTask.class);
+
+  @JsonCreator
+  public KillTask(
+      @JsonProperty("dataSource") String dataSource,
+      @JsonProperty("interval") Interval interval
+  )
+  {
+    super(
+        String.format(
+            "kill_%s_%s_%s_%s",
+            dataSource,
+            interval.getStart(),
+            interval.getEnd(),
+            new DateTime().toString()
+        ),
+        dataSource,
+        interval
+    );
+  }
+
+  @Override
+  public String getType()
+  {
+    return "kill";
+  }
+
+  @Override
+  public TaskStatus run(TaskToolbox toolbox) throws Exception
+  {
+    // Confirm we have a lock (will throw if there isn't exactly one element)
+    final TaskLock myLock = Iterables.getOnlyElement(toolbox.getTaskActionClient().submit(new LockListAction(this)));
+
+    if(!myLock.getDataSource().equals(getDataSource())) {
+      throw new ISE("WTF?! Lock dataSource[%s] != task dataSource[%s]", myLock.getDataSource(), getDataSource());
+    }
+
+    if(!myLock.getInterval().equals(getFixedInterval().get())) {
+      throw new ISE("WTF?! Lock interval[%s] != task interval[%s]", myLock.getInterval(), getFixedInterval().get());
+    }
+
+    // List unused segments
+    final List<DataSegment> unusedSegments = toolbox.getTaskActionClient()
+                                                    .submit(
+                                                        new SegmentListUnusedAction(
+                                                            this,
+                                                            myLock.getDataSource(),
+                                                            myLock.getInterval()
+                                                        )
+                                                    );
+
+    // Verify none of these segments have versions > lock version
+    for(final DataSegment unusedSegment : unusedSegments) {
+      if(unusedSegment.getVersion().compareTo(myLock.getVersion()) > 0) {
+        throw new ISE(
+            "WTF?! Unused segment[%s] has version[%s] > task version[%s]",
+            unusedSegment.getIdentifier(),
+            unusedSegment.getVersion(),
+            myLock.getVersion()
+        );
+      }
+
+      log.info("OK to kill segment: %s", unusedSegment.getIdentifier());
+    }
+
+    // Kill segments
+    toolbox.getSegmentKiller().kill(unusedSegments);
+
+    // Remove metadata for these segments
+    toolbox.getTaskActionClient().submit(new SegmentNukeAction(this, ImmutableSet.copyOf(unusedSegments)));
+
+    return TaskStatus.success(getId());
+  }
+}

merger/src/main/java/com/metamx/druid/merger/common/task/MergeTask.java

@@ -22,6 +22,7 @@ package com.metamx.druid.merger.common.task;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.google.common.base.Charsets;
 import com.google.common.base.Function;
 import com.google.common.base.Joiner;
 import com.google.common.base.Objects;
@@ -31,24 +32,22 @@ import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
-import com.google.common.collect.Maps;
 import com.google.common.collect.Ordering;
 import com.google.common.collect.Sets;
+import com.google.common.hash.Hashing;
 import com.metamx.common.ISE;
 import com.metamx.common.logger.Logger;
 import com.metamx.druid.client.DataSegment;
-import com.metamx.druid.loading.SegmentPuller;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
-import com.metamx.druid.merger.coordinator.TaskContext;
+import com.metamx.druid.merger.common.actions.LockListAction;
+import com.metamx.druid.merger.common.actions.SegmentInsertAction;
+import com.metamx.druid.merger.common.actions.SegmentListUsedAction;
 import com.metamx.druid.shard.NoneShardSpec;
 import com.metamx.emitter.service.AlertEvent;
 import com.metamx.emitter.service.ServiceEmitter;
 import com.metamx.emitter.service.ServiceMetricEvent;
-import org.apache.commons.codec.digest.DigestUtils;
-
-
-
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
@@ -118,11 +117,12 @@ public abstract class MergeTask extends AbstractTask
   }
 
   @Override
-  public TaskStatus run(TaskContext context, TaskToolbox toolbox) throws Exception
+  public TaskStatus run(TaskToolbox toolbox) throws Exception
   {
+    final TaskLock myLock = Iterables.getOnlyElement(toolbox.getTaskActionClient().submit(new LockListAction(this)));
     final ServiceEmitter emitter = toolbox.getEmitter();
     final ServiceMetricEvent.Builder builder = new ServiceMetricEvent.Builder();
-    final DataSegment mergedSegment = computeMergedSegment(getDataSource(), context.getVersion(), segments);
+    final DataSegment mergedSegment = computeMergedSegment(getDataSource(), myLock.getVersion(), segments);
     final File taskDir = toolbox.getConfig().getTaskDir(this);
 
     try {
@@ -147,13 +147,7 @@ public abstract class MergeTask extends AbstractTask
 
 
       // download segments to merge
-      final Map<String, SegmentPuller> segmentGetters = toolbox.getSegmentGetters(this);
-      final Map<DataSegment, File> gettedSegments = Maps.newHashMap();
-      for (final DataSegment segment : segments) {
-        Map<String, Object> loadSpec = segment.getLoadSpec();
-        SegmentPuller segmentPuller = segmentGetters.get(loadSpec.get("type"));
-        gettedSegments.put(segment, segmentPuller.getSegmentFiles(segment));
-      }
+      final Map<DataSegment, File> gettedSegments = toolbox.getSegments(this, segments);
 
       // merge files together
       final File fileToUpload = merge(gettedSegments, new File(taskDir, "merged"));
@@ -176,7 +170,9 @@ public abstract class MergeTask extends AbstractTask
       emitter.emit(builder.build("merger/uploadTime", System.currentTimeMillis() - uploadStart));
       emitter.emit(builder.build("merger/mergeSize", uploadedSegment.getSize()));
 
-      return TaskStatus.success(getId(), Lists.newArrayList(uploadedSegment));
+      toolbox.getTaskActionClient().submit(new SegmentInsertAction(this, ImmutableSet.of(uploadedSegment)));
+
+      return TaskStatus.success(getId());
     }
     catch (Exception e) {
       log.error(
@@ -205,7 +201,7 @@ public abstract class MergeTask extends AbstractTask
    * we are operating on every segment that overlaps the chosen interval.
    */
   @Override
-  public TaskStatus preflight(TaskContext context)
+  public TaskStatus preflight(TaskToolbox toolbox)
   {
     final Function<DataSegment, String> toIdentifier = new Function<DataSegment, String>()
     {
@@ -216,7 +212,13 @@ public abstract class MergeTask extends AbstractTask
       }
     };
 
-    final Set<String> current = ImmutableSet.copyOf(Iterables.transform(context.getCurrentSegments(), toIdentifier));
+    final Set<String> current = ImmutableSet.copyOf(
+        Iterables.transform(
+            toolbox.getTaskActionClient()
+                   .submit(new SegmentListUsedAction(this, getDataSource(), getFixedInterval().get())),
+            toIdentifier
+        )
+    );
     final Set<String> requested = ImmutableSet.copyOf(Iterables.transform(segments, toIdentifier));
 
     final Set<String> missingFromRequested = Sets.difference(current, requested);
@@ -254,7 +256,7 @@ public abstract class MergeTask extends AbstractTask
     return Objects.toStringHelper(this)
                   .add("id", getId())
                   .add("dataSource", getDataSource())
-                  .add("interval", getInterval())
+                  .add("interval", getFixedInterval())
                   .add("segments", segments)
                   .toString();
   }
@@ -280,7 +282,11 @@ public abstract class MergeTask extends AbstractTask
         )
     );
 
-    return String.format("%s_%s", dataSource, DigestUtils.shaHex(segmentIDs).toLowerCase());
+    return String.format(
+        "%s_%s",
+        dataSource,
+        Hashing.sha1().hashString(segmentIDs, Charsets.UTF_8).toString().toLowerCase()
+    );
   }
 
   private static Interval computeMergedInterval(final List<DataSegment> segments)

merger/src/main/java/com/metamx/druid/merger/common/task/Task.java

@@ -21,15 +21,9 @@ package com.metamx.druid.merger.common.task;
 
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
+import com.google.common.base.Optional;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
-import com.metamx.druid.merger.coordinator.TaskContext;
-import com.metamx.druid.merger.common.task.IndexDeterminePartitionsTask;
-import com.metamx.druid.merger.common.task.IndexGeneratorTask;
-import com.metamx.druid.merger.common.task.IndexTask;
-
-
-import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
 /**
@@ -38,53 +32,66 @@ import org.joda.time.Interval;
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, property = "type", defaultImpl = DefaultMergeTask.class)
 @JsonSubTypes(value = {
     @JsonSubTypes.Type(name = "append", value = AppendTask.class),
+    @JsonSubTypes.Type(name = "merge", value = DefaultMergeTask.class),
     @JsonSubTypes.Type(name = "delete", value = DeleteTask.class),
+    @JsonSubTypes.Type(name = "kill", value = KillTask.class),
     @JsonSubTypes.Type(name = "index", value = IndexTask.class),
     @JsonSubTypes.Type(name = "index_partitions", value = IndexDeterminePartitionsTask.class),
     @JsonSubTypes.Type(name = "index_generator", value = IndexGeneratorTask.class)
 })
 public interface Task
 {
-  enum Type
-  {
-    INDEX,
-    MERGE,
-    APPEND,
-    DELETE,
-    TEST
-  }
-
+  /**
+   * Returns ID of this task. Must be unique across all tasks ever created.
+   */
   public String getId();
 
+  /**
+   * Returns group ID of this task. Tasks with the same group ID can share locks. If tasks do not need to share locks,
+   * a common convention is to set group ID equal to task ID.
+   */
   public String getGroupId();
 
-  public Type getType();
+  /**
+   * Returns a descriptive label for this task type. Used for metrics emission and logging.
+   */
+  public String getType();
 
+  /**
+   * Returns the datasource this task operates on. Each task can operate on only one datasource.
+   */
   public String getDataSource();
 
-  public Interval getInterval();
+  /**
+   * Returns fixed interval for this task, if any. Tasks without fixed intervals are not granted locks when started
+   * and must explicitly request them.
+   */
+  public Optional<Interval> getFixedInterval();
 
   /**
    * Execute preflight checks for a task. This typically runs on the coordinator, and will be run while
    * holding a lock on our dataSource and interval. If this method throws an exception, the task should be
    * considered a failure.
    *
-   * @param context Context for this task, gathered under indexer lock
+   * @param toolbox Toolbox for this task
+   *
    * @return Some kind of status (runnable means continue on to a worker, non-runnable means we completed without
-   * using a worker).
+   *         using a worker).
+   *
    * @throws Exception
    */
-  public TaskStatus preflight(TaskContext context) throws Exception;
+  public TaskStatus preflight(TaskToolbox toolbox) throws Exception;
 
   /**
    * Execute a task. This typically runs on a worker as determined by a TaskRunner, and will be run while
    * holding a lock on our dataSource and interval. If this method throws an exception, the task should be
    * considered a failure.
    *
-   * @param context Context for this task, gathered under indexer lock
    * @param toolbox Toolbox for this task
+   *
    * @return Some kind of finished status (isRunnable must be false).
+   *
    * @throws Exception
    */
-  public TaskStatus run(TaskContext context, TaskToolbox toolbox) throws Exception;
+  public TaskStatus run(TaskToolbox toolbox) throws Exception;
 }

merger/src/main/java/com/metamx/druid/merger/common/task/V8toV9UpgradeTask.java

@@ -3,8 +3,6 @@ package com.metamx.druid.merger.common.task;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
-import com.metamx.druid.merger.coordinator.TaskContext;
-
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 
@@ -25,15 +23,13 @@ public class V8toV9UpgradeTask extends AbstractTask
   }
 
   @Override
-  public Type getType()
+  public String getType()
   {
-    throw new UnsupportedOperationException("Do we really need to return a Type?");
+    return "8to9";
   }
 
   @Override
-  public TaskStatus run(
-      TaskContext context, TaskToolbox toolbox
-  ) throws Exception
+  public TaskStatus run(TaskToolbox toolbox) throws Exception
   {
     throw new UnsupportedOperationException();
   }

merger/src/main/java/com/metamx/druid/merger/coordinator/DbTaskStorage.java

@@ -24,18 +24,25 @@ import com.google.common.base.Function;
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
 import com.google.common.base.Throwables;
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
 import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.metamx.common.Pair;
 import com.metamx.common.logger.Logger;
 import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.actions.TaskAction;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.task.Task;
 import com.metamx.druid.merger.coordinator.config.IndexerDbConnectorConfig;
 
 import org.joda.time.DateTime;
 import org.skife.jdbi.v2.DBI;
 import org.skife.jdbi.v2.Handle;
+import org.skife.jdbi.v2.exceptions.StatementException;
 import org.skife.jdbi.v2.tweak.HandleCallback;
 
+import javax.annotation.Nullable;
 import java.util.List;
 import java.util.Map;
 
@@ -68,44 +75,46 @@ public class DbTaskStorage implements TaskStorage
 
     log.info("Inserting task %s with status: %s", task.getId(), status);
 
-    dbi.withHandle(
-        new HandleCallback<Void>()
-        {
-          @Override
-          public Void withHandle(Handle handle) throws Exception
+    try {
+      dbi.withHandle(
+          new HandleCallback<Void>()
           {
-            handle.createStatement(
-                String.format(
-                    "INSERT INTO %s (id, created_date, payload, status_code, status_payload) VALUES (:id, :created_date, :payload, :status_code, :status_payload)",
-                    dbConnectorConfig.getTaskTable()
-                )
-            )
-                  .bind("id", task.getId())
-                  .bind("created_date", new DateTime().toString())
-                  .bind("payload", jsonMapper.writeValueAsString(task))
-                  .bind("status_code", status.getStatusCode().toString())
-                  .bind("status_payload", jsonMapper.writeValueAsString(status))
-                  .execute();
+            @Override
+            public Void withHandle(Handle handle) throws Exception
+            {
+              handle.createStatement(
+                  String.format(
+                      "INSERT INTO %s (id, created_date, payload, status_code, status_payload) VALUES (:id, :created_date, :payload, :status_code, :status_payload)",
+                      dbConnectorConfig.getTaskTable()
+                  )
+              )
+                    .bind("id", task.getId())
+                    .bind("created_date", new DateTime().toString())
+                    .bind("payload", jsonMapper.writeValueAsString(task))
+                    .bind("status_code", status.getStatusCode().toString())
+                    .bind("status_payload", jsonMapper.writeValueAsString(status))
+                    .execute();
 
-            return null;
+              return null;
+            }
           }
-        }
-    );
+      );
+    } catch (StatementException e) {
+      // Might be a duplicate task ID.
+      if(getTask(task.getId()).isPresent()) {
+        throw new TaskExistsException(task.getId(), e);
+      } else {
+        throw e;
+      }
+    }
   }
 
   @Override
-  public void setStatus(final String taskid, final TaskStatus status)
+  public void setStatus(final TaskStatus status)
   {
-    Preconditions.checkNotNull(taskid, "task");
     Preconditions.checkNotNull(status, "status");
-    Preconditions.checkArgument(
-        taskid.equals(status.getId()),
-        "Task/Status ID mismatch[%s/%s]",
-        taskid,
-        status.getId()
-    );
 
-    log.info("Updating task %s to status: %s", taskid, status);
+    log.info("Updating task %s to status: %s", status.getId(), status);
 
     int updated = dbi.withHandle(
         new HandleCallback<Integer>()
@@ -115,12 +124,13 @@ public class DbTaskStorage implements TaskStorage
           {
             return handle.createStatement(
                 String.format(
-                    "UPDATE %s SET status_code = :status_code, status_payload = :status_payload WHERE id = :id",
+                    "UPDATE %s SET status_code = :status_code, status_payload = :status_payload WHERE id = :id AND status_code = :old_status_code",
                     dbConnectorConfig.getTaskTable()
                 )
             )
-                  .bind("id", taskid)
+                  .bind("id", status.getId())
                   .bind("status_code", status.getStatusCode().toString())
+                  .bind("old_status_code", TaskStatus.Status.RUNNING.toString())
                   .bind("status_payload", jsonMapper.writeValueAsString(status))
                   .execute();
           }
@@ -128,35 +138,35 @@ public class DbTaskStorage implements TaskStorage
     );
 
     if(updated != 1) {
-      throw new IllegalStateException(String.format("Task not found: %s", taskid));
+      throw new IllegalStateException(String.format("Running task not found: %s", status.getId()));
     }
   }
 
   @Override
-  public void setVersion(final String taskid, final String version)
+  public Optional<Task> getTask(final String taskid)
   {
-    Preconditions.checkNotNull(taskid, "task");
-    Preconditions.checkNotNull(version, "version");
-
-    log.info("Updating task %s to version: %s", taskid, version);
-
-    dbi.withHandle(
-        new HandleCallback<Void>()
+    return dbi.withHandle(
+        new HandleCallback<Optional<Task>>()
         {
           @Override
-          public Void withHandle(Handle handle) throws Exception
+          public Optional<Task> withHandle(Handle handle) throws Exception
           {
-            handle.createStatement(
-                String.format(
-                    "UPDATE %s SET version = :version WHERE id = :id",
-                    dbConnectorConfig.getTaskTable()
+            final List<Map<String, Object>> dbTasks =
+                handle.createQuery(
+                    String.format(
+                        "SELECT payload FROM %s WHERE id = :id",
+                        dbConnectorConfig.getTaskTable()
+                    )
                 )
-            )
-                  .bind("id", taskid)
-                  .bind("version", version)
-                  .execute();
+                      .bind("id", taskid)
+                      .list();
 
-            return null;
+            if(dbTasks.size() == 0) {
+              return Optional.absent();
+            } else {
+              final Map<String, Object> dbStatus = Iterables.getOnlyElement(dbTasks);
+              return Optional.of(jsonMapper.readValue(dbStatus.get("payload").toString(), Task.class));
+            }
           }
         }
     );
@@ -192,36 +202,6 @@ public class DbTaskStorage implements TaskStorage
     );
   }
 
-  @Override
-  public Optional<String> getVersion(final String taskid)
-  {
-    return dbi.withHandle(
-        new HandleCallback<Optional<String>>()
-        {
-          @Override
-          public Optional<String> withHandle(Handle handle) throws Exception
-          {
-            final List<Map<String, Object>> dbStatuses =
-                handle.createQuery(
-                    String.format(
-                        "SELECT version FROM %s WHERE id = :id",
-                        dbConnectorConfig.getTaskTable()
-                    )
-                )
-                      .bind("id", taskid)
-                      .list();
-
-            if(dbStatuses.size() == 0) {
-              return Optional.absent();
-            } else {
-              final Map<String, Object> dbStatus = Iterables.getOnlyElement(dbStatuses);
-              return Optional.fromNullable((String) dbStatus.get("version"));
-            }
-          }
-        }
-    );
-  }
-
   @Override
   public List<Task> getRunningTasks()
   {
@@ -259,4 +239,183 @@ public class DbTaskStorage implements TaskStorage
         }
     );
   }
+
+  @Override
+  public void addLock(final String taskid, final TaskLock taskLock)
+  {
+    Preconditions.checkNotNull(taskid, "taskid");
+    Preconditions.checkNotNull(taskLock, "taskLock");
+
+    log.info(
+        "Adding lock on interval[%s] version[%s] for task: %s",
+        taskLock.getInterval(),
+        taskLock.getVersion(),
+        taskid
+    );
+
+    dbi.withHandle(
+        new HandleCallback<Integer>()
+        {
+          @Override
+          public Integer withHandle(Handle handle) throws Exception
+          {
+            return handle.createStatement(
+                String.format(
+                    "INSERT INTO %s (task_id, lock_payload) VALUES (:task_id, :lock_payload)",
+                    dbConnectorConfig.getTaskLockTable()
+                )
+            )
+                         .bind("task_id", taskid)
+                         .bind("lock_payload", jsonMapper.writeValueAsString(taskLock))
+                         .execute();
+          }
+        }
+    );
+  }
+
+  @Override
+  public void removeLock(String taskid, TaskLock taskLockToRemove)
+  {
+    Preconditions.checkNotNull(taskid, "taskid");
+    Preconditions.checkNotNull(taskLockToRemove, "taskLockToRemove");
+
+    final Map<Long, TaskLock> taskLocks = getLocksWithIds(taskid);
+
+    for(final Map.Entry<Long, TaskLock> taskLockWithId : taskLocks.entrySet()) {
+      final long id = taskLockWithId.getKey();
+      final TaskLock taskLock = taskLockWithId.getValue();
+
+      if(taskLock.equals(taskLockToRemove)) {
+        log.info("Deleting TaskLock with id[%d]: %s", id, taskLock);
+
+        dbi.withHandle(
+            new HandleCallback<Integer>()
+            {
+              @Override
+              public Integer withHandle(Handle handle) throws Exception
+              {
+                return handle.createStatement(
+                    String.format(
+                        "DELETE FROM %s WHERE id = :id",
+                        dbConnectorConfig.getTaskLockTable()
+                    )
+                )
+                             .bind("id", id)
+                             .execute();
+              }
+            }
+        );
+      }
+    }
+  }
+
+  @Override
+  public List<TaskLock> getLocks(String taskid)
+  {
+    return ImmutableList.copyOf(
+        Iterables.transform(
+            getLocksWithIds(taskid).entrySet(), new Function<Map.Entry<Long, TaskLock>, TaskLock>()
+        {
+          @Override
+          public TaskLock apply(Map.Entry<Long, TaskLock> e)
+          {
+            return e.getValue();
+          }
+        }
+        )
+    );
+  }
+
+  @Override
+  public <T> void addAuditLog(final TaskAction<T> taskAction)
+  {
+    Preconditions.checkNotNull(taskAction, "taskAction");
+
+    log.info("Logging action for task[%s]: %s", taskAction.getTask().getId(), taskAction);
+
+    dbi.withHandle(
+        new HandleCallback<Integer>()
+        {
+          @Override
+          public Integer withHandle(Handle handle) throws Exception
+          {
+            return handle.createStatement(
+                String.format(
+                    "INSERT INTO %s (task_id, log_payload) VALUES (:task_id, :log_payload)",
+                    dbConnectorConfig.getTaskLogTable()
+                )
+            )
+                         .bind("task_id", taskAction.getTask().getId())
+                         .bind("log_payload", jsonMapper.writeValueAsString(taskAction))
+                         .execute();
+          }
+        }
+    );
+  }
+
+  @Override
+  public List<TaskAction> getAuditLogs(final String taskid)
+  {
+    return dbi.withHandle(
+        new HandleCallback<List<TaskAction>>()
+        {
+          @Override
+          public List<TaskAction> withHandle(Handle handle) throws Exception
+          {
+            final List<Map<String, Object>> dbTaskLogs =
+                handle.createQuery(
+                    String.format(
+                        "SELECT log_payload FROM %s WHERE task_id = :task_id",
+                        dbConnectorConfig.getTaskLogTable()
+                    )
+                )
+                      .bind("task_id", taskid)
+                      .list();
+
+            return Lists.transform(
+                dbTaskLogs, new Function<Map<String, Object>, TaskAction>()
+            {
+              @Override
+              public TaskAction apply(Map<String, Object> row)
+              {
+                try {
+                  return jsonMapper.readValue(row.get("payload").toString(), TaskAction.class);
+                } catch(Exception e) {
+                  throw Throwables.propagate(e);
+                }
+              }
+            }
+            );
+          }
+        }
+    );
+  }
+
+  private Map<Long, TaskLock> getLocksWithIds(final String taskid)
+  {
+    return dbi.withHandle(
+        new HandleCallback<Map<Long, TaskLock>>()
+        {
+          @Override
+          public Map<Long, TaskLock> withHandle(Handle handle) throws Exception
+          {
+            final List<Map<String, Object>> dbTaskLocks =
+                handle.createQuery(
+                    String.format(
+                        "SELECT id, lock_payload FROM %s WHERE task_id = :task_id",
+                        dbConnectorConfig.getTaskLockTable()
+                    )
+                )
+                      .bind("task_id", taskid)
+                      .list();
+
+            final Map<Long, TaskLock> retMap = Maps.newHashMap();
+            for(final Map<String, Object> row : dbTaskLocks) {
+              retMap.put((Long)row.get("id"), jsonMapper.readValue(row.get("lock_payload").toString(), TaskLock.class));
+            }
+            return retMap;
+          }
+        }
+    );
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/LocalTaskRunner.java

@@ -20,14 +20,17 @@
 package com.metamx.druid.merger.coordinator;
 
 import com.google.common.base.Throwables;
+import com.google.common.collect.Lists;
 import com.metamx.common.lifecycle.LifecycleStop;
 import com.metamx.common.logger.Logger;
+import com.metamx.druid.merger.common.TaskCallback;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.TaskToolbox;
 import com.metamx.druid.merger.common.task.Task;
 import org.apache.commons.io.FileUtils;
 
 import java.io.File;
+import java.util.Collection;
 import java.util.concurrent.ExecutorService;
 
 /**
@@ -38,7 +41,7 @@ public class LocalTaskRunner implements TaskRunner
   private final TaskToolbox toolbox;
   private final ExecutorService exec;
 
-  private static final Logger log = new Logger(TaskQueue.class);
+  private static final Logger log = new Logger(LocalTaskRunner.class);
 
   public LocalTaskRunner(
       TaskToolbox toolbox,
@@ -56,7 +59,7 @@ public class LocalTaskRunner implements TaskRunner
   }
 
   @Override
-  public void run(final Task task, final TaskContext context, final TaskCallback callback)
+  public void run(final Task task, final TaskCallback callback)
   {
     exec.submit(
         new Runnable()
@@ -65,12 +68,12 @@ public class LocalTaskRunner implements TaskRunner
           public void run()
           {
             final long startTime = System.currentTimeMillis();
-            final File taskDir = toolbox.getConfig().getTaskDir(task);
 
             TaskStatus status;
 
             try {
-              status = task.run(context, toolbox);
+              log.info("Running task: %s", task.getId());
+              status = task.run(toolbox);
             }
             catch (InterruptedException e) {
               log.error(e, "Interrupted while running task[%s]", task);
@@ -86,23 +89,43 @@ public class LocalTaskRunner implements TaskRunner
             }
 
             try {
+              final File taskDir = toolbox.getConfig().getTaskDir(task);
+
               if (taskDir.exists()) {
                 log.info("Removing task directory: %s", taskDir);
                 FileUtils.deleteDirectory(taskDir);
               }
             }
             catch (Exception e) {
-              log.error(e, "Failed to delete task directory[%s]", taskDir.toString());
+              log.error(e, "Failed to delete task directory: %s", task.getId());
             }
 
             try {
               callback.notify(status.withDuration(System.currentTimeMillis() - startTime));
-            } catch(Throwable t) {
-              log.error(t, "Uncaught Throwable during callback for task[%s]", task);
-              throw Throwables.propagate(t);
+            } catch(Exception e) {
+              log.error(e, "Uncaught Exception during callback for task[%s]", task);
+              throw Throwables.propagate(e);
             }
           }
         }
     );
   }
+
+  @Override
+  public Collection<TaskRunnerWorkItem> getRunningTasks()
+  {
+    return Lists.newArrayList();
+  }
+
+  @Override
+  public Collection<TaskRunnerWorkItem> getPendingTasks()
+  {
+    return Lists.newArrayList();
+  }
+
+  @Override
+  public Collection<ZkWorker> getWorkers()
+  {
+    return Lists.newArrayList();
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/LocalTaskStorage.java

@@ -21,17 +21,20 @@ package com.metamx.druid.merger.coordinator;
 
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
-import com.google.common.base.Predicate;
+import com.google.common.collect.ArrayListMultimap;
+import com.google.common.collect.HashMultimap;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
+import com.google.common.collect.Multimap;
 import com.metamx.common.logger.Logger;
 import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.actions.TaskAction;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.task.Task;
 
-import javax.annotation.Nullable;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * Implements an in-heap TaskStorage facility, with no persistence across restarts. This class is not
@@ -39,93 +42,178 @@ import java.util.Map;
  */
 public class LocalTaskStorage implements TaskStorage
 {
+  private final ReentrantLock giant = new ReentrantLock();
   private final Map<String, TaskStuff> tasks = Maps.newHashMap();
+  private final Multimap<String, TaskLock> taskLocks = HashMultimap.create();
+  private final Multimap<String, TaskAction> taskActions = ArrayListMultimap.create();
 
   private static final Logger log = new Logger(LocalTaskStorage.class);
 
   @Override
   public void insert(Task task, TaskStatus status)
   {
-    Preconditions.checkNotNull(task, "task");
-    Preconditions.checkNotNull(status, "status");
-    Preconditions.checkArgument(
-        task.getId().equals(status.getId()),
-        "Task/Status ID mismatch[%s/%s]",
-        task.getId(),
-        status.getId()
-    );
-    Preconditions.checkState(!tasks.containsKey(task.getId()), "Task ID must not already be present: %s", task.getId());
-    log.info("Inserting task %s with status: %s", task.getId(), status);
-    tasks.put(task.getId(), new TaskStuff(task, status));
+    giant.lock();
+
+    try {
+      Preconditions.checkNotNull(task, "task");
+      Preconditions.checkNotNull(status, "status");
+      Preconditions.checkArgument(
+          task.getId().equals(status.getId()),
+          "Task/Status ID mismatch[%s/%s]",
+          task.getId(),
+          status.getId()
+      );
+
+      if(tasks.containsKey(task.getId())) {
+        throw new TaskExistsException(task.getId());
+      }
+
+      log.info("Inserting task %s with status: %s", task.getId(), status);
+      tasks.put(task.getId(), new TaskStuff(task, status));
+    } finally {
+      giant.unlock();
+    }
   }
 
   @Override
-  public void setStatus(String taskid, TaskStatus status)
+  public Optional<Task> getTask(String taskid)
   {
-    Preconditions.checkNotNull(taskid, "taskid");
-    Preconditions.checkNotNull(status, "status");
-    Preconditions.checkState(tasks.containsKey(taskid), "Task ID must already be present: %s", taskid);
-    log.info("Updating task %s to status: %s", taskid, status);
-    tasks.put(taskid, tasks.get(taskid).withStatus(status));
+    giant.lock();
+
+    try {
+      Preconditions.checkNotNull(taskid, "taskid");
+      if(tasks.containsKey(taskid)) {
+        return Optional.of(tasks.get(taskid).getTask());
+      } else {
+        return Optional.absent();
+      }
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  @Override
+  public void setStatus(TaskStatus status)
+  {
+    giant.lock();
+
+    try {
+      Preconditions.checkNotNull(status, "status");
+
+      final String taskid = status.getId();
+      Preconditions.checkState(tasks.containsKey(taskid), "Task ID must already be present: %s", taskid);
+      Preconditions.checkState(tasks.get(taskid).getStatus().isRunnable(), "Task status must be runnable: %s", taskid);
+      log.info("Updating task %s to status: %s", taskid, status);
+      tasks.put(taskid, tasks.get(taskid).withStatus(status));
+    } finally {
+      giant.unlock();
+    }
   }
 
   @Override
   public Optional<TaskStatus> getStatus(String taskid)
   {
-    Preconditions.checkNotNull(taskid, "taskid");
-    if(tasks.containsKey(taskid)) {
-      return Optional.of(tasks.get(taskid).status);
-    } else {
-      return Optional.absent();
-    }
-  }
+    giant.lock();
 
-  @Override
-  public void setVersion(String taskid, String version)
-  {
-    Preconditions.checkNotNull(taskid, "taskid");
-    Preconditions.checkNotNull(version, "status");
-    Preconditions.checkState(tasks.containsKey(taskid), "Task ID must already be present: %s", taskid);
-    log.info("Updating task %s to version: %s", taskid, version);
-    tasks.put(taskid, tasks.get(taskid).withVersion(version));
-  }
-
-  @Override
-  public Optional<String> getVersion(String taskid)
-  {
-    Preconditions.checkNotNull(taskid, "taskid");
-    if(tasks.containsKey(taskid)) {
-      return tasks.get(taskid).version;
-    } else {
-      return Optional.absent();
+    try {
+      Preconditions.checkNotNull(taskid, "taskid");
+      if(tasks.containsKey(taskid)) {
+        return Optional.of(tasks.get(taskid).getStatus());
+      } else {
+        return Optional.absent();
+      }
+    } finally {
+      giant.unlock();
     }
   }
 
   @Override
   public List<Task> getRunningTasks()
   {
-    final ImmutableList.Builder<Task> listBuilder = ImmutableList.builder();
-    for(final TaskStuff taskStuff : tasks.values()) {
-      if(taskStuff.status.isRunnable()) {
-        listBuilder.add(taskStuff.task);
-      }
-    }
+    giant.lock();
 
-    return listBuilder.build();
+    try {
+      final ImmutableList.Builder<Task> listBuilder = ImmutableList.builder();
+      for(final TaskStuff taskStuff : tasks.values()) {
+        if(taskStuff.getStatus().isRunnable()) {
+          listBuilder.add(taskStuff.getTask());
+        }
+      }
+
+      return listBuilder.build();
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  @Override
+  public void addLock(final String taskid, final TaskLock taskLock)
+  {
+    giant.lock();
+
+    try {
+      Preconditions.checkNotNull(taskLock, "taskLock");
+      taskLocks.put(taskid, taskLock);
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  @Override
+  public void removeLock(final String taskid, final TaskLock taskLock)
+  {
+    giant.lock();
+
+    try {
+      Preconditions.checkNotNull(taskLock, "taskLock");
+      taskLocks.remove(taskid, taskLock);
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  @Override
+  public List<TaskLock> getLocks(final String taskid)
+  {
+    giant.lock();
+
+    try {
+      return ImmutableList.copyOf(taskLocks.get(taskid));
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  @Override
+  public <T> void addAuditLog(TaskAction<T> taskAction)
+  {
+    giant.lock();
+
+    try {
+      taskActions.put(taskAction.getTask().getId(), taskAction);
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  @Override
+  public List<TaskAction> getAuditLogs(String taskid)
+  {
+    giant.lock();
+
+    try {
+      return ImmutableList.copyOf(taskActions.get(taskid));
+    } finally {
+      giant.unlock();
+    }
   }
 
   private static class TaskStuff
   {
     final Task task;
     final TaskStatus status;
-    final Optional<String> version;
 
     private TaskStuff(Task task, TaskStatus status)
-    {
-      this(task, status, Optional.<String>absent());
-    }
-
-    private TaskStuff(Task task, TaskStatus status, Optional<String> version)
     {
       Preconditions.checkNotNull(task);
       Preconditions.checkNotNull(status);
@@ -133,17 +221,21 @@ public class LocalTaskStorage implements TaskStorage
 
       this.task = task;
       this.status = status;
-      this.version = version;
+    }
+
+    public Task getTask()
+    {
+      return task;
+    }
+
+    public TaskStatus getStatus()
+    {
+      return status;
     }
 
     private TaskStuff withStatus(TaskStatus _status)
     {
-      return new TaskStuff(task, _status, version);
-    }
-
-    private TaskStuff withVersion(String _version)
-    {
-      return new TaskStuff(task, status, Optional.of(_version));
+      return new TaskStuff(task, _status);
     }
   }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/MergerDBCoordinator.java

@@ -21,6 +21,7 @@ package com.metamx.druid.merger.coordinator;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Function;
+import com.google.common.base.Throwables;
 import com.google.common.collect.Lists;
 import com.google.common.collect.Ordering;
 import com.metamx.common.logger.Logger;
@@ -28,18 +29,23 @@ import com.metamx.druid.TimelineObjectHolder;
 import com.metamx.druid.VersionedIntervalTimeline;
 import com.metamx.druid.client.DataSegment;
 import com.metamx.druid.db.DbConnectorConfig;
-
 import org.joda.time.DateTime;
 import org.joda.time.Interval;
 import org.skife.jdbi.v2.DBI;
+import org.skife.jdbi.v2.FoldController;
+import org.skife.jdbi.v2.Folder3;
 import org.skife.jdbi.v2.Handle;
 import org.skife.jdbi.v2.ResultIterator;
+import org.skife.jdbi.v2.StatementContext;
+import org.skife.jdbi.v2.TransactionCallback;
+import org.skife.jdbi.v2.TransactionStatus;
 import org.skife.jdbi.v2.tweak.HandleCallback;
 
-import javax.annotation.Nullable;
 import java.io.IOException;
+import java.sql.SQLException;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 /**
  */
@@ -47,8 +53,6 @@ public class MergerDBCoordinator
 {
   private static final Logger log = new Logger(MergerDBCoordinator.class);
 
-  private final Object lock = new Object();
-
   private final ObjectMapper jsonMapper;
   private final DbConnectorConfig dbConnectorConfig;
   private final DBI dbi;
@@ -64,132 +68,205 @@ public class MergerDBCoordinator
     this.dbi = dbi;
   }
 
-  public List<DataSegment> getSegmentsForInterval(final String dataSource, final Interval interval) throws IOException
+  public List<DataSegment> getUsedSegmentsForInterval(final String dataSource, final Interval interval)
+      throws IOException
   {
-    synchronized (lock) {
+    // XXX Could be reading from a cache if we can assume we're the only one editing the DB
 
-      // XXX Could be reading from a cache if we can assume we're the only one editing the DB
-
-      final VersionedIntervalTimeline<String, DataSegment> timeline = dbi.withHandle(
-          new HandleCallback<VersionedIntervalTimeline<String, DataSegment>>()
+    final VersionedIntervalTimeline<String, DataSegment> timeline = dbi.withHandle(
+        new HandleCallback<VersionedIntervalTimeline<String, DataSegment>>()
+        {
+          @Override
+          public VersionedIntervalTimeline<String, DataSegment> withHandle(Handle handle) throws Exception
           {
-            @Override
-            public VersionedIntervalTimeline<String, DataSegment> withHandle(Handle handle) throws Exception
-            {
-              final VersionedIntervalTimeline<String, DataSegment> timeline = new VersionedIntervalTimeline<String, DataSegment>(
-                  Ordering.natural()
-              );
+            final VersionedIntervalTimeline<String, DataSegment> timeline = new VersionedIntervalTimeline<String, DataSegment>(
+                Ordering.natural()
+            );
 
-              final ResultIterator<Map<String, Object>> dbSegments =
-                  handle.createQuery(
-                      String.format(
-                          "SELECT payload FROM %s WHERE used = 1 AND dataSource = :dataSource",
-                          dbConnectorConfig.getSegmentTable()
-                      )
-                  )
-                        .bind("dataSource", dataSource)
-                        .iterator();
-
-              while (dbSegments.hasNext()) {
-
-                final Map<String, Object> dbSegment = dbSegments.next();
-
-                DataSegment segment = jsonMapper.readValue(
-                    (String) dbSegment.get("payload"),
-                    DataSegment.class
-                );
-
-                timeline.add(segment.getInterval(), segment.getVersion(), segment.getShardSpec().createChunk(segment));
-
-              }
-
-              dbSegments.close();
-
-              return timeline;
-
-            }
-          }
-      );
-
-      final List<DataSegment> segments = Lists.transform(
-          timeline.lookup(interval),
-          new Function<TimelineObjectHolder<String, DataSegment>, DataSegment>()
-          {
-            @Override
-            public DataSegment apply(@Nullable TimelineObjectHolder<String, DataSegment> input)
-            {
-              return input.getObject().getChunk(0).getObject();
-            }
-          }
-      );
-
-      return segments;
-
-    }
-  }
-
-  public void announceHistoricalSegment(final DataSegment segment) throws Exception
-  {
-    synchronized (lock) {
-      try {
-        List<Map<String, Object>> exists = dbi.withHandle(
-            new HandleCallback<List<Map<String, Object>>>()
-            {
-              @Override
-              public List<Map<String, Object>> withHandle(Handle handle) throws Exception
-              {
-                return handle.createQuery(
+            final ResultIterator<Map<String, Object>> dbSegments =
+                handle.createQuery(
                     String.format(
-                        "SELECT id FROM %s WHERE id = ':identifier'",
-                        dbConnectorConfig.getSegmentTable()
-                    )
-                ).bind(
-                    "identifier",
-                    segment.getIdentifier()
-                ).list();
-              }
-            }
-        );
-
-        if (!exists.isEmpty()) {
-          log.info("Found [%s] in DB, not updating DB", segment.getIdentifier());
-          return;
-        }
-
-        dbi.withHandle(
-            new HandleCallback<Void>()
-            {
-              @Override
-              public Void withHandle(Handle handle) throws Exception
-              {
-                handle.createStatement(
-                    String.format(
-                        "INSERT INTO %s (id, dataSource, created_date, start, end, partitioned, version, used, payload) VALUES (:id, :dataSource, :created_date, :start, :end, :partitioned, :version, :used, :payload)",
+                        "SELECT payload FROM %s WHERE used = 1 AND dataSource = :dataSource",
                         dbConnectorConfig.getSegmentTable()
                     )
                 )
-                      .bind("id", segment.getIdentifier())
-                      .bind("dataSource", segment.getDataSource())
-                      .bind("created_date", new DateTime().toString())
-                      .bind("start", segment.getInterval().getStart().toString())
-                      .bind("end", segment.getInterval().getEnd().toString())
-                      .bind("partitioned", segment.getShardSpec().getPartitionNum())
-                      .bind("version", segment.getVersion())
-                      .bind("used", true)
-                      .bind("payload", jsonMapper.writeValueAsString(segment))
-                      .execute();
+                      .bind("dataSource", dataSource)
+                      .iterator();
+
+            while (dbSegments.hasNext()) {
+
+              final Map<String, Object> dbSegment = dbSegments.next();
+
+              DataSegment segment = jsonMapper.readValue(
+                  (String) dbSegment.get("payload"),
+                  DataSegment.class
+              );
+
+              timeline.add(segment.getInterval(), segment.getVersion(), segment.getShardSpec().createChunk(segment));
 
-                return null;
-              }
             }
-        );
 
-        log.info("Published segment [%s] to DB", segment.getIdentifier());
-      }
-      catch (Exception e) {
-        log.error(e, "Exception inserting into DB");
-        throw new RuntimeException(e);
+            dbSegments.close();
+
+            return timeline;
+
+          }
+        }
+    );
+
+    final List<DataSegment> segments = Lists.transform(
+        timeline.lookup(interval),
+        new Function<TimelineObjectHolder<String, DataSegment>, DataSegment>()
+        {
+          @Override
+          public DataSegment apply(TimelineObjectHolder<String, DataSegment> input)
+          {
+            return input.getObject().getChunk(0).getObject();
+          }
+        }
+    );
+
+    return segments;
+  }
+
+  public void announceHistoricalSegments(final Set<DataSegment> segments) throws Exception
+  {
+    dbi.inTransaction(
+        new TransactionCallback<Void>()
+        {
+          @Override
+          public Void inTransaction(Handle handle, TransactionStatus transactionStatus) throws Exception
+          {
+            for(final DataSegment segment : segments) {
+              announceHistoricalSegment(handle, segment);
+            }
+
+            return null;
+          }
+        }
+    );
+  }
+
+
+  private void announceHistoricalSegment(final Handle handle, final DataSegment segment) throws Exception
+  {
+    try {
+      final List<Map<String, Object>> exists = handle.createQuery(
+          String.format(
+              "SELECT id FROM %s WHERE id = ':identifier'",
+              dbConnectorConfig.getSegmentTable()
+          )
+      ).bind(
+          "identifier",
+          segment.getIdentifier()
+      ).list();
+
+      if (!exists.isEmpty()) {
+        log.info("Found [%s] in DB, not updating DB", segment.getIdentifier());
+        return;
       }
+
+      handle.createStatement(
+          String.format(
+              "INSERT INTO %s (id, dataSource, created_date, start, end, partitioned, version, used, payload) VALUES (:id, :dataSource, :created_date, :start, :end, :partitioned, :version, :used, :payload)",
+              dbConnectorConfig.getSegmentTable()
+          )
+      )
+            .bind("id", segment.getIdentifier())
+            .bind("dataSource", segment.getDataSource())
+            .bind("created_date", new DateTime().toString())
+            .bind("start", segment.getInterval().getStart().toString())
+            .bind("end", segment.getInterval().getEnd().toString())
+            .bind("partitioned", segment.getShardSpec().getPartitionNum())
+            .bind("version", segment.getVersion())
+            .bind("used", true)
+            .bind("payload", jsonMapper.writeValueAsString(segment))
+            .execute();
+
+      log.info("Published segment [%s] to DB", segment.getIdentifier());
+    }
+    catch (Exception e) {
+      log.error(e, "Exception inserting into DB");
+      throw e;
     }
   }
+
+  public void deleteSegments(final Set<DataSegment> segments) throws Exception
+  {
+    dbi.inTransaction(
+        new TransactionCallback<Void>()
+        {
+          @Override
+          public Void inTransaction(Handle handle, TransactionStatus transactionStatus) throws Exception
+          {
+            for(final DataSegment segment : segments) {
+              deleteSegment(handle, segment);
+            }
+
+            return null;
+          }
+        }
+    );
+  }
+
+  private void deleteSegment(final Handle handle, final DataSegment segment)
+  {
+    handle.createStatement(
+        String.format("DELETE from %s WHERE id = :id", dbConnectorConfig.getSegmentTable())
+    ).bind("id", segment.getIdentifier())
+          .execute();
+  }
+
+  public List<DataSegment> getUnusedSegmentsForInterval(final String dataSource, final Interval interval)
+  {
+    List<DataSegment> matchingSegments = dbi.withHandle(
+        new HandleCallback<List<DataSegment>>()
+        {
+          @Override
+          public List<DataSegment> withHandle(Handle handle) throws Exception
+          {
+            return handle.createQuery(
+                String.format(
+                    "SELECT payload FROM %s WHERE dataSource = :dataSource and start >= :start and end <= :end and used = 0",
+                    dbConnectorConfig.getSegmentTable()
+                )
+            )
+                         .bind("dataSource", dataSource)
+                         .bind("start", interval.getStart().toString())
+                         .bind("end", interval.getEnd().toString())
+                         .fold(
+                             Lists.<DataSegment>newArrayList(),
+                             new Folder3<List<DataSegment>, Map<String, Object>>()
+                             {
+                               @Override
+                               public List<DataSegment> fold(
+                                   List<DataSegment> accumulator,
+                                   Map<String, Object> stringObjectMap,
+                                   FoldController foldController,
+                                   StatementContext statementContext
+                               ) throws SQLException
+                               {
+                                 try {
+                                   DataSegment segment = jsonMapper.readValue(
+                                       (String) stringObjectMap.get("payload"),
+                                       DataSegment.class
+                                   );
+
+                                   accumulator.add(segment);
+
+                                   return accumulator;
+                                 }
+                                 catch (Exception e) {
+                                   throw Throwables.propagate(e);
+                                 }
+                               }
+                             }
+                         );
+          }
+        }
+    );
+
+    log.info("Found %,d segments for %s for interval %s.", matchingSegments.size(), dataSource, interval);
+    return matchingSegments;
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/RemoteTaskRunner.java

@@ -20,7 +20,6 @@
 package com.metamx.druid.merger.coordinator;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
-import com.google.common.base.Function;
 import com.google.common.base.Joiner;
 import com.google.common.base.Predicate;
 import com.google.common.base.Throwables;
@@ -29,17 +28,13 @@ import com.google.common.collect.MinMaxPriorityQueue;
 import com.google.common.collect.Sets;
 import com.google.common.primitives.Ints;
 import com.metamx.common.ISE;
-import com.metamx.common.concurrent.ScheduledExecutors;
 import com.metamx.common.guava.FunctionalIterable;
 import com.metamx.common.lifecycle.LifecycleStart;
 import com.metamx.common.lifecycle.LifecycleStop;
-import com.metamx.druid.PeriodGranularity;
-import com.metamx.druid.merger.common.TaskHolder;
+import com.metamx.druid.merger.common.TaskCallback;
 import com.metamx.druid.merger.common.TaskStatus;
 import com.metamx.druid.merger.common.task.Task;
 import com.metamx.druid.merger.coordinator.config.RemoteTaskRunnerConfig;
-import com.metamx.druid.merger.coordinator.scaling.AutoScalingData;
-import com.metamx.druid.merger.coordinator.scaling.ScalingStrategy;
 import com.metamx.druid.merger.coordinator.setup.WorkerSetupManager;
 import com.metamx.druid.merger.worker.Worker;
 import com.metamx.emitter.EmittingLogger;
@@ -49,31 +44,31 @@ import com.netflix.curator.framework.recipes.cache.PathChildrenCacheEvent;
 import com.netflix.curator.framework.recipes.cache.PathChildrenCacheListener;
 import com.netflix.curator.utils.ZKPaths;
 import org.apache.zookeeper.CreateMode;
-
 import org.joda.time.DateTime;
-import org.joda.time.Duration;
-import org.joda.time.Period;
 
-import java.util.Arrays;
+import java.util.Collection;
 import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentHashMap;
-import java.util.concurrent.ConcurrentSkipListSet;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
 /**
- * The RemoteTaskRunner encapsulates all interactions with Zookeeper and keeps track of which workers
- * are running which tasks. The RemoteTaskRunner is event driven and updates state according to ephemeral node
- * changes in ZK.
+ * The RemoteTaskRunner's primary responsibility is to assign tasks to worker nodes and manage retries in failure
+ * scenarios. The RemoteTaskRunner keeps track of which workers are running which tasks and manages coordinator and
+ * worker interactions over Zookeeper. The RemoteTaskRunner is event driven and updates state according to ephemeral
+ * node changes in ZK.
  * <p/>
- * The RemoteTaskRunner will assign tasks to a node until the node hits capacity. RemoteTaskRunners have scaling
- * strategies to help them decide when to create or delete new resources. When tasks are assigned to the remote
- * task runner and no workers have capacity to handle the task, provisioning will be done according to the strategy.
- * The remote task runner periodically runs a check to see if any worker nodes have not had any work for a
- * specified period of time. If so, the worker node will be terminated.
+ * The RemoteTaskRunner will assign tasks to a node until the node hits capacity. At that point, task assignment will
+ * fail. The RemoteTaskRunner depends on another component to create additional worker resources.
+ * For example, {@link com.metamx.druid.merger.coordinator.scaling.ResourceManagementScheduler} can take care of these duties.
  * <p/>
  * If a worker node becomes inexplicably disconnected from Zk, the RemoteTaskRunner will automatically retry any tasks
  * that were associated with the node.
@@ -89,20 +84,19 @@ public class RemoteTaskRunner implements TaskRunner
   private final PathChildrenCache workerPathCache;
   private final ScheduledExecutorService scheduledExec;
   private final RetryPolicyFactory retryPolicyFactory;
-  private final ScalingStrategy strategy;
   private final WorkerSetupManager workerSetupManager;
 
   // all workers that exist in ZK
-  private final Map<String, WorkerWrapper> zkWorkers = new ConcurrentHashMap<String, WorkerWrapper>();
-  // all tasks that are assigned or need to be assigned
-  private final Map<String, TaskWrapper> tasks = new ConcurrentHashMap<String, TaskWrapper>();
+  private final Map<String, ZkWorker> zkWorkers = new ConcurrentHashMap<String, ZkWorker>();
+  // all tasks that have been assigned to a worker
+  private final TaskRunnerWorkQueue runningTasks = new TaskRunnerWorkQueue();
+  // tasks that have not yet run
+  private final TaskRunnerWorkQueue pendingTasks = new TaskRunnerWorkQueue();
+
+  private final ExecutorService runPendingTasksExec = Executors.newSingleThreadExecutor();
 
-  private final ConcurrentSkipListSet<String> currentlyProvisioning = new ConcurrentSkipListSet<String>();
-  private final ConcurrentSkipListSet<String> currentlyTerminating = new ConcurrentSkipListSet<String>();
   private final Object statusLock = new Object();
 
-  private volatile DateTime lastProvisionTime = new DateTime();
-  private volatile DateTime lastTerminateTime = new DateTime();
   private volatile boolean started = false;
 
   public RemoteTaskRunner(
@@ -112,7 +106,6 @@ public class RemoteTaskRunner implements TaskRunner
       PathChildrenCache workerPathCache,
       ScheduledExecutorService scheduledExec,
       RetryPolicyFactory retryPolicyFactory,
-      ScalingStrategy strategy,
       WorkerSetupManager workerSetupManager
   )
   {
@@ -122,7 +115,6 @@ public class RemoteTaskRunner implements TaskRunner
     this.workerPathCache = workerPathCache;
     this.scheduledExec = scheduledExec;
     this.retryPolicyFactory = retryPolicyFactory;
-    this.strategy = strategy;
     this.workerSetupManager = workerSetupManager;
   }
 
@@ -130,6 +122,11 @@ public class RemoteTaskRunner implements TaskRunner
   public void start()
   {
     try {
+      if (started) {
+        return;
+      }
+
+      // Add listener for creation/deletion of workers
       workerPathCache.getListenable().addListener(
           new PathChildrenCacheListener()
           {
@@ -156,77 +153,6 @@ public class RemoteTaskRunner implements TaskRunner
       );
       workerPathCache.start();
 
-      // Schedule termination of worker nodes periodically
-      Period period = new Period(config.getTerminateResourcesDuration());
-      PeriodGranularity granularity = new PeriodGranularity(period, config.getTerminateResourcesOriginDateTime(), null);
-      final long startTime = granularity.next(granularity.truncate(new DateTime().getMillis()));
-
-      ScheduledExecutors.scheduleAtFixedRate(
-          scheduledExec,
-          new Duration(
-              System.currentTimeMillis(),
-              startTime
-          ),
-          config.getTerminateResourcesDuration(),
-          new Runnable()
-          {
-            @Override
-            public void run()
-            {
-              if (currentlyTerminating.isEmpty()) {
-                if (zkWorkers.size() <= workerSetupManager.getWorkerSetupData().getMinNumWorkers()) {
-                  return;
-                }
-
-                int workerCount = 0;
-                List<WorkerWrapper> thoseLazyWorkers = Lists.newArrayList();
-                for (WorkerWrapper workerWrapper : zkWorkers.values()) {
-                  workerCount++;
-
-                  if (workerCount > workerSetupManager.getWorkerSetupData().getMinNumWorkers() &&
-                      workerWrapper.getRunningTasks().isEmpty() &&
-                      System.currentTimeMillis() - workerWrapper.getLastCompletedTaskTime().getMillis()
-                      > config.getMaxWorkerIdleTimeMillisBeforeDeletion()
-                      ) {
-                    thoseLazyWorkers.add(workerWrapper);
-                  }
-                }
-
-                AutoScalingData terminated = strategy.terminate(
-                    Lists.transform(
-                        thoseLazyWorkers,
-                        new Function<WorkerWrapper, String>()
-                        {
-                          @Override
-                          public String apply(WorkerWrapper input)
-                          {
-                            return input.getWorker().getIp();
-                          }
-                        }
-                    )
-                );
-
-                if (terminated != null) {
-                  currentlyTerminating.addAll(terminated.getNodeIds());
-                  lastTerminateTime = new DateTime();
-                }
-              } else {
-                Duration durSinceLastTerminate = new Duration(new DateTime(), lastTerminateTime);
-                if (durSinceLastTerminate.isLongerThan(config.getMaxScalingDuration())) {
-                  log.makeAlert("Worker node termination taking too long")
-                     .addData("millisSinceLastTerminate", durSinceLastTerminate.getMillis())
-                     .addData("terminatingCount", currentlyTerminating.size())
-                     .emit();
-                }
-
-                log.info(
-                    "%s still terminating. Wait for all nodes to terminate before trying again.",
-                    currentlyTerminating
-                );
-              }
-            }
-          }
-      );
       started = true;
     }
     catch (Exception e) {
@@ -238,8 +164,12 @@ public class RemoteTaskRunner implements TaskRunner
   public void stop()
   {
     try {
-      for (WorkerWrapper workerWrapper : zkWorkers.values()) {
-        workerWrapper.close();
+      if (!started) {
+        return;
+      }
+
+      for (ZkWorker zkWorker : zkWorkers.values()) {
+        zkWorker.close();
       }
     }
     catch (Exception e) {
@@ -250,119 +180,218 @@ public class RemoteTaskRunner implements TaskRunner
     }
   }
 
-  public boolean hasStarted()
+  @Override
+  public Collection<ZkWorker> getWorkers()
   {
-    return started;
-  }
-
-  public int getNumWorkers()
-  {
-    return zkWorkers.size();
+    return zkWorkers.values();
   }
 
   @Override
-  public void run(Task task, TaskContext context, TaskCallback callback)
+  public Collection<TaskRunnerWorkItem> getRunningTasks()
   {
-    if (tasks.containsKey(task.getId())) {
-      throw new ISE("Assigned a task[%s] that already exists, WTF is happening?!", task.getId());
-    }
-    TaskWrapper taskWrapper = new TaskWrapper(
-        task, context, callback, retryPolicyFactory.makeRetryPolicy()
-    );
-    tasks.put(taskWrapper.getTask().getId(), taskWrapper);
-    assignTask(taskWrapper);
+    return runningTasks.values();
   }
 
-  private void assignTask(TaskWrapper taskWrapper)
+  @Override
+  public Collection<TaskRunnerWorkItem> getPendingTasks()
   {
-    WorkerWrapper workerWrapper = findWorkerRunningTask(taskWrapper);
+    return pendingTasks.values();
+  }
 
-    // If the task already exists, we don't need to announce it
-    if (workerWrapper != null) {
-      final Worker worker = workerWrapper.getWorker();
-      try {
-        log.info("Worker[%s] is already running task[%s].", worker.getHost(), taskWrapper.getTask().getId());
+  public ZkWorker findWorkerRunningTask(String taskId)
+  {
+    for (ZkWorker zkWorker : zkWorkers.values()) {
+      if (zkWorker.getRunningTasks().contains(taskId)) {
+        return zkWorker;
+      }
+    }
+    return null;
+  }
 
-        TaskStatus taskStatus = jsonMapper.readValue(
-            workerWrapper.getStatusCache()
-                         .getCurrentData(
-                             JOINER.join(config.getStatusPath(), worker.getHost(), taskWrapper.getTask().getId())
-                         )
-                         .getData(),
-            TaskStatus.class
-        );
+  /**
+   * A task will be run only if there is no current knowledge in the RemoteTaskRunner of the task.
+   *
+   * @param task     task to run
+   * @param callback callback to be called exactly once
+   */
+  @Override
+  public void run(Task task, TaskCallback callback)
+  {
+    if (runningTasks.containsKey(task.getId()) || pendingTasks.containsKey(task.getId())) {
+      throw new ISE("Assigned a task[%s] that is already running or pending, WTF is happening?!", task.getId());
+    }
+    TaskRunnerWorkItem taskRunnerWorkItem = new TaskRunnerWorkItem(
+        task, callback, retryPolicyFactory.makeRetryPolicy(), new DateTime()
+    );
+    addPendingTask(taskRunnerWorkItem);
+  }
 
-        if (taskStatus.isComplete()) {
-          TaskCallback callback = taskWrapper.getCallback();
-          if (callback != null) {
-            callback.notify(taskStatus);
+  private void addPendingTask(final TaskRunnerWorkItem taskRunnerWorkItem)
+  {
+    log.info("Added pending task %s", taskRunnerWorkItem.getTask().getId());
+
+    pendingTasks.put(taskRunnerWorkItem.getTask().getId(), taskRunnerWorkItem);
+    runPendingTasks();
+  }
+
+  /**
+   * This method uses a single threaded executor to extract all pending tasks and attempt to run them. Any tasks that
+   * are successfully assigned to a worker will be moved from pendingTasks to runningTasks. This method is thread-safe.
+   * This method should be run each time there is new worker capacity or if new tasks are assigned.
+   */
+  private void runPendingTasks()
+  {
+    Future future = runPendingTasksExec.submit(
+        new Callable<Void>()
+        {
+          @Override
+          public Void call() throws Exception
+          {
+            // make a copy of the pending tasks because assignTask may delete tasks from pending and move them
+            // into running status
+            List<TaskRunnerWorkItem> copy = Lists.newArrayList(pendingTasks.values());
+            for (TaskRunnerWorkItem taskWrapper : copy) {
+              assignTask(taskWrapper);
+            }
+
+            return null;
           }
-          new CleanupPaths(worker.getHost(), taskWrapper.getTask().getId()).run();
         }
-      }
-      catch (Exception e) {
-        log.error(e, "Task exists, but hit exception!");
-        retryTask(new CleanupPaths(worker.getHost(), taskWrapper.getTask().getId()), taskWrapper);
-      }
-    } else {
-      // Announce the task or retry if there is not enough capacity
-      workerWrapper = findWorkerForTask();
-      if (workerWrapper != null) {
-        announceTask(workerWrapper.getWorker(), taskWrapper);
-      } else {
-        retryTask(null, taskWrapper);
-      }
+    );
+
+    try {
+      future.get();
+    }
+    catch (InterruptedException e) {
+      log.error(e, "InterruptedException in runPendingTasks()");
+      throw Throwables.propagate(e);
+    }
+    catch (ExecutionException e) {
+      log.error(e, "ExecutionException in runPendingTasks()");
+      throw Throwables.propagate(e.getCause());
     }
   }
 
   /**
-   * Retries a task that has failed.
+   * Retries a task by inserting it back into the pending queue after a given delay.
+   * This method will also clean up any status paths that were associated with the task.
    *
-   * @param pre         - A runnable that is executed before the retry occurs
-   * @param taskWrapper - a container for task properties
+   * @param taskRunnerWorkItem - the task to retry
+   * @param workerId           - the worker that was previously running this task
    */
-  private void retryTask(
-      final Runnable pre,
-      final TaskWrapper taskWrapper
-  )
+  private void retryTask(final TaskRunnerWorkItem taskRunnerWorkItem, final String workerId)
   {
-    final Task task = taskWrapper.getTask();
-    final RetryPolicy retryPolicy = taskWrapper.getRetryPolicy();
-
-    log.info("Registering retry for failed task[%s]", task.getId());
-
-    if (retryPolicy.hasExceededRetryThreshold()) {
-      log.makeAlert("Task exceeded maximum retry count")
-         .addData("task", task.getId())
-         .addData("retryCount", retryPolicy.getNumRetries())
-         .emit();
-      return;
-    }
-
+    final String taskId = taskRunnerWorkItem.getTask().getId();
+    log.info("Retry scheduled in %s for %s", taskRunnerWorkItem.getRetryPolicy().getRetryDelay(), taskId);
     scheduledExec.schedule(
         new Runnable()
         {
           @Override
           public void run()
           {
-            if (pre != null) {
-              pre.run();
-            }
-
-            if (tasks.containsKey(task.getId())) {
-              log.info("Retry[%d] for task[%s]", retryPolicy.getNumRetries(), task.getId());
-              assignTask(taskWrapper);
-            }
+            cleanup(workerId, taskId);
+            addPendingTask(taskRunnerWorkItem);
           }
         },
-        retryPolicy.getAndIncrementRetryDelay().getMillis(),
+        taskRunnerWorkItem.getRetryPolicy().getAndIncrementRetryDelay().getMillis(),
         TimeUnit.MILLISECONDS
     );
   }
 
   /**
-   * When a new worker appears, listeners are registered for status changes.
-   * Status changes indicate the creation or completion of task.
+   * Removes a task from the running queue and clears out the ZK status path of the task.
+   *
+   * @param workerId - the worker that was previously running the task
+   * @param taskId   - the task to cleanup
+   */
+  private void cleanup(final String workerId, final String taskId)
+  {
+    runningTasks.remove(taskId);
+    final String statusPath = JOINER.join(config.getStatusPath(), workerId, taskId);
+    try {
+      cf.delete().guaranteed().forPath(statusPath);
+    }
+    catch (Exception e) {
+      log.info("Tried to delete status path[%s] that didn't exist! Must've gone away already?", statusPath);
+    }
+  }
+
+  /**
+   * Ensures no workers are already running a task before assigning the task to a worker.
+   * It is possible that a worker is running a task that the RTR has no knowledge of. This occurs when the RTR
+   * needs to bootstrap after a restart.
+   *
+   * @param taskRunnerWorkItem - the task to assign
+   */
+  private void assignTask(TaskRunnerWorkItem taskRunnerWorkItem)
+  {
+    try {
+      final String taskId = taskRunnerWorkItem.getTask().getId();
+      ZkWorker zkWorker = findWorkerRunningTask(taskId);
+
+      // If a worker is already running this task, we don't need to announce it
+      if (zkWorker != null) {
+        final Worker worker = zkWorker.getWorker();
+        log.info("Worker[%s] is already running task[%s].", worker.getHost(), taskId);
+        runningTasks.put(taskId, pendingTasks.remove(taskId));
+        log.info("Task %s switched from pending to running", taskId);
+      } else {
+        // Nothing running this task, announce it in ZK for a worker to run it
+        zkWorker = findWorkerForTask();
+        if (zkWorker != null) {
+          announceTask(zkWorker.getWorker(), taskRunnerWorkItem);
+        }
+      }
+    }
+    catch (Exception e) {
+      throw Throwables.propagate(e);
+    }
+  }
+
+  /**
+   * Creates a ZK entry under a specific path associated with a worker. The worker is responsible for
+   * removing the task ZK entry and creating a task status ZK entry.
+   *
+   * @param theWorker          The worker the task is assigned to
+   * @param taskRunnerWorkItem The task to be assigned
+   */
+  private void announceTask(Worker theWorker, TaskRunnerWorkItem taskRunnerWorkItem) throws Exception
+  {
+    final Task task = taskRunnerWorkItem.getTask();
+
+    log.info("Coordinator asking Worker[%s] to add task[%s]", theWorker.getHost(), task.getId());
+
+    byte[] rawBytes = jsonMapper.writeValueAsBytes(task);
+    if (rawBytes.length > config.getMaxNumBytes()) {
+      throw new ISE("Length of raw bytes for task too large[%,d > %,d]", rawBytes.length, config.getMaxNumBytes());
+    }
+
+    cf.create()
+      .withMode(CreateMode.EPHEMERAL)
+      .forPath(
+          JOINER.join(
+              config.getTaskPath(),
+              theWorker.getHost(),
+              task.getId()
+          ),
+          rawBytes
+      );
+
+    runningTasks.put(task.getId(), pendingTasks.remove(task.getId()));
+    log.info("Task %s switched from pending to running", task.getId());
+
+    // Syncing state with Zookeeper - don't assign new tasks until the task we just assigned is actually running
+    // on a worker - this avoids overflowing a worker with tasks
+    synchronized (statusLock) {
+      while (findWorkerRunningTask(task.getId()) == null) {
+        statusLock.wait(config.getTaskAssignmentTimeoutDuration().getMillis());
+      }
+    }
+  }
+
+  /**
+   * When a new worker appears, listeners are registered for status changes associated with tasks assigned to
+   * the worker. Status changes indicate the creation or completion of a task.
    * The RemoteTaskRunner updates state according to these changes.
    *
    * @param worker - contains metadata for a worker that has appeared in ZK
@@ -370,11 +399,9 @@ public class RemoteTaskRunner implements TaskRunner
   private void addWorker(final Worker worker)
   {
     try {
-      currentlyProvisioning.removeAll(strategy.ipLookup(Arrays.<String>asList(worker.getIp())));
-
       final String workerStatusPath = JOINER.join(config.getStatusPath(), worker.getHost());
       final PathChildrenCache statusCache = new PathChildrenCache(cf, workerStatusPath, true);
-      final WorkerWrapper workerWrapper = new WorkerWrapper(
+      final ZkWorker zkWorker = new ZkWorker(
           worker,
           statusCache,
           jsonMapper
@@ -387,146 +414,153 @@ public class RemoteTaskRunner implements TaskRunner
             @Override
             public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception
             {
-              synchronized (statusLock) {
-                try {
-                  if (event.getType().equals(PathChildrenCacheEvent.Type.CHILD_ADDED) ||
-                      event.getType().equals(PathChildrenCacheEvent.Type.CHILD_UPDATED)) {
-                    final String taskId = ZKPaths.getNodeFromPath(event.getData().getPath());
-                    final TaskStatus taskStatus;
 
-                    // This can fail if a worker writes a bogus status. Retry if so.
-                    try {
-                      taskStatus = jsonMapper.readValue(
-                          event.getData().getData(), TaskStatus.class
-                      );
+              try {
+                if (event.getType().equals(PathChildrenCacheEvent.Type.CHILD_ADDED) ||
+                    event.getType().equals(PathChildrenCacheEvent.Type.CHILD_UPDATED)) {
+                  final String taskId = ZKPaths.getNodeFromPath(event.getData().getPath());
+                  final TaskStatus taskStatus;
 
-                      if (!taskStatus.getId().equals(taskId)) {
-                        // Sanity check
-                        throw new ISE(
-                            "Worker[%s] status id does not match payload id: %s != %s",
-                            worker.getHost(),
-                            taskId,
-                            taskStatus.getId()
-                        );
-                      }
-                    }
-                    catch (Exception e) {
-                      log.warn(e, "Worker[%s] wrote bogus status for task: %s", worker.getHost(), taskId);
-                      retryTask(new CleanupPaths(worker.getHost(), taskId), tasks.get(taskId));
-                      throw Throwables.propagate(e);
-                    }
-
-                    log.info(
-                        "Worker[%s] wrote %s status for task: %s",
-                        worker.getHost(),
-                        taskStatus.getStatusCode(),
-                        taskId
+                  // This can fail if a worker writes a bogus status. Retry if so.
+                  try {
+                    taskStatus = jsonMapper.readValue(
+                        event.getData().getData(), TaskStatus.class
                     );
 
-                    statusLock.notify();
-
-                    if (taskStatus.isComplete()) {
-                      // Worker is done with this task
-                      workerWrapper.setLastCompletedTaskTime(new DateTime());
-                      final TaskWrapper taskWrapper = tasks.get(taskId);
-
-                      if (taskWrapper == null) {
-                        log.warn(
-                            "WTF?! Worker[%s] completed a task I didn't know about: %s",
-                            worker.getHost(),
-                            taskId
-                        );
-                      } else {
-                        final TaskCallback callback = taskWrapper.getCallback();
-
-                        // Cleanup
-                        if (callback != null) {
-                          callback.notify(taskStatus);
-                        }
-                        tasks.remove(taskId);
-                        cf.delete().guaranteed().inBackground().forPath(event.getData().getPath());
-                      }
+                    if (!taskStatus.getId().equals(taskId)) {
+                      // Sanity check
+                      throw new ISE(
+                          "Worker[%s] status id does not match payload id: %s != %s",
+                          worker.getHost(),
+                          taskId,
+                          taskStatus.getId()
+                      );
                     }
                   }
+                  catch (Exception e) {
+                    log.warn(e, "Worker[%s] wrote bogus status for task: %s", worker.getHost(), taskId);
+                    retryTask(runningTasks.get(taskId), worker.getHost());
+                    throw Throwables.propagate(e);
+                  }
+
+                  log.info(
+                      "Worker[%s] wrote %s status for task: %s",
+                      worker.getHost(),
+                      taskStatus.getStatusCode(),
+                      taskId
+                  );
+
+                  // Synchronizing state with ZK
+                  synchronized (statusLock) {
+                    statusLock.notify();
+                  }
+
+                  final TaskRunnerWorkItem taskRunnerWorkItem = runningTasks.get(taskId);
+                  if (taskRunnerWorkItem == null) {
+                    log.warn(
+                        "WTF?! Worker[%s] announcing a status for a task I didn't know about: %s",
+                        worker.getHost(),
+                        taskId
+                    );
+                  }
+
+                  if (taskStatus.isComplete()) {
+                    if (taskRunnerWorkItem != null) {
+                      final TaskCallback callback = taskRunnerWorkItem.getCallback();
+                      if (callback != null) {
+                        callback.notify(taskStatus);
+                      }
+                    }
+
+                    // Worker is done with this task
+                    zkWorker.setLastCompletedTaskTime(new DateTime());
+                    cleanup(worker.getHost(), taskId);
+                    runPendingTasks();
+                  }
+                } else if (event.getType().equals(PathChildrenCacheEvent.Type.CHILD_REMOVED)) {
+                  final String taskId = ZKPaths.getNodeFromPath(event.getData().getPath());
+                  if (runningTasks.containsKey(taskId)) {
+                    log.info("Task %s just disappeared!", taskId);
+                    retryTask(runningTasks.get(taskId), worker.getHost());
+                  }
                 }
-                catch (Exception e) {
-                  log.makeAlert(e, "Failed to handle new worker status")
-                     .addData("worker", worker.getHost())
-                     .addData("znode", event.getData().getPath())
-                     .emit();
-                }
+              }
+              catch (Exception e) {
+                log.makeAlert(e, "Failed to handle new worker status")
+                   .addData("worker", worker.getHost())
+                   .addData("znode", event.getData().getPath())
+                   .emit();
               }
             }
           }
       );
-      zkWorkers.put(worker.getHost(), workerWrapper);
+      zkWorkers.put(worker.getHost(), zkWorker);
       statusCache.start();
+
+      runPendingTasks();
     }
     catch (Exception e) {
       throw Throwables.propagate(e);
     }
   }
 
-  private WorkerWrapper findWorkerRunningTask(TaskWrapper taskWrapper)
-  {
-    for (WorkerWrapper workerWrapper : zkWorkers.values()) {
-      if (workerWrapper.getRunningTasks().contains(taskWrapper.getTask().getId())) {
-        return workerWrapper;
-      }
-    }
-    return null;
-  }
-
   /**
-   * When a ephemeral worker node disappears from ZK, we have to make sure there are no tasks still assigned
-   * to the worker. If tasks remain, they are retried.
+   * When a ephemeral worker node disappears from ZK, incomplete running tasks will be retried by
+   * the logic in the status listener. We still have to make sure there are no tasks assigned
+   * to the worker but not yet running.
    *
    * @param worker - the removed worker
    */
   private void removeWorker(final Worker worker)
   {
-    currentlyTerminating.remove(worker.getHost());
-
-    WorkerWrapper workerWrapper = zkWorkers.get(worker.getHost());
-    if (workerWrapper != null) {
+    ZkWorker zkWorker = zkWorkers.get(worker.getHost());
+    if (zkWorker != null) {
       try {
-        Set<String> tasksToRetry = Sets.newHashSet(workerWrapper.getRunningTasks());
-        tasksToRetry.addAll(cf.getChildren().forPath(JOINER.join(config.getTaskPath(), worker.getHost())));
+        Set<String> tasksPending = Sets.newHashSet(
+            cf.getChildren()
+              .forPath(JOINER.join(config.getTaskPath(), worker.getHost()))
+        );
+        log.info("%s had %d tasks pending", worker.getHost(), tasksPending.size());
 
-        for (String taskId : tasksToRetry) {
-          TaskWrapper taskWrapper = tasks.get(taskId);
-          if (taskWrapper != null) {
-            retryTask(new CleanupPaths(worker.getHost(), taskId), tasks.get(taskId));
+        for (String taskId : tasksPending) {
+          TaskRunnerWorkItem taskRunnerWorkItem = pendingTasks.get(taskId);
+          if (taskRunnerWorkItem != null) {
+            cf.delete().guaranteed().forPath(JOINER.join(config.getTaskPath(), worker.getHost(), taskId));
+            retryTask(taskRunnerWorkItem, worker.getHost());
+          } else {
+            log.warn("RemoteTaskRunner has no knowledge of pending task %s", taskId);
           }
         }
 
-        workerWrapper.getStatusCache().close();
+        zkWorker.getStatusCache().close();
       }
       catch (Exception e) {
-        log.error(e, "Failed to cleanly remove worker[%s]");
+        throw Throwables.propagate(e);
+      }
+      finally {
+        zkWorkers.remove(worker.getHost());
       }
     }
-    zkWorkers.remove(worker.getHost());
   }
 
-  private WorkerWrapper findWorkerForTask()
+  private ZkWorker findWorkerForTask()
   {
     try {
-      final MinMaxPriorityQueue<WorkerWrapper> workerQueue = MinMaxPriorityQueue.<WorkerWrapper>orderedBy(
-          new Comparator<WorkerWrapper>()
+      final MinMaxPriorityQueue<ZkWorker> workerQueue = MinMaxPriorityQueue.<ZkWorker>orderedBy(
+          new Comparator<ZkWorker>()
           {
             @Override
-            public int compare(WorkerWrapper w1, WorkerWrapper w2)
+            public int compare(ZkWorker w1, ZkWorker w2)
             {
               return -Ints.compare(w1.getRunningTasks().size(), w2.getRunningTasks().size());
             }
           }
       ).create(
           FunctionalIterable.create(zkWorkers.values()).filter(
-              new Predicate<WorkerWrapper>()
+              new Predicate<ZkWorker>()
               {
                 @Override
-                public boolean apply(WorkerWrapper input)
+                public boolean apply(ZkWorker input)
                 {
                   return (!input.isAtCapacity() &&
                           input.getWorker()
@@ -538,28 +572,7 @@ public class RemoteTaskRunner implements TaskRunner
       );
 
       if (workerQueue.isEmpty()) {
-        log.info("Worker nodes do not have capacity to run any more tasks!");
-
-        if (currentlyProvisioning.isEmpty()) {
-          AutoScalingData provisioned = strategy.provision();
-          if (provisioned != null) {
-            currentlyProvisioning.addAll(provisioned.getNodeIds());
-            lastProvisionTime = new DateTime();
-          }
-        } else {
-          Duration durSinceLastProvision = new Duration(new DateTime(), lastProvisionTime);
-          if (durSinceLastProvision.isLongerThan(config.getMaxScalingDuration())) {
-            log.makeAlert("Worker node provisioning taking too long")
-               .addData("millisSinceLastProvision", durSinceLastProvision.getMillis())
-               .addData("provisioningCount", currentlyProvisioning.size())
-               .emit();
-          }
-
-          log.info(
-              "%s still provisioning. Wait for all provisioned nodes to complete before requesting new worker.",
-              currentlyProvisioning
-          );
-        }
+        log.info("Worker nodes %s do not have capacity to run any more tasks!", zkWorkers.values());
         return null;
       }
 
@@ -569,82 +582,4 @@ public class RemoteTaskRunner implements TaskRunner
       throw Throwables.propagate(e);
     }
   }
-
-  /**
-   * Creates a ZK entry under a specific path associated with a worker. The worker is responsible for
-   * removing the task ZK entry and creating a task status ZK entry.
-   *
-   * @param theWorker   The worker the task is assigned to
-   * @param taskWrapper The task to be assigned
-   */
-  private void announceTask(Worker theWorker, TaskWrapper taskWrapper)
-  {
-    synchronized (statusLock) {
-      final Task task = taskWrapper.getTask();
-      final TaskContext taskContext = taskWrapper.getTaskContext();
-      try {
-        log.info("Coordinator asking Worker[%s] to add task[%s]", theWorker.getHost(), task.getId());
-
-        tasks.put(task.getId(), taskWrapper);
-
-        byte[] rawBytes = jsonMapper.writeValueAsBytes(new TaskHolder(task, taskContext));
-
-        if (rawBytes.length > config.getMaxNumBytes()) {
-          throw new ISE("Length of raw bytes for task too large[%,d > %,d]", rawBytes.length, config.getMaxNumBytes());
-        }
-
-        cf.create()
-          .withMode(CreateMode.EPHEMERAL)
-          .forPath(
-              JOINER.join(
-                  config.getTaskPath(),
-                  theWorker.getHost(),
-                  task.getId()
-              ),
-              jsonMapper.writeValueAsBytes(new TaskHolder(task, taskContext))
-          );
-
-        // Syncing state with Zookeeper
-        while (findWorkerRunningTask(taskWrapper) == null) {
-          statusLock.wait(config.getTaskAssignmentTimeoutDuration().getMillis());
-        }
-      }
-      catch (Exception e) {
-        log.error(e, "Exception creating task[%s] for worker node[%s]", task.getId(), theWorker.getHost());
-        throw Throwables.propagate(e);
-      }
-    }
-  }
-
-  private class CleanupPaths implements Runnable
-  {
-    private final String workerId;
-    private final String taskId;
-
-    private CleanupPaths(String workerId, String taskId)
-    {
-      this.workerId = workerId;
-      this.taskId = taskId;
-    }
-
-    @Override
-    public void run()
-    {
-      try {
-        final String statusPath = JOINER.join(config.getStatusPath(), workerId, taskId);
-        cf.delete().guaranteed().forPath(statusPath);
-      }
-      catch (Exception e) {
-        log.warn("Tried to delete a status path that didn't exist! Must've gone away already?");
-      }
-
-      try {
-        final String taskPath = JOINER.join(config.getTaskPath(), workerId, taskId);
-        cf.delete().guaranteed().forPath(taskPath);
-      }
-      catch (Exception e) {
-        log.warn("Tried to delete a task path that didn't exist! Must've gone away already?");
-      }
-    }
-  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/RetryPolicy.java

@@ -44,6 +44,11 @@ public class RetryPolicy
     this.retryCount = 0;
   }
 
+  public Duration getRetryDelay()
+  {
+    return currRetryDelay;
+  }
+
   public Duration getAndIncrementRetryDelay()
   {
     Duration retVal = new Duration(currRetryDelay);

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskExistsException.java

@@ -0,0 +1,22 @@
+package com.metamx.druid.merger.coordinator;
+
+public class TaskExistsException extends RuntimeException
+{
+  private final String taskId;
+
+  public TaskExistsException(String taskId, Throwable t)
+  {
+    super(String.format("Task exists: %s", taskId), t);
+    this.taskId = taskId;
+  }
+
+  public TaskExistsException(String taskId)
+  {
+    this(taskId, null);
+  }
+
+  public String getTaskId()
+  {
+    return taskId;
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskLockbox.java

@@ -0,0 +1,405 @@
+package com.metamx.druid.merger.coordinator;
+
+import com.google.common.base.Function;
+import com.google.common.base.Optional;
+import com.google.common.base.Predicate;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import com.google.common.collect.Sets;
+import com.metamx.common.IAE;
+import com.metamx.common.guava.Comparators;
+import com.metamx.common.guava.FunctionalIterable;
+import com.metamx.druid.merger.common.TaskLock;
+import com.metamx.druid.merger.common.task.Task;
+import com.metamx.emitter.EmittingLogger;
+import org.joda.time.DateTime;
+import org.joda.time.Interval;
+
+import javax.annotation.Nullable;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.NavigableMap;
+import java.util.NavigableSet;
+import java.util.Set;
+import java.util.TreeMap;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * Remembers which tasks have locked which intervals. Tasks are permitted to lock an interval if no other task
+ * outside their group has locked an overlapping interval for the same datasource. When a task locks an interval,
+ * it is assigned a version string that it can use to publish segments.
+ */
+public class TaskLockbox
+{
+  // Datasource -> Interval -> Tasks + TaskLock
+  private final Map<String, NavigableMap<Interval, TaskLockPosse>> running = Maps.newHashMap();
+  private final TaskStorage taskStorage;
+  private final ReentrantLock giant = new ReentrantLock();
+
+  private static final EmittingLogger log = new EmittingLogger(TaskLockbox.class);
+
+  public TaskLockbox(TaskStorage taskStorage)
+  {
+    this.taskStorage = taskStorage;
+  }
+
+  /**
+   * Attempt to lock a task, without removing it from the queue. Equivalent to the long form of {@code tryLock}
+   * with no preferred version.
+   *
+   * @param task task to attempt to lock
+   *
+   * @return lock version if lock was acquired, absent otherwise
+   */
+  public Optional<TaskLock> tryLock(final Task task, final Interval interval)
+  {
+    return tryLock(task, interval, Optional.<String>absent());
+  }
+
+  /**
+   * Attempt to lock a task, without removing it from the queue. Can safely be called multiple times on the same task.
+   * This method will attempt to assign version strings that obey the invariant that every version string is
+   * lexicographically greater than any other version string previously assigned to the same interval. This invariant
+   * is only mostly guaranteed, however; we assume clock monotonicity and we assume that callers specifying
+   * {@code preferredVersion} are doing the right thing.
+   *
+   * @param task             task to attempt to lock
+   * @param preferredVersion use this version string if one has not yet been assigned
+   *
+   * @return lock version if lock was acquired, absent otherwise
+   */
+  public Optional<TaskLock> tryLock(final Task task, final Interval interval, final Optional<String> preferredVersion)
+  {
+    giant.lock();
+
+    try {
+
+      if(task.getFixedInterval().isPresent() && !task.getFixedInterval().get().equals(interval)) {
+        // Task may only lock its fixed interval, if present
+        throw new IAE("Task must lock its fixed interval: %s", task.getId());
+      }
+
+      final String dataSource = task.getDataSource();
+      final List<TaskLockPosse> foundPosses = findLockPossesForInterval(dataSource, interval);
+      final TaskLockPosse posseToUse;
+
+      if (foundPosses.size() > 1) {
+
+        // Too many existing locks.
+        return Optional.absent();
+
+      } else if (foundPosses.size() == 1) {
+
+        // One existing lock -- check if we can add to it.
+
+        final TaskLockPosse foundPosse = Iterables.getOnlyElement(foundPosses);
+        if (foundPosse.getTaskLock().getInterval().contains(interval) && foundPosse.getTaskLock().getGroupId().equals(task.getGroupId())) {
+          posseToUse = foundPosse;
+        } else {
+          return Optional.absent();
+        }
+
+      } else {
+
+        // No existing locks. We can make a new one.
+        if (!running.containsKey(dataSource)) {
+          running.put(dataSource, new TreeMap<Interval, TaskLockPosse>(Comparators.intervalsByStartThenEnd()));
+        }
+
+        // Create new TaskLock and assign it a version.
+        // Assumption: We'll choose a version that is greater than any previously-chosen version for our interval. (This
+        // may not always be true, unfortunately. See below.)
+
+        final String version;
+
+        if (preferredVersion.isPresent()) {
+          // We have a preferred version. We'll trust our caller to not break our ordering assumptions and just use it.
+          version = preferredVersion.get();
+        } else {
+          // We are running under an interval lock right now, so just using the current time works as long as we can trust
+          // our clock to be monotonic and have enough resolution since the last time we created a TaskLock for the same
+          // interval. This may not always be true; to assure it we would need to use some method of timekeeping other
+          // than the wall clock.
+          version = new DateTime().toString();
+        }
+
+        posseToUse = new TaskLockPosse(new TaskLock(task.getGroupId(), dataSource, interval, version));
+        running.get(dataSource)
+               .put(interval, posseToUse);
+
+        log.info("Created new TaskLockPosse: %s", posseToUse);
+      }
+
+      // Add to existing TaskLockPosse, if necessary
+      if (posseToUse.getTaskIds().add(task.getId())) {
+        log.info("Added task[%s] to TaskLock[%s]", task.getId(), posseToUse.getTaskLock().getGroupId());
+
+        // Best effort to update task storage facility
+        try {
+          taskStorage.addLock(task.getId(), posseToUse.getTaskLock());
+        } catch(Exception e) {
+          log.makeAlert("Failed to persist lock in storage")
+             .addData("task", task.getId())
+             .addData("dataSource", posseToUse.getTaskLock().getDataSource())
+             .addData("interval", posseToUse.getTaskLock().getInterval())
+             .addData("version", posseToUse.getTaskLock().getVersion())
+             .emit();
+        }
+      } else {
+        log.info("Task[%s] already present in TaskLock[%s]", task.getId(), posseToUse.getTaskLock().getGroupId());
+      }
+
+      return Optional.of(posseToUse.getTaskLock());
+    }
+    finally {
+      giant.unlock();
+    }
+
+  }
+
+  /**
+   * Return the currently-active locks for some task.
+   *
+   * @param task task for which to locate locks
+   */
+  public List<TaskLock> findLocksForTask(final Task task)
+  {
+    giant.lock();
+
+    try {
+      return Lists.transform(
+          findLockPossesForTask(task), new Function<TaskLockPosse, TaskLock>()
+      {
+        @Override
+        public TaskLock apply(TaskLockPosse taskLockPosse)
+        {
+          return taskLockPosse.getTaskLock();
+        }
+      }
+      );
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  /**
+   * Release lock held for a task on a particular interval. Does nothing if the task does not currently
+   * hold the mentioned lock.
+   *
+   * @param task task to unlock
+   * @param interval interval to unlock
+   */
+  public void unlock(final Task task, final Interval interval)
+  {
+    giant.lock();
+
+    try {
+      final String dataSource = task.getDataSource();
+      final NavigableMap<Interval, TaskLockPosse> dsRunning = running.get(dataSource);
+
+      // So we can alert if tasks try to release stuff they don't have
+      boolean removed = false;
+
+      if(dsRunning != null) {
+        final TaskLockPosse taskLockPosse = dsRunning.get(interval);
+        if(taskLockPosse != null) {
+          final TaskLock taskLock = taskLockPosse.getTaskLock();
+
+          // Remove task from live list
+          log.info("Removing task[%s] from TaskLock[%s]", task.getId(), taskLock.getGroupId());
+          removed = taskLockPosse.getTaskIds().remove(task.getId());
+
+          if (taskLockPosse.getTaskIds().isEmpty()) {
+            log.info("TaskLock is now empty: %s", taskLock);
+            running.get(dataSource).remove(taskLock.getInterval());
+          }
+
+          if (running.get(dataSource).size() == 0) {
+            running.remove(dataSource);
+          }
+
+          // Best effort to remove lock from storage
+          try {
+            taskStorage.removeLock(task.getId(), taskLock);
+          } catch(Exception e) {
+            log.makeAlert(e, "Failed to clean up lock from storage")
+               .addData("task", task.getId())
+               .addData("dataSource", taskLock.getDataSource())
+               .addData("interval", taskLock.getInterval())
+               .addData("version", taskLock.getVersion())
+               .emit();
+          }
+        }
+      }
+
+      if(!removed) {
+        log.makeAlert("Lock release without acquire")
+           .addData("task", task.getId())
+           .addData("interval", interval)
+           .emit();
+      }
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  /**
+   * Release all locks for a task. Does nothing if the task is not currently locked.
+   *
+   * @param task task to unlock
+   */
+  public void unlock(final Task task)
+  {
+    giant.lock();
+
+    try {
+      for(final TaskLockPosse taskLockPosse : findLockPossesForTask(task)) {
+        unlock(task, taskLockPosse.getTaskLock().getInterval());
+      }
+    }
+    finally {
+      giant.unlock();
+    }
+  }
+
+  /**
+   * Removes all locks from this lockbox.
+   */
+  public void clear()
+  {
+    giant.lock();
+
+    try {
+      running.clear();
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  /**
+   * Return the currently-active lock posses for some task.
+   *
+   * @param task task for which to locate locks
+   */
+  private List<TaskLockPosse> findLockPossesForTask(final Task task)
+  {
+    giant.lock();
+
+    try {
+      final Iterable<TaskLockPosse> searchSpace;
+
+      if (task.getFixedInterval().isPresent()) {
+        // Narrow down search using findLockPossesForInterval
+        searchSpace = findLockPossesForInterval(task.getDataSource(), task.getFixedInterval().get());
+      } else {
+        // Scan through all locks for this datasource
+        final NavigableMap<Interval, TaskLockPosse> dsRunning = running.get(task.getDataSource());
+        if(dsRunning == null) {
+          searchSpace = ImmutableList.of();
+        } else {
+          searchSpace = dsRunning.values();
+        }
+      }
+
+      return ImmutableList.copyOf(
+          Iterables.filter(
+              searchSpace, new Predicate<TaskLockPosse>()
+          {
+            @Override
+            public boolean apply(TaskLockPosse taskLock)
+            {
+              return taskLock.getTaskIds().contains(task.getId());
+            }
+          }
+          )
+      );
+    }
+    finally {
+      giant.unlock();
+    }
+  }
+
+  /**
+   * Return all locks that overlap some search interval.
+   */
+  private List<TaskLockPosse> findLockPossesForInterval(final String dataSource, final Interval interval)
+  {
+    giant.lock();
+
+    try {
+      final NavigableMap<Interval, TaskLockPosse> dsRunning = running.get(dataSource);
+      if (dsRunning == null) {
+        // No locks at all
+        return Collections.emptyList();
+      } else {
+        // Tasks are indexed by locked interval, which are sorted by interval start. Intervals are non-overlapping, so:
+        final NavigableSet<Interval> dsLockbox = dsRunning.navigableKeySet();
+        final Iterable<Interval> searchIntervals = Iterables.concat(
+            // Single interval that starts at or before ours
+            Collections.singletonList(dsLockbox.floor(new Interval(interval.getStart(), new DateTime(Long.MAX_VALUE)))),
+
+            // All intervals that start somewhere between our start instant (exclusive) and end instant (exclusive)
+            dsLockbox.subSet(
+                new Interval(interval.getStart(), new DateTime(Long.MAX_VALUE)),
+                false,
+                new Interval(interval.getEnd(), interval.getEnd()),
+                false
+            )
+        );
+
+        return Lists.newArrayList(
+            FunctionalIterable
+                .create(searchIntervals)
+                .filter(
+                    new Predicate<Interval>()
+                    {
+                      @Override
+                      public boolean apply(@Nullable Interval searchInterval)
+                      {
+                        return searchInterval != null && searchInterval.overlaps(interval);
+                      }
+                    }
+                )
+                .transform(
+                    new Function<Interval, TaskLockPosse>()
+                    {
+                      @Override
+                      public TaskLockPosse apply(Interval interval)
+                      {
+                        return dsRunning.get(interval);
+                      }
+                    }
+                )
+        );
+      }
+    }
+    finally {
+      giant.unlock();
+    }
+  }
+
+  private static class TaskLockPosse
+  {
+    final private TaskLock taskLock;
+    final private Set<String> taskIds;
+
+    public TaskLockPosse(TaskLock taskLock)
+    {
+      this.taskLock = taskLock;
+      taskIds = Sets.newHashSet();
+    }
+
+    public TaskLock getTaskLock()
+    {
+      return taskLock;
+    }
+
+    public Set<String> getTaskIds()
+    {
+      return taskIds;
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskMasterLifecycle.java

@@ -25,8 +25,11 @@ import com.metamx.common.lifecycle.LifecycleStart;
 import com.metamx.common.lifecycle.LifecycleStop;
 import com.metamx.druid.initialization.Initialization;
 import com.metamx.druid.initialization.ServiceDiscoveryConfig;
+import com.metamx.druid.merger.common.TaskToolbox;
 import com.metamx.druid.merger.coordinator.config.IndexerCoordinatorConfig;
 import com.metamx.druid.merger.coordinator.exec.TaskConsumer;
+import com.metamx.druid.merger.coordinator.scaling.ResourceManagementScheduler;
+import com.metamx.druid.merger.coordinator.scaling.ResourceManagementSchedulerFactory;
 import com.metamx.emitter.EmittingLogger;
 import com.metamx.emitter.service.ServiceEmitter;
 import com.netflix.curator.framework.CuratorFramework;
@@ -40,26 +43,33 @@ import java.util.concurrent.locks.ReentrantLock;
 /**
  * Encapsulates the indexer leadership lifecycle.
  */
-public class TaskMaster
+public class TaskMasterLifecycle
 {
   private final LeaderSelector leaderSelector;
   private final ReentrantLock giant = new ReentrantLock();
   private final Condition mayBeStopped = giant.newCondition();
+  private final TaskQueue taskQueue;
+  private final TaskToolbox taskToolbox;
 
   private volatile boolean leading = false;
+  private volatile TaskRunner theRunner;
 
-  private static final EmittingLogger log = new EmittingLogger(TaskMaster.class);
+  private static final EmittingLogger log = new EmittingLogger(TaskMasterLifecycle.class);
 
-  public TaskMaster(
-      final TaskQueue queue,
+  public TaskMasterLifecycle(
+      final TaskQueue taskQueue,
+      final TaskToolbox taskToolbox,
       final IndexerCoordinatorConfig indexerCoordinatorConfig,
       final ServiceDiscoveryConfig serviceDiscoveryConfig,
-      final MergerDBCoordinator mergerDBCoordinator,
       final TaskRunnerFactory runnerFactory,
+      final ResourceManagementSchedulerFactory managementSchedulerFactory,
       final CuratorFramework curator,
       final ServiceEmitter emitter
-      )
+  )
   {
+    this.taskQueue = taskQueue;
+    this.taskToolbox = taskToolbox;
+
     this.leaderSelector = new LeaderSelector(
         curator, indexerCoordinatorConfig.getLeaderLatchPath(), new LeaderSelectorListener()
     {
@@ -71,31 +81,45 @@ public class TaskMaster
         try {
           log.info("By the power of Grayskull, I have the power!");
 
-          final TaskRunner runner = runnerFactory.build();
-          final TaskConsumer consumer = new TaskConsumer(queue, runner, mergerDBCoordinator, emitter);
+          final TaskRunner taskRunner = runnerFactory.build();
+          theRunner = taskRunner;
+          final ResourceManagementScheduler scheduler = managementSchedulerFactory.build(theRunner);
+          final TaskConsumer taskConsumer = new TaskConsumer(
+              taskQueue,
+              taskRunner,
+              taskToolbox,
+              emitter
+          );
+
+          // Bootstrap task queue and task lockbox (load state stuff from the database)
+          taskQueue.bootstrap();
 
           // Sensible order to start stuff:
           final Lifecycle leaderLifecycle = new Lifecycle();
-          leaderLifecycle.addManagedInstance(queue);
-          leaderLifecycle.addManagedInstance(runner);
+          leaderLifecycle.addManagedInstance(taskQueue);
+          leaderLifecycle.addManagedInstance(taskRunner);
           Initialization.makeServiceDiscoveryClient(curator, serviceDiscoveryConfig, leaderLifecycle);
-          leaderLifecycle.addManagedInstance(consumer);
-          leaderLifecycle.start();
+          leaderLifecycle.addManagedInstance(taskConsumer);
 
           leading = true;
 
           try {
+            leaderLifecycle.start();
+
             while (leading) {
               mayBeStopped.await();
             }
-          } finally {
+          }
+          finally {
             log.info("Bowing out!");
             leaderLifecycle.stop();
           }
-        } catch(Exception e) {
+        }
+        catch (Exception e) {
           log.makeAlert(e, "Failed to lead").emit();
           throw Throwables.propagate(e);
-        } finally {
+        }
+        finally {
           giant.unlock();
         }
       }
@@ -181,4 +205,19 @@ public class TaskMaster
       throw Throwables.propagate(e);
     }
   }
+
+  public TaskRunner getTaskRunner()
+  {
+    return theRunner;
+  }
+
+  public TaskQueue getTaskQueue()
+  {
+    return taskQueue;
+  }
+
+  public TaskToolbox getTaskToolbox()
+  {
+    return taskToolbox;
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskQueue.java

@@ -19,75 +19,146 @@
 
 package com.metamx.druid.merger.coordinator;
 
-import com.google.common.base.Function;
 import com.google.common.base.Optional;
 import com.google.common.base.Preconditions;
-import com.google.common.base.Predicate;
-import com.google.common.collect.Iterables;
+import com.google.common.base.Throwables;
+import com.google.common.collect.ArrayListMultimap;
 import com.google.common.collect.Lists;
-import com.google.common.collect.Maps;
+import com.google.common.collect.Multimap;
 import com.google.common.collect.Ordering;
-import com.google.common.primitives.Booleans;
-import com.metamx.common.Pair;
-import com.metamx.common.guava.Comparators;
-import com.metamx.common.guava.FunctionalIterable;
 import com.metamx.common.lifecycle.LifecycleStart;
 import com.metamx.common.lifecycle.LifecycleStop;
-import com.metamx.common.logger.Logger;
-import com.metamx.druid.client.DataSegment;
 import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.task.Task;
-import org.joda.time.DateTime;
-import org.joda.time.Interval;
+import com.metamx.emitter.EmittingLogger;
 
-import javax.annotation.Nullable;
-import java.util.Collections;
 import java.util.List;
 import java.util.Map;
-import java.util.NavigableMap;
-import java.util.NavigableSet;
-import java.util.TreeMap;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * Interface between task producers and task consumers.
- *
+ * <p/>
  * The queue accepts tasks from producers using {@link #add} and delivers tasks to consumers using either
  * {@link #take} or {@link #poll}. Ordering is mostly-FIFO, with deviations when the natural next task would conflict
  * with a currently-running task. In that case, tasks are skipped until a runnable one is found.
- *
- * To manage locking, the queue keeps track of currently-running tasks as {@link TaskGroup} objects. The idea is that
- * only one TaskGroup can be running on a particular dataSource + interval, and that TaskGroup has a single version
- * string that all tasks in the group must use to publish segments. Tasks in the same TaskGroup may run concurrently.
- *
- * For persistence, the queue saves new tasks from {@link #add} and task status updates from {@link #done} using a
- * {@link TaskStorage} object.
- *
+ * <p/>
+ * To manage locking, the queue keeps track of currently-running tasks as {@link com.metamx.druid.merger.common.TaskLock} objects. The idea is that
+ * only one TaskLock can be running on a particular dataSource + interval, and that TaskLock has a single version
+ * string that all tasks in the group must use to publish segments. Tasks in the same TaskLock may run concurrently.
+ * <p/>
+ * For persistence, the queue saves new tasks from {@link #add} and task status updates from {@link #notify} using a
+ * {@link TaskStorage} obj
+ * <p/>
  * To support leader election of our containing system, the queue can be stopped (in which case it will not accept
  * any new tasks, or hand out any more tasks, until started again).
  */
 public class TaskQueue
 {
   private final List<Task> queue = Lists.newLinkedList();
-  private final Map<String, NavigableMap<Interval, TaskGroup>> running = Maps.newHashMap();
   private final TaskStorage taskStorage;
-
+  private final TaskLockbox taskLockbox;
   private final ReentrantLock giant = new ReentrantLock();
   private final Condition workMayBeAvailable = giant.newCondition();
 
   private volatile boolean active = false;
 
-  private static final Logger log = new Logger(TaskQueue.class);
+  private static final EmittingLogger log = new EmittingLogger(TaskQueue.class);
 
-  public TaskQueue(TaskStorage taskStorage)
+  public TaskQueue(TaskStorage taskStorage, TaskLockbox taskLockbox)
   {
     this.taskStorage = Preconditions.checkNotNull(taskStorage, "taskStorage");
+    this.taskLockbox = Preconditions.checkNotNull(taskLockbox, "taskLockbox");
   }
 
   /**
-   * Starts this task queue. Loads tasks from our task storage facility and allows {@link #add(Task)} to accept
-   * new tasks. This should not be called on an already-started queue.
+   * Bootstraps this task queue and associated task lockbox. Clears the lockbox before running. Should be called
+   * while the queue is stopped. It is not a good idea to start the queue if this method fails.
+   */
+  public void bootstrap()
+  {
+    giant.lock();
+
+    try {
+      Preconditions.checkState(!active, "queue must be stopped");
+
+      log.info("Bootstrapping queue (and associated lockbox)");
+
+      queue.clear();
+      taskLockbox.clear();
+
+      // Add running tasks to the queue
+      final List<Task> runningTasks = taskStorage.getRunningTasks();
+
+      for(final Task task : runningTasks) {
+        queue.add(task);
+      }
+
+      // Get all locks, along with which tasks they belong to
+      final Multimap<TaskLock, Task> tasksByLock = ArrayListMultimap.create();
+      for(final Task runningTask : runningTasks) {
+        for(final TaskLock taskLock : taskStorage.getLocks(runningTask.getId())) {
+          tasksByLock.put(taskLock, runningTask);
+        }
+      }
+
+      // Sort locks by version
+      final Ordering<TaskLock> byVersionOrdering = new Ordering<TaskLock>()
+      {
+        @Override
+        public int compare(TaskLock left, TaskLock right)
+        {
+          return left.getVersion().compareTo(right.getVersion());
+        }
+      };
+
+      // Acquire as many locks as possible, in version order
+      for(final Map.Entry<TaskLock, Task> taskAndLock : tasksByLock.entries()) {
+        final Task task = taskAndLock.getValue();
+        final TaskLock savedTaskLock = taskAndLock.getKey();
+
+        final Optional<TaskLock> acquiredTaskLock = taskLockbox.tryLock(
+            task,
+            savedTaskLock.getInterval(),
+            Optional.of(savedTaskLock.getVersion())
+        );
+
+        if(acquiredTaskLock.isPresent() && savedTaskLock.getVersion().equals(acquiredTaskLock.get().getVersion())) {
+          log.info(
+              "Reacquired lock on interval[%s] version[%s] for task: %s",
+              savedTaskLock.getInterval(),
+              savedTaskLock.getVersion(),
+              task.getId()
+          );
+        } else if(acquiredTaskLock.isPresent()) {
+          log.info(
+              "Could not reacquire lock on interval[%s] version[%s] (got version[%s] instead) for task: %s",
+              savedTaskLock.getInterval(),
+              savedTaskLock.getVersion(),
+              acquiredTaskLock.get().getVersion(),
+              task.getId()
+          );
+        } else {
+          log.info(
+              "Could not reacquire lock on interval[%s] version[%s] for task: %s",
+              savedTaskLock.getInterval(),
+              savedTaskLock.getVersion(),
+              task.getId()
+          );
+        }
+      }
+
+      log.info("Bootstrapped %,d tasks. Ready to go!", runningTasks.size());
+    } finally {
+      giant.unlock();
+    }
+  }
+
+  /**
+   * Starts this task queue. Allows {@link #add(Task)} to accept new tasks. This should not be called on
+   * an already-started queue.
    */
   @LifecycleStart
   public void start()
@@ -95,62 +166,9 @@ public class TaskQueue
     giant.lock();
 
     try {
-
-      Preconditions.checkState(!active, "queue was already started!");
-      Preconditions.checkState(queue.isEmpty(), "queue must be empty!");
-      Preconditions.checkState(running.isEmpty(), "running list must be empty!");
-
-      // XXX - We might want a TaskStorage API that does this, but including the Pair type in the interface seems clumsy.
-      final List<Pair<Task, String>> runningTasks = Lists.transform(
-          taskStorage.getRunningTasks(),
-          new Function<Task, Pair<Task, String>>()
-          {
-            @Override
-            public Pair<Task, String> apply(Task task)
-            {
-              return Pair.of(task, taskStorage.getVersion(task.getId()).orNull());
-            }
-          }
-      );
-
-      // Sort by version, with nulls last
-      final Ordering<Pair<Task, String>> byVersionOrdering = new Ordering<Pair<Task, String>>()
-      {
-        final private Ordering<String> baseOrdering = Ordering.natural().nullsLast();
-
-        @Override
-        public int compare(
-            Pair<Task, String> left, Pair<Task, String> right
-        )
-        {
-          return baseOrdering.compare(left.rhs, right.rhs);
-        }
-      };
-
-      for(final Pair<Task, String> taskAndVersion : byVersionOrdering.sortedCopy(runningTasks)) {
-        final Task task = taskAndVersion.lhs;
-        final String preferredVersion = taskAndVersion.rhs;
-
-        queue.add(task);
-
-        if(preferredVersion != null) {
-          final Optional<String> version = tryLock(task, Optional.of(preferredVersion));
-
-          log.info(
-              "Bootstrapped task[%s] with preferred version[%s]: %s",
-              task.getId(),
-              preferredVersion,
-              version.isPresent() ? String.format("locked with version[%s]", version.get()) : "not lockable"
-          );
-        } else {
-          log.info("Bootstrapped task[%s] with no preferred version", task.getId());
-        }
-      }
-
-      log.info("Bootstrapped %,d tasks. Ready to go!", runningTasks.size());
+      Preconditions.checkState(!active, "queue must be stopped");
 
       active = true;
-
       workMayBeAvailable.signalAll();
     }
     finally {
@@ -168,12 +186,12 @@ public class TaskQueue
     giant.lock();
 
     try {
-
+      log.info("Naptime! Shutting down until we are started again.");
       queue.clear();
-      running.clear();
+      taskLockbox.clear();
       active = false;
-
-    } finally {
+    }
+    finally {
       giant.unlock();
     }
   }
@@ -182,20 +200,35 @@ public class TaskQueue
    * Adds some work to the queue and the underlying task storage facility with a generic "running" status.
    *
    * @param task task to add
+   *
    * @return true
    */
-  public boolean add(Task task)
+  public boolean add(final Task task)
   {
     giant.lock();
 
     try {
       Preconditions.checkState(active, "Queue is not active!");
 
-      taskStorage.insert(task, TaskStatus.running(task.getId()));
+      // If this throws with any sort of exception, including TaskExistsException, we don't want to
+      // insert the task into our queue.
+      try {
+        taskStorage.insert(task, TaskStatus.running(task.getId()));
+      } catch(TaskExistsException e) {
+        log.warn("Attempt to add task twice: %s", task.getId());
+        throw Throwables.propagate(e);
+      }
 
       queue.add(task);
       workMayBeAvailable.signalAll();
 
+      // Attempt to add this task to a running task group. Silently continue if this is not possible.
+      // The main reason this is here is so when subtasks are added, they end up in the same task group
+      // as their parent whenever possible.
+      if(task.getFixedInterval().isPresent()) {
+        taskLockbox.tryLock(task, task.getFixedInterval().get());
+      }
+
       return true;
     }
     finally {
@@ -205,48 +238,58 @@ public class TaskQueue
 
   /**
    * Locks and returns next doable work from the queue. Blocks if there is no doable work.
+   *
    * @return runnable task
    */
-  public VersionedTaskWrapper take() throws InterruptedException
+  public Task take() throws InterruptedException
   {
     giant.lock();
 
     try {
-      VersionedTaskWrapper taskWrapper;
+      Task task;
 
-      while((taskWrapper = poll()) == null) {
-        log.info("Waiting for work...");
-        workMayBeAvailable.await();
+      log.info("Waiting for work...");
+
+      while ((task = poll()) == null) {
+        // awaitNanos because work may become available without this condition signalling,
+        // due to other folks messing with the taskLockbox
+        workMayBeAvailable.awaitNanos(1000000000L /* 1 second */);
       }
 
-      return taskWrapper;
-    } finally {
+      return task;
+    }
+    finally {
       giant.unlock();
     }
   }
 
   /**
    * Locks and removes next doable work from the queue. Returns null if there is no doable work.
+   *
    * @return runnable task or null
    */
-  public VersionedTaskWrapper poll()
+  public Task poll()
   {
     giant.lock();
 
     try {
-      log.info("Checking for doable work");
-      for(final Task task : queue) {
-        final Optional<String> maybeVersion = tryLock(task);
-        if(maybeVersion.isPresent()) {
-          Preconditions.checkState(active, "wtf? Found task when inactive");
-          taskStorage.setVersion(task.getId(), maybeVersion.get());
+      for (final Task task : queue) {
+        if(task.getFixedInterval().isPresent()) {
+          // If this task has a fixed interval, attempt to lock it right now.
+          final Optional<TaskLock> maybeLock = taskLockbox.tryLock(task, task.getFixedInterval().get());
+          if(maybeLock.isPresent()) {
+            log.info("Task claimed with fixed interval lock: %s", task.getId());
+            queue.remove(task);
+            return task;
+          }
+        } else {
+          // No fixed interval. Let's just run this and see what happens.
+          log.info("Task claimed with no fixed interval lock: %s", task.getId());
           queue.remove(task);
-          log.info("Task claimed: %s", task);
-          return new VersionedTaskWrapper(task, maybeVersion.get());
+          return task;
         }
       }
 
-      log.info("No doable work found.");
       return null;
     }
     finally {
@@ -255,312 +298,61 @@ public class TaskQueue
   }
 
   /**
-   * Unlock some work. Does not update the task storage facility. Throws an exception if this work is not currently
-   * running.
+   * Notify this queue that some task has an updated status. If this update is valid, the status will be persisted in
+   * the task storage facility. If the status is a completed status, the task will be unlocked and no further
+   * updates will be accepted.
    *
-   * @param task task to unlock
-   * @throws IllegalStateException if task is not currently locked
+   * @param task           task to update
+   * @param taskStatus new task status
+   *
+   * @throws NullPointerException     if task or status is null
+   * @throws IllegalArgumentException if the task ID does not match the status ID
+   * @throws IllegalStateException    if this queue is currently shut down
    */
-  private void unlock(final Task task)
-  {
-    giant.lock();
-
-    try {
-      final String dataSource = task.getDataSource();
-      final Interval interval = task.getInterval();
-
-      final List<TaskGroup> maybeTaskGroup = Lists.newArrayList(
-          FunctionalIterable.create(findLocks(dataSource, interval))
-                            .filter(
-                                new Predicate<TaskGroup>()
-                                {
-                                  @Override
-                                  public boolean apply(TaskGroup taskGroup)
-                                  {
-                                    return taskGroup.getTaskSet().contains(task);
-                                  }
-                                }
-                            )
-      );
-
-      final TaskGroup taskGroup;
-      if(maybeTaskGroup.size() == 1) {
-        taskGroup = maybeTaskGroup.get(0);
-      } else {
-        throw new IllegalStateException(String.format("Task must be running: %s", task.getId()));
-      }
-
-      // Remove task from live list
-      log.info("Removing task[%s] from TaskGroup[%s]", task.getId(), taskGroup.getGroupId());
-      taskGroup.getTaskSet().remove(task);
-
-      if(taskGroup.getTaskSet().size() == 0) {
-        log.info("TaskGroup complete: %s", taskGroup);
-        running.get(dataSource).remove(taskGroup.getInterval());
-      }
-
-      if(running.get(dataSource).size() == 0) {
-        running.remove(dataSource);
-      }
-
-      workMayBeAvailable.signalAll();
-    }
-    finally {
-      giant.unlock();
-    }
-  }
-
-  /**
-   * Unlock some task and update its status in the task storage facility. If "status" is a continuation status (i.e.
-   * it has nextTasks) this will add the next tasks to the queue with a generic running status.
-   *
-   * @param task task to unlock
-   * @param status task completion status; must not be runnable
-   * @throws IllegalStateException if task is not currently running, or if status is runnable
-   */
-  public void done(final Task task, final TaskStatus status)
+  public void notify(final Task task, final TaskStatus taskStatus)
   {
     giant.lock();
 
     try {
+      Preconditions.checkNotNull(task, "task");
+      Preconditions.checkNotNull(taskStatus, "status");
       Preconditions.checkState(active, "Queue is not active!");
-      Preconditions.checkState(!status.isRunnable(), "status must no longer be runnable");
-
-      Preconditions.checkState(
-          task.getId().equals(status.getId()),
+      Preconditions.checkArgument(
+          task.getId().equals(taskStatus.getId()),
           "Mismatching task ids[%s/%s]",
           task.getId(),
-          status.getId()
+          taskStatus.getId()
       );
 
-      // Might change on continuation failure
-      TaskStatus actualStatus = status;
-
-      // Add next tasks, if any
+      // Save status to DB
+      boolean didPersistStatus = false;
       try {
-        for(final Task nextTask : status.getNextTasks()) {
-          add(nextTask);
-          tryLock(nextTask);
+        final Optional<TaskStatus> previousStatus = taskStorage.getStatus(task.getId());
+        if (!previousStatus.isPresent() || !previousStatus.get().isRunnable()) {
+          log.makeAlert("Ignoring notification for dead task").addData("task", task.getId()).emit();
+          return;
+        } else {
+          taskStorage.setStatus(taskStatus);
+          didPersistStatus = true;
         }
       } catch(Exception e) {
-        log.error(e, "Failed to continue task: %s", task.getId());
-        actualStatus = TaskStatus.failure(task.getId());
+        log.makeAlert(e, "Failed to persist status for task")
+           .addData("task", task.getId())
+           .addData("statusCode", taskStatus.getStatusCode())
+           .emit();
       }
 
-      unlock(task);
-
-      // Update status in DB
-      taskStorage.setStatus(task.getId(), actualStatus);
-
-      log.info("Task done: %s", task);
-    }
-    finally {
-      giant.unlock();
-    }
-  }
-
-  /**
-   * Returns task status for a particular task ID. May collapse "continued" statuses down to "success" or "failure"
-   * if appropriate.
-   */
-  public Optional<TaskStatus> getStatus(final String taskid)
-  {
-    giant.lock();
-
-    try {
-      final Optional<TaskStatus> statusOptional = taskStorage.getStatus(taskid);
-      if(statusOptional.isPresent()) {
-        // See if we can collapse this down
-        return Optional.of(collapseStatus(statusOptional.get()));
-      } else {
-        return statusOptional;
-      }
-    }
-    finally {
-      giant.unlock();
-    }
-  }
-
-  private TaskStatus collapseStatus(TaskStatus status)
-  {
-
-    if (status.isContinued()) {
-
-      int nSubtasks = 0;
-      int nSuccesses = 0;
-      List<DataSegment> segments = Lists.newArrayList();
-
-      for(final Task subtask : status.getNextTasks()) {
-
-        final TaskStatus subtaskStatus = collapseStatus(taskStorage.getStatus(subtask.getId()).get());
-        nSubtasks ++;
-
-        if (subtaskStatus.isFailure()) {
-          return TaskStatus.failure(status.getId());
-        } else if (subtaskStatus.isSuccess()) {
-          nSuccesses++;
-          segments.addAll(subtaskStatus.getSegments());
-        }
-
-      }
-
-      if (nSubtasks == nSuccesses) {
-        return TaskStatus.success(status.getId(), segments);
-      }
-
-    }
-
-    // unable to collapse it down
-    return status;
-
-  }
-
-  /**
-   * Attempt to lock a task, without removing it from the queue. Can safely be called multiple times on the same task.
-   *
-   * @param task task to attempt to lock
-   * @return lock version if lock was acquired, absent otherwise
-   */
-  private Optional<String> tryLock(final Task task)
-  {
-    return tryLock(task, Optional.<String>absent());
-  }
-
-  /**
-   * Attempt to lock a task, without removing it from the queue. Can safely be called multiple times on the same task.
-   *
-   * @param task task to attempt to lock
-   * @param preferredVersion use this version if possible (no guarantees, though!)
-   * @return lock version if lock was acquired, absent otherwise
-   */
-  private Optional<String> tryLock(final Task task, final Optional<String> preferredVersion)
-  {
-    giant.lock();
-
-    try {
-
-      final String dataSource = task.getDataSource();
-      final Interval interval = task.getInterval();
-
-      final List<TaskGroup> foundLocks = findLocks(dataSource, interval);
-      final TaskGroup taskGroupToUse;
-
-      if (foundLocks.size() > 1) {
-
-        // Too many existing locks.
-        return Optional.absent();
-
-      } else if (foundLocks.size() == 1) {
-
-        // One existing lock -- check if we can add to it.
-
-        final TaskGroup foundLock = Iterables.getOnlyElement(foundLocks);
-        if (foundLock.getInterval().contains(interval) && foundLock.getGroupId().equals(task.getGroupId())) {
-          taskGroupToUse = foundLock;
+      if(taskStatus.isComplete()) {
+        if(didPersistStatus) {
+          log.info("Task done: %s", task);
+          taskLockbox.unlock(task);
+          workMayBeAvailable.signalAll();
         } else {
-          return Optional.absent();
+          // TODO: This could be a task-status-submission retry queue instead of retrying the entire task,
+          // TODO: which is heavy and probably not necessary.
+          log.warn("Status could not be persisted! Reinserting task: %s", task.getId());
+          queue.add(task);
         }
-
-      } else {
-
-        // No existing locks. We can make a new one.
-        if (!running.containsKey(dataSource)) {
-          running.put(dataSource, new TreeMap<Interval, TaskGroup>(Comparators.intervalsByStartThenEnd()));
-        }
-
-        // Create new TaskGroup and assign it a version.
-        // Assumption: We'll choose a version that is greater than any previously-chosen version for our interval. (This
-        // may not always be true, unfortunately. See below.)
-
-        final String version;
-
-        if(preferredVersion.isPresent()) {
-          // We have a preferred version. Since this is a private method, we'll trust our caller to not break our
-          // ordering assumptions and just use it.
-          version = preferredVersion.get();
-        } else {
-          // We are running under an interval lock right now, so just using the current time works as long as we can trust
-          // our clock to be monotonic and have enough resolution since the last time we created a TaskGroup for the same
-          // interval. This may not always be true; to assure it we would need to use some method of timekeeping other
-          // than the wall clock.
-          version = new DateTime().toString();
-        }
-
-        taskGroupToUse = new TaskGroup(task.getGroupId(), dataSource, interval, version);
-        running.get(dataSource)
-               .put(interval, taskGroupToUse);
-
-        log.info("Created new TaskGroup[%s]", taskGroupToUse);
-
-      }
-
-      // Add to existing TaskGroup, if necessary
-      if (taskGroupToUse.getTaskSet().add(task)) {
-        log.info("Added task[%s] to TaskGroup[%s]", task.getId(), taskGroupToUse.getGroupId());
-      } else {
-        log.info("Task[%s] already present in TaskGroup[%s]", task.getId(), taskGroupToUse.getGroupId());
-      }
-
-      return Optional.of(taskGroupToUse.getVersion());
-
-    } finally {
-      giant.unlock();
-    }
-
-  }
-
-  /**
-   * Return all locks that overlap some search interval.
-   */
-  private List<TaskGroup> findLocks(final String dataSource, final Interval interval)
-  {
-    giant.lock();
-
-    try {
-      final NavigableMap<Interval, TaskGroup> dsRunning = running.get(dataSource);
-      if(dsRunning == null) {
-        // No locks at all
-        return Collections.emptyList();
-      } else {
-        // Tasks are indexed by locked interval, which are sorted by interval start. Intervals are non-overlapping, so:
-        final NavigableSet<Interval> dsLockbox = dsRunning.navigableKeySet();
-        final Iterable<Interval> searchIntervals = Iterables.concat(
-            // Single interval that starts at or before ours
-            Collections.singletonList(dsLockbox.floor(new Interval(interval.getStart(), new DateTime(Long.MAX_VALUE)))),
-
-            // All intervals that start somewhere between our start instant (exclusive) and end instant (exclusive)
-            dsLockbox.subSet(
-                new Interval(interval.getStart(), new DateTime(Long.MAX_VALUE)),
-                false,
-                new Interval(interval.getEnd(), interval.getEnd()),
-                false
-            )
-        );
-
-        return Lists.newArrayList(
-            FunctionalIterable
-                .create(searchIntervals)
-                .filter(
-                    new Predicate<Interval>()
-                    {
-                      @Override
-                      public boolean apply(@Nullable Interval searchInterval)
-                      {
-                        return searchInterval != null && searchInterval.overlaps(interval);
-                      }
-                    }
-                )
-                .transform(
-                    new Function<Interval, TaskGroup>()
-                    {
-                      @Override
-                      public TaskGroup apply(Interval interval)
-                      {
-                        return dsRunning.get(interval);
-                      }
-                    }
-                )
-        );
       }
     }
     finally {

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskRunner.java

@@ -19,20 +19,29 @@
 
 package com.metamx.druid.merger.coordinator;
 
+import com.metamx.druid.merger.common.TaskCallback;
 import com.metamx.druid.merger.common.task.Task;
 
+import java.util.Collection;
+
 /**
- * Interface for handing off tasks. Used by a {@link com.metamx.druid.merger.coordinator.exec.TaskConsumer} to run tasks that
- * have been locked.
+ * Interface for handing off tasks. Used by a {@link com.metamx.druid.merger.coordinator.exec.TaskConsumer} to
+ * run tasks that have been locked.
  */
 public interface TaskRunner
 {
   /**
-   * Run a task with a particular context and call a callback. The callback should be called exactly once.
+   * Run a task with a particular context and call a callback. The callback may be called multiple times with RUNNING
+   * status, but should be called exactly once with a non-RUNNING status (e.g. SUCCESS, FAILED, CONTINUED...).
    *
    * @param task task to run
-   * @param context task context to run under
    * @param callback callback to be called exactly once
    */
-  public void run(Task task, TaskContext context, TaskCallback callback);
+  public void run(Task task, TaskCallback callback);
+
+  public Collection<TaskRunnerWorkItem> getRunningTasks();
+
+  public Collection<TaskRunnerWorkItem> getPendingTasks();
+
+  public Collection<ZkWorker> getWorkers();
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskRunnerWorkItem.java

@@ -0,0 +1,133 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator;
+
+import com.metamx.druid.merger.common.TaskCallback;
+import com.metamx.druid.merger.common.task.Task;
+import org.joda.time.DateTime;
+import org.joda.time.DateTimeComparator;
+
+/**
+ * A holder for a task and different components associated with the task
+ */
+public class TaskRunnerWorkItem implements Comparable<TaskRunnerWorkItem>
+{
+  private final Task task;
+  private final TaskCallback callback;
+  private final RetryPolicy retryPolicy;
+  private final DateTime createdTime;
+
+  private volatile DateTime queueInsertionTime;
+
+  public TaskRunnerWorkItem(
+      Task task,
+      TaskCallback callback,
+      RetryPolicy retryPolicy,
+      DateTime createdTime
+  )
+  {
+    this.task = task;
+    this.callback = callback;
+    this.retryPolicy = retryPolicy;
+    this.createdTime = createdTime;
+  }
+
+  public Task getTask()
+  {
+    return task;
+  }
+
+  public TaskCallback getCallback()
+  {
+    return callback;
+  }
+
+  public RetryPolicy getRetryPolicy()
+  {
+    return retryPolicy;
+  }
+
+  public DateTime getCreatedTime()
+  {
+    return createdTime;
+  }
+
+  public DateTime getQueueInsertionTime()
+  {
+    return queueInsertionTime;
+  }
+
+  public TaskRunnerWorkItem withQueueInsertionTime(DateTime time)
+  {
+    this.queueInsertionTime = time;
+    return this;
+  }
+
+  @Override
+  public int compareTo(TaskRunnerWorkItem taskRunnerWorkItem)
+  {
+    return DateTimeComparator.getInstance().compare(createdTime, taskRunnerWorkItem.getCreatedTime());
+  }
+
+  @Override
+  public boolean equals(Object o)
+  {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+
+    TaskRunnerWorkItem that = (TaskRunnerWorkItem) o;
+
+    if (callback != null ? !callback.equals(that.callback) : that.callback != null) {
+      return false;
+    }
+    if (retryPolicy != null ? !retryPolicy.equals(that.retryPolicy) : that.retryPolicy != null) {
+      return false;
+    }
+    if (task != null ? !task.equals(that.task) : that.task != null) {
+      return false;
+    }
+
+    return true;
+  }
+
+  @Override
+  public int hashCode()
+  {
+    int result = task != null ? task.hashCode() : 0;
+    result = 31 * result + (callback != null ? callback.hashCode() : 0);
+    result = 31 * result + (retryPolicy != null ? retryPolicy.hashCode() : 0);
+    return result;
+  }
+
+  @Override
+  public String toString()
+  {
+    return "TaskRunnerWorkItem{" +
+           "task=" + task +
+           ", callback=" + callback +
+           ", retryPolicy=" + retryPolicy +
+           ", createdTime=" + createdTime +
+           '}';
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskRunnerWorkQueue.java

@@ -19,26 +19,17 @@
 
 package com.metamx.druid.merger.coordinator;
 
-import com.metamx.druid.merger.common.task.Task;
+import org.joda.time.DateTime;
 
-public class VersionedTaskWrapper
+import java.util.concurrent.ConcurrentSkipListMap;
+
+/**
+ */
+public class TaskRunnerWorkQueue extends ConcurrentSkipListMap<String, TaskRunnerWorkItem>
 {
-  final Task task;
-  final String version;
-
-  public VersionedTaskWrapper(Task task, String version)
+  @Override
+  public TaskRunnerWorkItem put(String s, TaskRunnerWorkItem taskRunnerWorkItem)
   {
-    this.task = task;
-    this.version = version;
-  }
-
-  public Task getTask()
-  {
-    return task;
-  }
-
-  public String getVersion()
-  {
-    return version;
+    return super.put(s, taskRunnerWorkItem.withQueueInsertionTime(new DateTime()));
   }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskStorage.java

@@ -21,6 +21,8 @@ package com.metamx.druid.merger.coordinator;
 
 import com.google.common.base.Optional;
 import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.actions.TaskAction;
+import com.metamx.druid.merger.common.TaskLock;
 import com.metamx.druid.merger.common.task.Task;
 
 import java.util.List;
@@ -29,20 +31,34 @@ public interface TaskStorage
 {
   /**
    * Adds a task to the storage facility with a particular status. If the task ID already exists, this method
-   * will throw an exception.
+   * will throw a {@link TaskExistsException}.
    */
   public void insert(Task task, TaskStatus status);
 
   /**
-   * Updates task status in the storage facility.
+   * Persists task status in the storage facility. This method should throw an exception if the task status lifecycle
+   * is not respected (absent -> RUNNING -> SUCCESS/FAILURE).
    */
-  public void setStatus(String taskid, TaskStatus status);
+  public void setStatus(TaskStatus status);
 
   /**
-   * Updates task version in the storage facility. If the task already has a version, this method will throw
-   * an exception.
+   * Persists lock state in the storage facility.
    */
-  public void setVersion(String taskid, String version);
+  public void addLock(String taskid, TaskLock taskLock);
+
+  /**
+   * Removes lock state from the storage facility. It is harmless to keep old locks in the storage facility, but
+   * this method can help reclaim wasted space.
+   */
+  public void removeLock(String taskid, TaskLock taskLock);
+
+  /**
+   * Returns task as stored in the storage facility. If the task ID does not exist, this will return an
+   * absentee Optional.
+   *
+   * TODO -- This method probably wants to be combined with {@link #getStatus}.
+   */
+  public Optional<Task> getTask(String taskid);
 
   /**
    * Returns task status as stored in the storage facility. If the task ID does not exist, this will return
@@ -51,13 +67,22 @@ public interface TaskStorage
   public Optional<TaskStatus> getStatus(String taskid);
 
   /**
-   * Returns task version as stored in the storage facility. If the task ID does not exist, or if the task ID exists
-   * but was not yet assigned a version, this will return an absentee Optional.
+   * Add an action taken by a task to the audit log.
    */
-  public Optional<String> getVersion(String taskid);
+  public <T> void addAuditLog(TaskAction<T> taskAction);
+
+  /**
+   * Returns all actions taken by a task.
+   */
+  public List<TaskAction> getAuditLogs(String taskid);
 
   /**
    * Returns a list of currently-running tasks as stored in the storage facility, in no particular order.
    */
   public List<Task> getRunningTasks();
+
+  /**
+   * Returns a list of locks for a particular task.
+   */
+  public List<TaskLock> getLocks(String taskid);
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskStorageQueryAdapter.java

@@ -0,0 +1,177 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator;
+
+import com.google.common.base.Function;
+import com.google.common.base.Optional;
+import com.google.common.base.Predicate;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import com.metamx.common.guava.FunctionalIterable;
+import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.actions.SegmentInsertAction;
+import com.metamx.druid.merger.common.actions.SpawnTasksAction;
+import com.metamx.druid.merger.common.actions.TaskAction;
+import com.metamx.druid.merger.common.task.Task;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Wraps a {@link TaskStorage}, providing a useful collection of read-only methods.
+ */
+public class TaskStorageQueryAdapter
+{
+  private final TaskStorage storage;
+
+  public TaskStorageQueryAdapter(TaskStorage storage)
+  {
+    this.storage = storage;
+  }
+
+  public Optional<TaskStatus> getStatus(final String taskid)
+  {
+    return storage.getStatus(taskid);
+  }
+
+  /**
+   * Returns all recursive task statuses for a particular task, staying within the same task group. Includes that
+   * task, plus any tasks it spawned, and so on. Does not include spawned tasks that ended up in a different task
+   * group. Does not include this task's parents or siblings.
+   */
+  public Map<String, Optional<TaskStatus>> getSameGroupChildStatuses(final String taskid)
+  {
+    final Optional<Task> taskOptional = storage.getTask(taskid);
+    final Optional<TaskStatus> statusOptional = storage.getStatus(taskid);
+    final ImmutableMap.Builder<String, Optional<TaskStatus>> resultBuilder = ImmutableMap.builder();
+
+    resultBuilder.put(taskid, statusOptional);
+
+    final Iterable<Task> nextTasks = FunctionalIterable
+        .create(storage.getAuditLogs(taskid)).filter(
+            new Predicate<TaskAction>()
+            {
+              @Override
+              public boolean apply(TaskAction taskAction)
+              {
+                return taskAction instanceof SpawnTasksAction;
+              }
+            }
+        ).transformCat(
+            new Function<TaskAction, Iterable<Task>>()
+            {
+              @Override
+              public Iterable<Task> apply(TaskAction taskAction)
+              {
+                return ((SpawnTasksAction) taskAction).getNewTasks();
+              }
+            }
+        );
+
+    if(taskOptional.isPresent() && statusOptional.isPresent()) {
+      for(final Task nextTask : nextTasks) {
+        if(nextTask.getGroupId().equals(taskOptional.get().getGroupId())) {
+          resultBuilder.putAll(getSameGroupChildStatuses(nextTask.getId()));
+        }
+      }
+    }
+
+    return resultBuilder.build();
+  }
+
+  /**
+   * Like {@link #getSameGroupChildStatuses}, but flattens the recursive statuses into a single, merged status.
+   */
+  public Optional<TaskStatus> getSameGroupMergedStatus(final String taskid)
+  {
+    final Map<String, Optional<TaskStatus>> statuses = getSameGroupChildStatuses(taskid);
+
+    int nSuccesses = 0;
+    int nFailures = 0;
+    int nTotal = 0;
+
+    for(final Optional<TaskStatus> statusOption : statuses.values()) {
+      nTotal ++;
+
+      if(statusOption.isPresent()) {
+        final TaskStatus status = statusOption.get();
+
+        if(status.isSuccess()) {
+          nSuccesses ++;
+        } else if(status.isFailure()) {
+          nFailures ++;
+        }
+      }
+    }
+
+    final Optional<TaskStatus> status;
+
+    if(nTotal == 0) {
+      status = Optional.absent();
+    } else if(nSuccesses == nTotal) {
+      status = Optional.of(TaskStatus.success(taskid));
+    } else if(nFailures > 0) {
+      status = Optional.of(TaskStatus.failure(taskid));
+    } else {
+      status = Optional.of(TaskStatus.running(taskid));
+    }
+
+    return status;
+  }
+
+  /**
+   * Returns all segments created by descendants for a particular task that stayed within the same task group. Includes
+   * that task, plus any tasks it spawned, and so on. Does not include spawned tasks that ended up in a different task
+   * group. Does not include this task's parents or siblings.
+   */
+  public Set<DataSegment> getSameGroupNewSegments(final String taskid)
+  {
+    // TODO: This is useful for regular index tasks (so we know what was published), but
+    // TODO: for long-lived index tasks the list can get out of hand. We may want a limit.
+
+    final Optional<Task> taskOptional = storage.getTask(taskid);
+    final Set<DataSegment> segments = Sets.newHashSet();
+    final List<Task> nextTasks = Lists.newArrayList();
+
+    for(final TaskAction action : storage.getAuditLogs(taskid)) {
+      if(action instanceof SpawnTasksAction) {
+        nextTasks.addAll(((SpawnTasksAction) action).getNewTasks());
+      }
+
+      if(action instanceof SegmentInsertAction) {
+        segments.addAll(((SegmentInsertAction) action).getSegments());
+      }
+    }
+
+    if(taskOptional.isPresent()) {
+      for(final Task nextTask : nextTasks) {
+        if(nextTask.getGroupId().equals(taskOptional.get().getGroupId())) {
+          segments.addAll(getSameGroupNewSegments(nextTask.getId()));
+        }
+      }
+    }
+
+    return segments;
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/TaskWrapper.java

@@ -1,60 +0,0 @@
-/*
- * Druid - a distributed column store.
- * Copyright (C) 2012  Metamarkets Group Inc.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
- */
-
-package com.metamx.druid.merger.coordinator;
-
-import com.metamx.druid.merger.common.task.Task;
-
-/**
- */
-public class TaskWrapper
-{
-  private final Task task;
-  private final TaskContext taskContext;
-  private final TaskCallback callback;
-  private final RetryPolicy retryPolicy;
-
-  public TaskWrapper(Task task, TaskContext taskContext, TaskCallback callback, RetryPolicy retryPolicy)
-  {
-    this.task = task;
-    this.taskContext = taskContext;
-    this.callback = callback;
-    this.retryPolicy = retryPolicy;
-  }
-
-  public Task getTask()
-  {
-    return task;
-  }
-
-  public TaskContext getTaskContext()
-  {
-    return taskContext;
-  }
-
-  public TaskCallback getCallback()
-  {
-    return callback;
-  }
-
-  public RetryPolicy getRetryPolicy()
-  {
-    return retryPolicy;
-  }
-}

merger/src/main/java/com/metamx/druid/merger/coordinator/ZkWorker.java

@@ -37,8 +37,9 @@ import java.io.IOException;
 import java.util.Set;
 
 /**
+ * Holds information about a worker and a listener for task status changes associated with the worker.
  */
-public class WorkerWrapper implements Closeable
+public class ZkWorker implements Closeable
 {
   private final Worker worker;
   private final PathChildrenCache statusCache;
@@ -46,7 +47,7 @@ public class WorkerWrapper implements Closeable
 
   private volatile DateTime lastCompletedTaskTime = new DateTime();
 
-  public WorkerWrapper(Worker worker, PathChildrenCache statusCache, final ObjectMapper jsonMapper)
+  public ZkWorker(Worker worker, PathChildrenCache statusCache, final ObjectMapper jsonMapper)
   {
     this.worker = worker;
     this.statusCache = statusCache;
@@ -105,4 +106,15 @@ public class WorkerWrapper implements Closeable
   {
     statusCache.close();
   }
+
+  @Override
+  public String toString()
+  {
+    return "ZkWorker{" +
+           "worker=" + worker +
+           ", statusCache=" + statusCache +
+           ", cacheConverter=" + cacheConverter +
+           ", lastCompletedTaskTime=" + lastCompletedTaskTime +
+           '}';
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/config/IndexerCoordinatorConfig.java

@@ -52,9 +52,6 @@ public abstract class IndexerCoordinatorConfig
   @Default("local")
   public abstract String getStorageImpl();
 
-  @Config("druid.merger.taskDir")
-  public abstract File getBaseTaskDir();
-
   @Config("druid.merger.whitelist.enabled")
   @Default("false")
   public abstract boolean isWhitelistEnabled();
@@ -63,10 +60,6 @@ public abstract class IndexerCoordinatorConfig
   @Default("")
   public abstract String getWhitelistDatasourcesString();
 
-  public File getTaskDir(final Task task) {
-    return new File(getBaseTaskDir(), task.getId());
-  }
-
   public Set<String> getWhitelistDatasources()
   {
     if(whitelistDatasources == null) {
@@ -80,10 +73,6 @@ public abstract class IndexerCoordinatorConfig
     return whitelistDatasources;
   }
 
-  @Config("druid.merger.rowFlushBoundary")
-  @Default("500000")
-  public abstract long getRowFlushBoundary();
-
   @Config("druid.indexer.strategy")
   @Default("noop")
   public abstract String getStrategyImpl();

merger/src/main/java/com/metamx/druid/merger/coordinator/config/IndexerDbConnectorConfig.java

@@ -29,4 +29,12 @@ public abstract class IndexerDbConnectorConfig extends DbConnectorConfig
   @JsonProperty("taskTable")
   @Config("druid.database.taskTable")
   public abstract String getTaskTable();
+
+  @JsonProperty("taskLockTable")
+  @Config("druid.database.taskLockTable")
+  public abstract String getTaskLockTable();
+
+  @JsonProperty("taskLogTable")
+  @Config("druid.database.taskLogTable")
+  public abstract String getTaskLogTable();
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/config/RemoteTaskRunnerConfig.java

@@ -20,7 +20,6 @@
 package com.metamx.druid.merger.coordinator.config;
 
 import com.metamx.druid.merger.common.config.IndexerZkConfig;
-import org.joda.time.DateTime;
 import org.joda.time.Duration;
 import org.skife.config.Config;
 import org.skife.config.Default;
@@ -29,22 +28,6 @@ import org.skife.config.Default;
  */
 public abstract class RemoteTaskRunnerConfig extends IndexerZkConfig
 {
-  @Config("druid.indexer.terminateResources.duration")
-  @Default("PT1H")
-  public abstract Duration getTerminateResourcesDuration();
-
-  @Config("druid.indexer.terminateResources.originDateTime")
-  @Default("2012-01-01T00:55:00.000Z")
-  public abstract DateTime getTerminateResourcesOriginDateTime();
-
-  @Config("druid.indexer.maxWorkerIdleTimeMillisBeforeDeletion")
-  @Default("600000")
-  public abstract int getMaxWorkerIdleTimeMillisBeforeDeletion();
-
-  @Config("druid.indexer.maxScalingDuration")
-  @Default("PT1H")
-  public abstract Duration getMaxScalingDuration();
-
   @Config("druid.indexer.taskAssignmentTimeoutDuration")
   @Default("PT5M")
   public abstract Duration getTaskAssignmentTimeoutDuration();

merger/src/main/java/com/metamx/druid/merger/coordinator/exec/TaskConsumer.java

@@ -20,18 +20,14 @@
 package com.metamx.druid.merger.coordinator.exec;
 
 import com.google.common.base.Throwables;
-import com.google.common.collect.ImmutableSet;
 import com.metamx.common.lifecycle.LifecycleStart;
 import com.metamx.common.lifecycle.LifecycleStop;
-import com.metamx.druid.client.DataSegment;
+import com.metamx.druid.merger.common.TaskCallback;
 import com.metamx.druid.merger.common.TaskStatus;
+import com.metamx.druid.merger.common.TaskToolbox;
 import com.metamx.druid.merger.common.task.Task;
-import com.metamx.druid.merger.coordinator.MergerDBCoordinator;
-import com.metamx.druid.merger.coordinator.TaskCallback;
-import com.metamx.druid.merger.coordinator.TaskContext;
 import com.metamx.druid.merger.coordinator.TaskQueue;
 import com.metamx.druid.merger.coordinator.TaskRunner;
-import com.metamx.druid.merger.coordinator.VersionedTaskWrapper;
 import com.metamx.emitter.EmittingLogger;
 import com.metamx.emitter.service.ServiceEmitter;
 import com.metamx.emitter.service.ServiceMetricEvent;
@@ -40,7 +36,7 @@ public class TaskConsumer implements Runnable
 {
   private final TaskQueue queue;
   private final TaskRunner runner;
-  private final MergerDBCoordinator mergerDBCoordinator;
+  private final TaskToolbox toolbox;
   private final ServiceEmitter emitter;
   private final Thread thready;
 
@@ -51,13 +47,13 @@ public class TaskConsumer implements Runnable
   public TaskConsumer(
       TaskQueue queue,
       TaskRunner runner,
-      MergerDBCoordinator mergerDBCoordinator,
+      TaskToolbox toolbox,
       ServiceEmitter emitter
   )
   {
     this.queue = queue;
     this.runner = runner;
-    this.mergerDBCoordinator = mergerDBCoordinator;
+    this.toolbox = toolbox;
     this.emitter = emitter;
     this.thready = new Thread(this);
   }
@@ -83,176 +79,111 @@ public class TaskConsumer implements Runnable
       while (!Thread.currentThread().isInterrupted()) {
 
         final Task task;
-        final String version;
 
         try {
-          final VersionedTaskWrapper taskWrapper = queue.take();
-          task = taskWrapper.getTask();
-          version = taskWrapper.getVersion();
+          task = queue.take();
         }
         catch (InterruptedException e) {
           log.info(e, "Interrupted while waiting for new work");
-          throw Throwables.propagate(e);
+          throw e;
         }
 
         try {
-          handoff(task, version);
+          handoff(task);
         }
         catch (Exception e) {
           log.makeAlert(e, "Failed to hand off task")
              .addData("task", task.getId())
-             .addData("type", task.getType().toString())
+             .addData("type", task.getType())
              .addData("dataSource", task.getDataSource())
-             .addData("interval", task.getInterval())
+             .addData("interval", task.getFixedInterval())
              .emit();
 
-          // Retry would be nice, but only after we have a way to throttle and limit them.  Just fail for now.
-          if(!shutdown) {
-            queue.done(task, TaskStatus.failure(task.getId()));
+          // Retry would be nice, but only after we have a way to throttle and limit them. Just fail for now.
+          if (!shutdown) {
+            queue.notify(task, TaskStatus.failure(task.getId()));
           }
         }
       }
     }
-    catch (Throwable t) {
+    catch (Exception e) {
       // exit thread
-      log.error(t, "Uncaught Throwable while consuming tasks");
-      throw Throwables.propagate(t);
+      log.error(e, "Uncaught exception while consuming tasks");
+      throw Throwables.propagate(e);
     }
   }
 
-  private void handoff(final Task task, final String version) throws Exception
+  private void handoff(final Task task) throws Exception
   {
-    final TaskContext context = new TaskContext(
-        version,
-        ImmutableSet.copyOf(
-            mergerDBCoordinator.getSegmentsForInterval(
-                task.getDataSource(),
-                task.getInterval()
-            )
-        )
-    );
-    final ServiceMetricEvent.Builder builder = new ServiceMetricEvent.Builder()
+    final ServiceMetricEvent.Builder metricBuilder = new ServiceMetricEvent.Builder()
         .setUser2(task.getDataSource())
-        .setUser4(task.getType().toString())
-        .setUser5(task.getInterval().toString());
+        .setUser4(task.getType())
+        .setUser5(task.getFixedInterval().toString());
 
     // Run preflight checks
     TaskStatus preflightStatus;
     try {
-      preflightStatus = task.preflight(context);
+      preflightStatus = task.preflight(toolbox);
       log.info("Preflight done for task: %s", task.getId());
-    } catch(Exception e) {
+    }
+    catch (Exception e) {
       preflightStatus = TaskStatus.failure(task.getId());
       log.error(e, "Exception thrown during preflight for task: %s", task.getId());
     }
 
     if (!preflightStatus.isRunnable()) {
       log.info("Task finished during preflight: %s", task.getId());
-      queue.done(task, preflightStatus);
+      queue.notify(task, preflightStatus);
       return;
     }
 
-    // Hand off work to TaskRunner
+    // Hand off work to TaskRunner, with a callback
     runner.run(
-        task, context, new TaskCallback()
+        task, new TaskCallback()
     {
       @Override
       public void notify(final TaskStatus statusFromRunner)
       {
-
-        // task is done
-        log.info("TaskRunner finished task: %s", task);
-
-        // we might need to change this due to exceptions
-        TaskStatus status = statusFromRunner;
-
-        // If we're not supposed to be running anymore, don't do anything. Somewhat racey if the flag gets set after
-        // we check and before we commit the database transaction, but better than nothing.
-        if(shutdown) {
-          log.info("Abandoning task due to shutdown: %s", task.getId());
-          return;
-        }
-
-        // Publish returned segments
-        // FIXME: Publish in transaction
         try {
-          for (DataSegment segment : status.getSegments()) {
-            if (!task.getDataSource().equals(segment.getDataSource())) {
-              throw new IllegalStateException(
-                  String.format(
-                      "Segment for task[%s] has invalid dataSource: %s",
-                      task.getId(),
-                      segment.getIdentifier()
-                  )
-              );
+          log.info("Received %s status for task: %s", statusFromRunner.getStatusCode(), task);
+
+          // If we're not supposed to be running anymore, don't do anything. Somewhat racey if the flag gets set after
+          // we check and before we commit the database transaction, but better than nothing.
+          if (shutdown) {
+            log.info("Abandoning task due to shutdown: %s", task.getId());
+            return;
+          }
+
+          queue.notify(task, statusFromRunner);
+
+          // Emit event and log, if the task is done
+          if (statusFromRunner.isComplete()) {
+            metricBuilder.setUser3(statusFromRunner.getStatusCode().toString());
+            emitter.emit(metricBuilder.build("indexer/time/run/millis", statusFromRunner.getDuration()));
+
+            if (statusFromRunner.isFailure()) {
+              log.makeAlert("Failed to index")
+                 .addData("task", task.getId())
+                 .addData("type", task.getType())
+                 .addData("dataSource", task.getDataSource())
+                 .addData("interval", task.getFixedInterval())
+                 .emit();
             }
 
-            if (!task.getInterval().contains(segment.getInterval())) {
-              throw new IllegalStateException(
-                  String.format(
-                      "Segment for task[%s] has invalid interval: %s",
-                      task.getId(),
-                      segment.getIdentifier()
-                  )
-              );
-            }
-
-            if (!context.getVersion().equals(segment.getVersion())) {
-              throw new IllegalStateException(
-                  String.format(
-                      "Segment for task[%s] has invalid version: %s",
-                      task.getId(),
-                      segment.getIdentifier()
-                  )
-              );
-            }
-
-            log.info("Publishing segment[%s] for task[%s]", segment.getIdentifier(), task.getId());
-            mergerDBCoordinator.announceHistoricalSegment(segment);
+            log.info(
+                "Task %s: %s (%d run duration)",
+                statusFromRunner.getStatusCode(),
+                task,
+                statusFromRunner.getDuration()
+            );
           }
         }
         catch (Exception e) {
-          log.error(e, "Exception while publishing segments for task: %s", task);
-          status = TaskStatus.failure(task.getId()).withDuration(status.getDuration());
-        }
-
-        try {
-          queue.done(task, status);
-        }
-        catch (Exception e) {
-          log.error(e, "Exception while marking task done: %s", task);
-          throw Throwables.propagate(e);
-        }
-
-        // emit event and log
-        int bytes = 0;
-        for (DataSegment segment : status.getSegments()) {
-          bytes += segment.getSize();
-        }
-
-        builder.setUser3(status.getStatusCode().toString());
-
-        emitter.emit(builder.build("indexer/time/run/millis", status.getDuration()));
-        emitter.emit(builder.build("indexer/segment/count", status.getSegments().size()));
-        emitter.emit(builder.build("indexer/segment/bytes", bytes));
-
-        if (status.isFailure()) {
-          log.makeAlert("Failed to index")
+          log.makeAlert(e, "Failed to handle task callback")
              .addData("task", task.getId())
-             .addData("type", task.getType().toString())
-             .addData("dataSource", task.getDataSource())
-             .addData("interval", task.getInterval())
+             .addData("statusCode", statusFromRunner.getStatusCode())
              .emit();
         }
-
-        log.info(
-            "Task %s: %s (%d segments) (%d run duration)",
-            status.getStatusCode(),
-            task,
-            status.getSegments().size(),
-            status.getDuration()
-        );
-
       }
     }
     );

merger/src/main/java/com/metamx/druid/merger/coordinator/http/IndexerCoordinatorInfoResource.java

@@ -0,0 +1,67 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator.http;
+
+import com.google.inject.Inject;
+import com.metamx.common.logger.Logger;
+import com.metamx.druid.merger.coordinator.TaskMasterLifecycle;
+
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.Produces;
+import javax.ws.rs.core.Response;
+
+/**
+ */
+@Path("/mmx/merger/v1/info")
+public class IndexerCoordinatorInfoResource
+{
+  private static final Logger log = new Logger(IndexerCoordinatorInfoResource.class);
+
+  private final TaskMasterLifecycle taskMasterLifecycle;
+
+  @Inject
+  public IndexerCoordinatorInfoResource(TaskMasterLifecycle taskMasterLifecycle)
+  {
+    this.taskMasterLifecycle = taskMasterLifecycle;
+  }
+
+  @GET
+  @Path("/pendingTasks}")
+  @Produces("application/json")
+  public Response getPendingTasks()
+  {
+    if (taskMasterLifecycle.getTaskRunner() == null) {
+      return Response.noContent().build();
+    }
+    return Response.ok(taskMasterLifecycle.getTaskRunner().getPendingTasks()).build();
+  }
+
+  @GET
+  @Path("/runningTasks}")
+  @Produces("application/json")
+  public Response getRunningTasks()
+  {
+    if (taskMasterLifecycle.getTaskRunner() == null) {
+      return Response.noContent().build();
+    }
+    return Response.ok(taskMasterLifecycle.getTaskRunner().getRunningTasks()).build();
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/http/IndexerCoordinatorNode.java

@@ -49,11 +49,16 @@ import com.metamx.druid.initialization.Initialization;
 import com.metamx.druid.initialization.ServerConfig;
 import com.metamx.druid.initialization.ServiceDiscoveryConfig;
 import com.metamx.druid.jackson.DefaultObjectMapper;
-import com.metamx.druid.loading.S3SegmentPusher;
-import com.metamx.druid.loading.S3SegmentPusherConfig;
-import com.metamx.druid.loading.SegmentPusher;
+import com.metamx.druid.loading.DataSegmentPusher;
+import com.metamx.druid.loading.S3DataSegmentPusher;
+import com.metamx.druid.loading.S3DataSegmentPusherConfig;
+import com.metamx.druid.loading.S3SegmentKiller;
+import com.metamx.druid.loading.SegmentKiller;
 import com.metamx.druid.merger.common.TaskToolbox;
+import com.metamx.druid.merger.common.actions.LocalTaskActionClient;
+import com.metamx.druid.merger.common.actions.TaskActionToolbox;
 import com.metamx.druid.merger.common.config.IndexerZkConfig;
+import com.metamx.druid.merger.common.config.TaskConfig;
 import com.metamx.druid.merger.common.index.StaticS3FirehoseFactory;
 import com.metamx.druid.merger.coordinator.DbTaskStorage;
 import com.metamx.druid.merger.coordinator.LocalTaskRunner;
@@ -61,20 +66,27 @@ import com.metamx.druid.merger.coordinator.LocalTaskStorage;
 import com.metamx.druid.merger.coordinator.MergerDBCoordinator;
 import com.metamx.druid.merger.coordinator.RemoteTaskRunner;
 import com.metamx.druid.merger.coordinator.RetryPolicyFactory;
-import com.metamx.druid.merger.coordinator.TaskMaster;
+import com.metamx.druid.merger.coordinator.TaskLockbox;
+import com.metamx.druid.merger.coordinator.TaskMasterLifecycle;
 import com.metamx.druid.merger.coordinator.TaskQueue;
 import com.metamx.druid.merger.coordinator.TaskRunner;
 import com.metamx.druid.merger.coordinator.TaskRunnerFactory;
 import com.metamx.druid.merger.coordinator.TaskStorage;
+import com.metamx.druid.merger.coordinator.TaskStorageQueryAdapter;
 import com.metamx.druid.merger.coordinator.config.EC2AutoScalingStrategyConfig;
 import com.metamx.druid.merger.coordinator.config.IndexerCoordinatorConfig;
 import com.metamx.druid.merger.coordinator.config.IndexerDbConnectorConfig;
 import com.metamx.druid.merger.coordinator.config.RemoteTaskRunnerConfig;
 import com.metamx.druid.merger.coordinator.config.RetryPolicyConfig;
 import com.metamx.druid.merger.coordinator.config.WorkerSetupManagerConfig;
+import com.metamx.druid.merger.coordinator.scaling.AutoScalingStrategy;
 import com.metamx.druid.merger.coordinator.scaling.EC2AutoScalingStrategy;
-import com.metamx.druid.merger.coordinator.scaling.NoopScalingStrategy;
-import com.metamx.druid.merger.coordinator.scaling.ScalingStrategy;
+import com.metamx.druid.merger.coordinator.scaling.NoopAutoScalingStrategy;
+import com.metamx.druid.merger.coordinator.scaling.ResourceManagementScheduler;
+import com.metamx.druid.merger.coordinator.scaling.ResourceManagementSchedulerConfig;
+import com.metamx.druid.merger.coordinator.scaling.ResourceManagementSchedulerFactory;
+import com.metamx.druid.merger.coordinator.scaling.SimpleResourceManagementStrategy;
+import com.metamx.druid.merger.coordinator.scaling.SimpleResourceManagmentConfig;
 import com.metamx.druid.merger.coordinator.setup.WorkerSetupManager;
 import com.metamx.druid.utils.PropUtils;
 import com.metamx.emitter.EmittingLogger;
@@ -91,8 +103,6 @@ import com.metamx.metrics.MonitorSchedulerConfig;
 import com.metamx.metrics.SysMonitor;
 import com.netflix.curator.framework.CuratorFramework;
 import com.netflix.curator.framework.recipes.cache.PathChildrenCache;
-
-
 import org.jets3t.service.S3ServiceException;
 import org.jets3t.service.impl.rest.httpclient.RestS3Service;
 import org.jets3t.service.security.AWSCredentials;
@@ -130,17 +140,23 @@ public class IndexerCoordinatorNode extends RegisteringNode
 
   private List<Monitor> monitors = null;
   private ServiceEmitter emitter = null;
+  private DbConnectorConfig dbConnectorConfig = null;
+  private DBI dbi = null;
+  private RestS3Service s3Service = null;
   private IndexerCoordinatorConfig config = null;
+  private TaskConfig taskConfig = null;
   private TaskToolbox taskToolbox = null;
   private MergerDBCoordinator mergerDBCoordinator = null;
   private TaskStorage taskStorage = null;
   private TaskQueue taskQueue = null;
+  private TaskLockbox taskLockbox = null;
   private CuratorFramework curatorFramework = null;
   private ScheduledExecutorFactory scheduledExecutorFactory = null;
   private IndexerZkConfig indexerZkConfig;
   private WorkerSetupManager workerSetupManager = null;
   private TaskRunnerFactory taskRunnerFactory = null;
-  private TaskMaster taskMaster = null;
+  private ResourceManagementSchedulerFactory resourceManagementSchedulerFactory = null;
+  private TaskMasterLifecycle taskMasterLifecycle = null;
   private Server server = null;
 
   private boolean initialized = false;
@@ -178,6 +194,18 @@ public class IndexerCoordinatorNode extends RegisteringNode
     return this;
   }
 
+  public IndexerCoordinatorNode setS3Service(RestS3Service s3Service)
+  {
+    this.s3Service = s3Service;
+    return this;
+  }
+
+  public IndexerCoordinatorNode setTaskLockbox(TaskLockbox taskLockbox)
+  {
+    this.taskLockbox = taskLockbox;
+    return this;
+  }
+
   public IndexerCoordinatorNode setMergeDbCoordinator(MergerDBCoordinator mergeDbCoordinator)
   {
     this.mergerDBCoordinator = mergeDbCoordinator;
@@ -202,24 +230,35 @@ public class IndexerCoordinatorNode extends RegisteringNode
     return this;
   }
 
+  public IndexerCoordinatorNode setResourceManagementSchedulerFactory(ResourceManagementSchedulerFactory resourceManagementSchedulerFactory)
+  {
+    this.resourceManagementSchedulerFactory = resourceManagementSchedulerFactory;
+    return this;
+  }
+
   public void init() throws Exception
   {
     scheduledExecutorFactory = ScheduledExecutors.createFactory(lifecycle);
 
     initializeEmitter();
     initializeMonitors();
+    initializeDB();
     initializeIndexerCoordinatorConfig();
+    initializeTaskConfig();
+    initializeS3Service();
     initializeMergeDBCoordinator();
-    initializeTaskToolbox();
     initializeTaskStorage();
+    initializeTaskLockbox();
     initializeTaskQueue();
+    initializeTaskToolbox();
     initializeJacksonInjections();
     initializeJacksonSubtypes();
     initializeCurator();
     initializeIndexerZkConfig();
     initializeWorkerSetupManager();
     initializeTaskRunnerFactory();
-    initializeTaskMaster();
+    initializeResourceManagement();
+    initializeTaskMasterLifecycle();
     initializeServer();
 
     final ScheduledExecutorService globalScheduledExec = scheduledExecutorFactory.create(1, "Global--%d");
@@ -236,7 +275,8 @@ public class IndexerCoordinatorNode extends RegisteringNode
             jsonMapper,
             config,
             emitter,
-            taskQueue,
+            taskMasterLifecycle,
+            new TaskStorageQueryAdapter(taskStorage),
             workerSetupManager
         )
     );
@@ -255,7 +295,7 @@ public class IndexerCoordinatorNode extends RegisteringNode
                   @Override
                   public boolean doLocal()
                   {
-                    return taskMaster.isLeading();
+                    return taskMasterLifecycle.isLeading();
                   }
 
                   @Override
@@ -265,7 +305,7 @@ public class IndexerCoordinatorNode extends RegisteringNode
                       return new URL(
                           String.format(
                               "http://%s%s",
-                              taskMaster.getLeader(),
+                              taskMasterLifecycle.getLeader(),
                               requestURI
                           )
                       );
@@ -283,20 +323,21 @@ public class IndexerCoordinatorNode extends RegisteringNode
     initialized = true;
   }
 
-  private void initializeTaskMaster()
+  private void initializeTaskMasterLifecycle()
   {
-    if (taskMaster == null) {
+    if (taskMasterLifecycle == null) {
       final ServiceDiscoveryConfig serviceDiscoveryConfig = configFactory.build(ServiceDiscoveryConfig.class);
-      taskMaster = new TaskMaster(
+      taskMasterLifecycle = new TaskMasterLifecycle(
           taskQueue,
+          taskToolbox,
           config,
           serviceDiscoveryConfig,
-          mergerDBCoordinator,
           taskRunnerFactory,
+          resourceManagementSchedulerFactory,
           curatorFramework,
           emitter
       );
-      lifecycle.addManagedInstance(taskMaster);
+      lifecycle.addManagedInstance(taskMasterLifecycle);
     }
   }
 
@@ -351,7 +392,7 @@ public class IndexerCoordinatorNode extends RegisteringNode
   {
     InjectableValues.Std injectables = new InjectableValues.Std();
 
-    injectables.addValue("s3Client", taskToolbox.getS3Client())
+    injectables.addValue("s3Client", s3Service)
                .addValue("segmentPusher", taskToolbox.getSegmentPusher());
 
     jsonMapper.setInjectableValues(injectables);
@@ -387,6 +428,16 @@ public class IndexerCoordinatorNode extends RegisteringNode
     }
   }
 
+  private void initializeDB()
+  {
+    if (dbConnectorConfig == null) {
+      dbConnectorConfig = configFactory.build(DbConnectorConfig.class);
+    }
+    if (dbi == null) {
+      dbi = new DbConnector(dbConnectorConfig).getDBI();
+    }
+  }
+
   private void initializeIndexerCoordinatorConfig()
   {
     if (config == null) {
@@ -394,32 +445,56 @@ public class IndexerCoordinatorNode extends RegisteringNode
     }
   }
 
-  public void initializeTaskToolbox() throws S3ServiceException
+  private void initializeTaskConfig()
+  {
+    if (taskConfig == null) {
+      taskConfig = configFactory.build(TaskConfig.class);
+    }
+  }
+
+  public void initializeS3Service() throws S3ServiceException
+  {
+    this.s3Service = new RestS3Service(
+        new AWSCredentials(
+            PropUtils.getProperty(props, "com.metamx.aws.accessKey"),
+            PropUtils.getProperty(props, "com.metamx.aws.secretKey")
+        )
+    );
+  }
+
+  public void initializeTaskToolbox()
   {
     if (taskToolbox == null) {
-      final RestS3Service s3Client = new RestS3Service(
-          new AWSCredentials(
-              PropUtils.getProperty(props, "com.metamx.aws.accessKey"),
-              PropUtils.getProperty(props, "com.metamx.aws.secretKey")
-          )
-      );
-      final SegmentPusher segmentPusher = new S3SegmentPusher(
-          s3Client,
-          configFactory.build(S3SegmentPusherConfig.class),
+      final DataSegmentPusher dataSegmentPusher = new S3DataSegmentPusher(
+          s3Service,
+          configFactory.build(S3DataSegmentPusherConfig.class),
+          jsonMapper
+      );
+      final SegmentKiller segmentKiller = new S3SegmentKiller(
+          s3Service
+      );
+      taskToolbox = new TaskToolbox(
+          taskConfig,
+          new LocalTaskActionClient(
+              taskStorage,
+              new TaskActionToolbox(taskQueue, taskLockbox, mergerDBCoordinator, emitter)
+          ),
+          emitter,
+          s3Service,
+          dataSegmentPusher,
+          segmentKiller,
           jsonMapper
       );
-      taskToolbox = new TaskToolbox(config, emitter, s3Client, segmentPusher, jsonMapper);
     }
   }
 
   public void initializeMergeDBCoordinator()
   {
     if (mergerDBCoordinator == null) {
-      final DbConnectorConfig dbConnectorConfig = configFactory.build(DbConnectorConfig.class);
       mergerDBCoordinator = new MergerDBCoordinator(
           jsonMapper,
           dbConnectorConfig,
-          new DbConnector(dbConnectorConfig).getDBI()
+          dbi
       );
     }
   }
@@ -427,8 +502,15 @@ public class IndexerCoordinatorNode extends RegisteringNode
   public void initializeTaskQueue()
   {
     if (taskQueue == null) {
-      // Don't start it here. The TaskMaster will handle that when it feels like it.
-      taskQueue = new TaskQueue(taskStorage);
+      // Don't start it here. The TaskMasterLifecycle will handle that when it feels like it.
+      taskQueue = new TaskQueue(taskStorage, taskLockbox);
+    }
+  }
+
+  public void initializeTaskLockbox()
+  {
+    if (taskLockbox == null) {
+      taskLockbox = new TaskLockbox(taskStorage);
     }
   }
 
@@ -467,8 +549,6 @@ public class IndexerCoordinatorNode extends RegisteringNode
   public void initializeWorkerSetupManager()
   {
     if (workerSetupManager == null) {
-      final DbConnectorConfig dbConnectorConfig = configFactory.build(DbConnectorConfig.class);
-      final DBI dbi = new DbConnector(dbConnectorConfig).getDBI();
       final WorkerSetupManagerConfig workerSetupManagerConfig = configFactory.build(WorkerSetupManagerConfig.class);
 
       DbConnector.createConfigTable(dbi, workerSetupManagerConfig.getConfigTable());
@@ -504,35 +584,17 @@ public class IndexerCoordinatorNode extends RegisteringNode
                     .build()
             );
 
-            ScalingStrategy strategy;
-            if (config.getStrategyImpl().equalsIgnoreCase("ec2")) {
-              strategy = new EC2AutoScalingStrategy(
-                  jsonMapper,
-                  new AmazonEC2Client(
-                      new BasicAWSCredentials(
-                          PropUtils.getProperty(props, "com.metamx.aws.accessKey"),
-                          PropUtils.getProperty(props, "com.metamx.aws.secretKey")
-                      )
-                  ),
-                  configFactory.build(EC2AutoScalingStrategyConfig.class),
-                  workerSetupManager
-              );
-            } else if (config.getStrategyImpl().equalsIgnoreCase("noop")) {
-              strategy = new NoopScalingStrategy();
-            } else {
-              throw new ISE("Invalid strategy implementation: %s", config.getStrategyImpl());
-            }
-
-            return new RemoteTaskRunner(
+            RemoteTaskRunner remoteTaskRunner = new RemoteTaskRunner(
                 jsonMapper,
                 configFactory.build(RemoteTaskRunnerConfig.class),
                 curatorFramework,
                 new PathChildrenCache(curatorFramework, indexerZkConfig.getAnnouncementPath(), true),
                 retryScheduledExec,
                 new RetryPolicyFactory(configFactory.build(RetryPolicyConfig.class)),
-                strategy,
                 workerSetupManager
             );
+
+            return remoteTaskRunner;
           }
         };
 
@@ -552,6 +614,56 @@ public class IndexerCoordinatorNode extends RegisteringNode
     }
   }
 
+  private void initializeResourceManagement()
+  {
+    if (resourceManagementSchedulerFactory == null) {
+      resourceManagementSchedulerFactory = new ResourceManagementSchedulerFactory()
+      {
+        @Override
+        public ResourceManagementScheduler build(TaskRunner runner)
+        {
+          final ScheduledExecutorService scalingScheduledExec = Executors.newScheduledThreadPool(
+              1,
+              new ThreadFactoryBuilder()
+                  .setDaemon(true)
+                  .setNameFormat("ScalingExec--%d")
+                  .build()
+          );
+
+          AutoScalingStrategy strategy;
+          if (config.getStrategyImpl().equalsIgnoreCase("ec2")) {
+            strategy = new EC2AutoScalingStrategy(
+                jsonMapper,
+                new AmazonEC2Client(
+                    new BasicAWSCredentials(
+                        PropUtils.getProperty(props, "com.metamx.aws.accessKey"),
+                        PropUtils.getProperty(props, "com.metamx.aws.secretKey")
+                    )
+                ),
+                configFactory.build(EC2AutoScalingStrategyConfig.class),
+                workerSetupManager
+            );
+          } else if (config.getStrategyImpl().equalsIgnoreCase("noop")) {
+            strategy = new NoopAutoScalingStrategy();
+          } else {
+            throw new ISE("Invalid strategy implementation: %s", config.getStrategyImpl());
+          }
+
+          return new ResourceManagementScheduler(
+              runner,
+              new SimpleResourceManagementStrategy(
+                  strategy,
+                  configFactory.build(SimpleResourceManagmentConfig.class),
+                  workerSetupManager
+              ),
+              configFactory.build(ResourceManagementSchedulerConfig.class),
+              scalingScheduledExec
+          );
+        }
+      };
+    }
+  }
+
   public static class Builder
   {
     private ObjectMapper jsonMapper = null;

merger/src/main/java/com/metamx/druid/merger/coordinator/http/IndexerCoordinatorResource.java

@@ -21,16 +21,21 @@ package com.metamx.druid.merger.coordinator.http;
 
 import com.google.common.base.Optional;
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Maps;
 import com.google.inject.Inject;
 import com.metamx.common.logger.Logger;
+import com.metamx.druid.client.DataSegment;
 import com.metamx.druid.merger.common.TaskStatus;
-import com.metamx.druid.merger.common.task.MergeTask;
+import com.metamx.druid.merger.common.actions.TaskAction;
 import com.metamx.druid.merger.common.task.Task;
-import com.metamx.druid.merger.coordinator.TaskQueue;
+import com.metamx.druid.merger.coordinator.TaskMasterLifecycle;
+import com.metamx.druid.merger.coordinator.TaskStorageQueryAdapter;
 import com.metamx.druid.merger.coordinator.config.IndexerCoordinatorConfig;
 import com.metamx.druid.merger.coordinator.setup.WorkerSetupData;
 import com.metamx.druid.merger.coordinator.setup.WorkerSetupManager;
 import com.metamx.emitter.service.ServiceEmitter;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.core.type.TypeReference;
 
 import javax.ws.rs.Consumes;
 import javax.ws.rs.GET;
@@ -39,6 +44,8 @@ import javax.ws.rs.Path;
 import javax.ws.rs.PathParam;
 import javax.ws.rs.Produces;
 import javax.ws.rs.core.Response;
+import java.util.Map;
+import java.util.Set;
 
 /**
  */
@@ -49,31 +56,34 @@ public class IndexerCoordinatorResource
 
   private final IndexerCoordinatorConfig config;
   private final ServiceEmitter emitter;
-  private final TaskQueue tasks;
+  private final TaskMasterLifecycle taskMasterLifecycle;
+  private final TaskStorageQueryAdapter taskStorageQueryAdapter;
   private final WorkerSetupManager workerSetupManager;
+  private final ObjectMapper jsonMapper;
 
   @Inject
   public IndexerCoordinatorResource(
       IndexerCoordinatorConfig config,
       ServiceEmitter emitter,
-      TaskQueue tasks,
-      WorkerSetupManager workerSetupManager
-
+      TaskMasterLifecycle taskMasterLifecycle,
+      TaskStorageQueryAdapter taskStorageQueryAdapter,
+      WorkerSetupManager workerSetupManager,
+      ObjectMapper jsonMapper
   ) throws Exception
   {
     this.config = config;
     this.emitter = emitter;
-    this.tasks = tasks;
+    this.taskMasterLifecycle = taskMasterLifecycle;
+    this.taskStorageQueryAdapter = taskStorageQueryAdapter;
     this.workerSetupManager = workerSetupManager;
+    this.jsonMapper = jsonMapper;
   }
 
   @POST
   @Path("/merge")
   @Consumes("application/json")
   @Produces("application/json")
-  public Response doMerge(
-      final MergeTask task
-  )
+  public Response doMerge(final Task task)
   {
     // legacy endpoint
     return doIndex(task);
@@ -83,9 +93,7 @@ public class IndexerCoordinatorResource
   @Path("/index")
   @Consumes("application/json")
   @Produces("application/json")
-  public Response doIndex(
-      final Task task
-  )
+  public Response doIndex(final Task task)
   {
     // verify against whitelist
     if (config.isWhitelistEnabled() && !config.getWhitelistDatasources().contains(task.getDataSource())) {
@@ -99,16 +107,16 @@ public class IndexerCoordinatorResource
                      .build();
     }
 
-    tasks.add(task);
-    return okResponse(task.getId());
+    taskMasterLifecycle.getTaskQueue().add(task);
+    return Response.ok(ImmutableMap.of("task", task.getId())).build();
   }
 
   @GET
-  @Path("/status/{taskid}")
+  @Path("/task/{taskid}/status")
   @Produces("application/json")
-  public Response doStatus(@PathParam("taskid") String taskid)
+  public Response getTaskStatus(@PathParam("taskid") String taskid)
   {
-    final Optional<TaskStatus> status = tasks.getStatus(taskid);
+    final Optional<TaskStatus> status = taskStorageQueryAdapter.getSameGroupMergedStatus(taskid);
     if (!status.isPresent()) {
       return Response.status(Response.Status.NOT_FOUND).build();
     } else {
@@ -116,9 +124,30 @@ public class IndexerCoordinatorResource
     }
   }
 
-  private Response okResponse(final String taskid)
+  @GET
+  @Path("/task/{taskid}/segments")
+  @Produces("application/json")
+  public Response getTaskSegments(@PathParam("taskid") String taskid)
   {
-    return Response.ok(ImmutableMap.of("task", taskid)).build();
+    final Set<DataSegment> segments = taskStorageQueryAdapter.getSameGroupNewSegments(taskid);
+    return Response.ok().entity(segments).build();
+  }
+
+  // Legacy endpoint
+  // TODO Remove
+  @Deprecated
+  @GET
+  @Path("/status/{taskid}")
+  @Produces("application/json")
+  public Response getLegacyStatus(@PathParam("taskid") String taskid)
+  {
+    final Optional<TaskStatus> status = taskStorageQueryAdapter.getSameGroupMergedStatus(taskid);
+    final Set<DataSegment> segments = taskStorageQueryAdapter.getSameGroupNewSegments(taskid);
+
+    final Map<String, Object> ret = jsonMapper.convertValue(status, new TypeReference<Map<String, Object>>(){});
+    ret.put("segments", segments);
+
+    return Response.ok().entity(ret).build();
   }
 
   @GET
@@ -141,4 +170,16 @@ public class IndexerCoordinatorResource
     }
     return Response.ok().build();
   }
+
+  @POST
+  @Path("/action")
+  @Produces("application/json")
+  public <T> Response doAction(final TaskAction<T> action)
+  {
+    final T ret = taskMasterLifecycle.getTaskToolbox().getTaskActionClient().submit(action);
+    final Map<String, Object> retMap = Maps.newHashMap();
+    retMap.put("result", ret);
+
+    return Response.ok().entity(retMap).build();
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/http/IndexerCoordinatorServletModule.java

@@ -22,15 +22,14 @@ package com.metamx.druid.merger.coordinator.http;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider;
 import com.google.inject.Provides;
-import com.metamx.druid.merger.coordinator.TaskQueue;
+import com.metamx.druid.merger.coordinator.TaskMasterLifecycle;
+import com.metamx.druid.merger.coordinator.TaskStorageQueryAdapter;
 import com.metamx.druid.merger.coordinator.config.IndexerCoordinatorConfig;
 import com.metamx.druid.merger.coordinator.setup.WorkerSetupManager;
 import com.metamx.emitter.service.ServiceEmitter;
 import com.sun.jersey.guice.JerseyServletModule;
 import com.sun.jersey.guice.spi.container.servlet.GuiceContainer;
 
-
-
 import javax.inject.Singleton;
 
 /**
@@ -40,21 +39,24 @@ public class IndexerCoordinatorServletModule extends JerseyServletModule
   private final ObjectMapper jsonMapper;
   private final IndexerCoordinatorConfig indexerCoordinatorConfig;
   private final ServiceEmitter emitter;
-  private final TaskQueue tasks;
+  private final TaskMasterLifecycle taskMasterLifecycle;
+  private final TaskStorageQueryAdapter taskStorageQueryAdapter;
   private final WorkerSetupManager workerSetupManager;
 
   public IndexerCoordinatorServletModule(
       ObjectMapper jsonMapper,
       IndexerCoordinatorConfig indexerCoordinatorConfig,
       ServiceEmitter emitter,
-      TaskQueue tasks,
+      TaskMasterLifecycle taskMasterLifecycle,
+      TaskStorageQueryAdapter taskStorageQueryAdapter,
       WorkerSetupManager workerSetupManager
   )
   {
     this.jsonMapper = jsonMapper;
     this.indexerCoordinatorConfig = indexerCoordinatorConfig;
     this.emitter = emitter;
-    this.tasks = tasks;
+    this.taskMasterLifecycle = taskMasterLifecycle;
+    this.taskStorageQueryAdapter = taskStorageQueryAdapter;
     this.workerSetupManager = workerSetupManager;
   }
 
@@ -62,10 +64,12 @@ public class IndexerCoordinatorServletModule extends JerseyServletModule
   protected void configureServlets()
   {
     bind(IndexerCoordinatorResource.class);
+    bind(IndexerCoordinatorInfoResource.class);
     bind(ObjectMapper.class).toInstance(jsonMapper);
     bind(IndexerCoordinatorConfig.class).toInstance(indexerCoordinatorConfig);
     bind(ServiceEmitter.class).toInstance(emitter);
-    bind(TaskQueue.class).toInstance(tasks);
+    bind(TaskMasterLifecycle.class).toInstance(taskMasterLifecycle);
+    bind(TaskStorageQueryAdapter.class).toInstance(taskStorageQueryAdapter);
     bind(WorkerSetupManager.class).toInstance(workerSetupManager);
 
     serve("/*").with(GuiceContainer.class);

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/AutoScalingData.java

@@ -43,4 +43,13 @@ public class AutoScalingData<T>
   {
     return nodes;
   }
+
+  @Override
+  public String toString()
+  {
+    return "AutoScalingData{" +
+           "nodeIds=" + nodeIds +
+           ", nodes=" + nodes +
+           '}';
+  }
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/AutoScalingStrategy.java

@@ -22,8 +22,9 @@ package com.metamx.druid.merger.coordinator.scaling;
 import java.util.List;
 
 /**
+ * The AutoScalingStrategy has the actual methods to provision and terminate worker nodes.
  */
-public interface ScalingStrategy<T>
+public interface AutoScalingStrategy<T>
 {
   public AutoScalingData<T> provision();
 
@@ -31,8 +32,8 @@ public interface ScalingStrategy<T>
 
   /**
    * Provides a lookup of ip addresses to node ids
-   * @param ips
-   * @return
+   * @param ips - nodes ips
+   * @return node ids
    */
-  public List<String> ipLookup(List<String> ips);
+  public List<String> ipToIdLookup(List<String> ips);
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/EC2AutoScalingStrategy.java

@@ -44,7 +44,7 @@ import java.util.List;
 
 /**
  */
-public class EC2AutoScalingStrategy implements ScalingStrategy<Instance>
+public class EC2AutoScalingStrategy implements AutoScalingStrategy<Instance>
 {
   private static final EmittingLogger log = new EmittingLogger(EC2AutoScalingStrategy.class);
 
@@ -73,7 +73,6 @@ public class EC2AutoScalingStrategy implements ScalingStrategy<Instance>
       WorkerSetupData setupData = workerSetupManager.getWorkerSetupData();
       EC2NodeData workerConfig = setupData.getNodeData();
 
-      log.info("Creating new instance(s)...");
       RunInstancesResult result = amazonEC2Client.runInstances(
           new RunInstancesRequest(
               workerConfig.getAmiId(),
@@ -131,6 +130,10 @@ public class EC2AutoScalingStrategy implements ScalingStrategy<Instance>
   @Override
   public AutoScalingData<Instance> terminate(List<String> ids)
   {
+    if (ids.isEmpty()) {
+      return new AutoScalingData<Instance>(Lists.<String>newArrayList(), Lists.<Instance>newArrayList());
+    }
+
     DescribeInstancesResult result = amazonEC2Client.describeInstances(
         new DescribeInstancesRequest()
             .withFilters(
@@ -184,7 +187,7 @@ public class EC2AutoScalingStrategy implements ScalingStrategy<Instance>
   }
 
   @Override
-  public List<String> ipLookup(List<String> ips)
+  public List<String> ipToIdLookup(List<String> ips)
   {
     DescribeInstancesResult result = amazonEC2Client.describeInstances(
         new DescribeInstancesRequest()

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/NoopAutoScalingStrategy.java

@@ -26,9 +26,9 @@ import java.util.List;
 /**
  * This class just logs when scaling should occur.
  */
-public class NoopScalingStrategy implements ScalingStrategy<String>
+public class NoopAutoScalingStrategy implements AutoScalingStrategy<String>
 {
-  private static final EmittingLogger log = new EmittingLogger(NoopScalingStrategy.class);
+  private static final EmittingLogger log = new EmittingLogger(NoopAutoScalingStrategy.class);
 
   @Override
   public AutoScalingData<String> provision()
@@ -45,7 +45,7 @@ public class NoopScalingStrategy implements ScalingStrategy<String>
   }
 
   @Override
-  public List<String> ipLookup(List<String> ips)
+  public List<String> ipToIdLookup(List<String> ips)
   {
     log.info("I'm not a real strategy so I'm returning what I got %s", ips);
     return ips;

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/ResourceManagementScheduler.java

@@ -0,0 +1,135 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator.scaling;
+
+import com.metamx.common.concurrent.ScheduledExecutors;
+import com.metamx.common.lifecycle.LifecycleStart;
+import com.metamx.common.lifecycle.LifecycleStop;
+import com.metamx.common.logger.Logger;
+import com.metamx.druid.PeriodGranularity;
+import com.metamx.druid.merger.coordinator.TaskRunner;
+import org.joda.time.DateTime;
+import org.joda.time.Duration;
+import org.joda.time.Period;
+
+import java.util.concurrent.ScheduledExecutorService;
+
+/**
+ * The ResourceManagementScheduler schedules a check for when worker nodes should potentially be created or destroyed.
+ * It uses a {@link TaskRunner} to return all pending tasks in the system and the status of the worker nodes in
+ * the system.
+ * The ResourceManagementScheduler does not contain the logic to decide whether provision or termination should actually
+ * occur. That decision is made in the {@link ResourceManagementStrategy}.
+ */
+public class ResourceManagementScheduler
+{
+  private static final Logger log = new Logger(ResourceManagementScheduler.class);
+
+  private final TaskRunner taskRunner;
+  private final ResourceManagementStrategy resourceManagementStrategy;
+  private final ResourceManagementSchedulerConfig config;
+  private final ScheduledExecutorService exec;
+
+  private final Object lock = new Object();
+  private volatile boolean started = false;
+
+  public ResourceManagementScheduler(
+      TaskRunner taskRunner,
+      ResourceManagementStrategy resourceManagementStrategy,
+      ResourceManagementSchedulerConfig config,
+      ScheduledExecutorService exec
+  )
+  {
+    this.taskRunner = taskRunner;
+    this.resourceManagementStrategy = resourceManagementStrategy;
+    this.config = config;
+    this.exec = exec;
+  }
+
+  @LifecycleStart
+  public void start()
+  {
+    synchronized (lock) {
+      if (started) {
+        return;
+      }
+
+      ScheduledExecutors.scheduleAtFixedRate(
+          exec,
+          config.getProvisionResourcesDuration(),
+          new Runnable()
+          {
+            @Override
+            public void run()
+            {
+              resourceManagementStrategy.doProvision(
+                  taskRunner.getPendingTasks(),
+                  taskRunner.getWorkers()
+              );
+            }
+          }
+      );
+
+      // Schedule termination of worker nodes periodically
+      Period period = new Period(config.getTerminateResourcesDuration());
+      PeriodGranularity granularity = new PeriodGranularity(period, config.getTerminateResourcesOriginDateTime(), null);
+      final long startTime = granularity.next(granularity.truncate(new DateTime().getMillis()));
+
+      ScheduledExecutors.scheduleAtFixedRate(
+          exec,
+          new Duration(
+              System.currentTimeMillis(),
+              startTime
+          ),
+          config.getTerminateResourcesDuration(),
+          new Runnable()
+          {
+            @Override
+            public void run()
+            {
+              resourceManagementStrategy.doTerminate(
+                  taskRunner.getPendingTasks(),
+                  taskRunner.getWorkers()
+              );
+            }
+          }
+      );
+
+      started = true;
+    }
+  }
+
+  @LifecycleStop
+  public void stop()
+  {
+    synchronized (lock) {
+      if (!started) {
+        return;
+      }
+      exec.shutdown();
+      started = false;
+    }
+  }
+
+  public ScalingStats getStats()
+  {
+    return resourceManagementStrategy.getStats();
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/ResourceManagementSchedulerConfig.java

@@ -0,0 +1,42 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator.scaling;
+
+import org.joda.time.DateTime;
+import org.joda.time.Duration;
+import org.skife.config.Config;
+import org.skife.config.Default;
+
+/**
+ */
+public abstract class ResourceManagementSchedulerConfig
+{
+  @Config("druid.indexer.provisionResources.duration")
+  @Default("PT1M")
+  public abstract Duration getProvisionResourcesDuration();
+
+  @Config("druid.indexer.terminateResources.duration")
+  @Default("PT1H")
+  public abstract Duration getTerminateResourcesDuration();
+
+  @Config("druid.indexer.terminateResources.originDateTime")
+  @Default("2012-01-01T00:55:00.000Z")
+  public abstract DateTime getTerminateResourcesOriginDateTime();
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/ResourceManagementSchedulerFactory.java

@@ -17,17 +17,13 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
-package com.metamx.druid.loading;
+package com.metamx.druid.merger.coordinator.scaling;
 
-import org.skife.config.Config;
+import com.metamx.druid.merger.coordinator.TaskRunner;
 
 /**
  */
-public abstract class QueryableLoaderConfig extends S3SegmentGetterConfig
+public interface ResourceManagementSchedulerFactory
 {
-  @Config("druid.queryable.factory")
-  public String getQueryableFactoryType()
-  {
-    return "mmap";
-  }
+  public ResourceManagementScheduler build(TaskRunner runner);
 }

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/ResourceManagementStrategy.java

@@ -0,0 +1,38 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator.scaling;
+
+import com.metamx.druid.merger.coordinator.TaskRunnerWorkItem;
+import com.metamx.druid.merger.coordinator.ZkWorker;
+
+import java.util.Collection;
+
+/**
+ * The ResourceManagementStrategy decides if worker nodes should be provisioned or determined
+ * based on the available tasks in the system and the state of the workers in the system.
+ */
+public interface ResourceManagementStrategy
+{
+  public boolean doProvision(Collection<TaskRunnerWorkItem> runningTasks, Collection<ZkWorker> zkWorkers);
+
+  public boolean doTerminate(Collection<TaskRunnerWorkItem> runningTasks, Collection<ZkWorker> zkWorkers);
+
+  public ScalingStats getStats();
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/ScalingStats.java

@@ -0,0 +1,112 @@
+package com.metamx.druid.merger.coordinator.scaling;
+
+import com.google.common.collect.Lists;
+import com.google.common.collect.MinMaxPriorityQueue;
+import org.joda.time.DateTime;
+
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+/**
+ */
+public class ScalingStats
+{
+  public static enum EVENT
+  {
+    PROVISION,
+    TERMINATE
+  }
+
+  private static final Comparator<ScalingEvent> comparator = new Comparator<ScalingEvent>()
+
+  {
+    @Override
+    public int compare(ScalingEvent s1, ScalingEvent s2)
+    {
+      return -s1.getTimestamp().compareTo(s2.getTimestamp());
+    }
+  };
+
+  private final MinMaxPriorityQueue<ScalingEvent> recentNodes;
+
+  public ScalingStats(int capacity)
+  {
+    this.recentNodes = MinMaxPriorityQueue
+        .orderedBy(comparator)
+        .maximumSize(capacity)
+        .create();
+  }
+
+  public void addProvisionEvent(AutoScalingData data)
+  {
+    recentNodes.add(
+        new ScalingEvent(
+            data,
+            new DateTime(),
+            EVENT.PROVISION
+        )
+    );
+  }
+
+  public void addTerminateEvent(AutoScalingData data)
+  {
+    recentNodes.add(
+        new ScalingEvent(
+            data,
+            new DateTime(),
+            EVENT.TERMINATE
+        )
+    );
+  }
+
+  public List<ScalingEvent> toList()
+  {
+    List<ScalingEvent> retVal = Lists.newArrayList(recentNodes);
+    Collections.sort(retVal, comparator);
+    return retVal;
+  }
+
+  public static class ScalingEvent
+  {
+    private final AutoScalingData data;
+    private final DateTime timestamp;
+    private final EVENT event;
+
+    private ScalingEvent(
+        AutoScalingData data,
+        DateTime timestamp,
+        EVENT event
+    )
+    {
+      this.data = data;
+      this.timestamp = timestamp;
+      this.event = event;
+    }
+
+    public AutoScalingData getData()
+    {
+      return data;
+    }
+
+    public DateTime getTimestamp()
+    {
+      return timestamp;
+    }
+
+    public EVENT getEvent()
+    {
+      return event;
+    }
+
+    @Override
+    public String toString()
+    {
+      return "ScalingEvent{" +
+             "data=" + data +
+             ", timestamp=" + timestamp +
+             ", event=" + event +
+             '}';
+    }
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/SimpleResourceManagementStrategy.java

@@ -0,0 +1,233 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator.scaling;
+
+import com.google.common.base.Function;
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import com.metamx.common.guava.FunctionalIterable;
+import com.metamx.druid.merger.coordinator.TaskRunnerWorkItem;
+import com.metamx.druid.merger.coordinator.ZkWorker;
+import com.metamx.druid.merger.coordinator.setup.WorkerSetupManager;
+import com.metamx.emitter.EmittingLogger;
+import org.joda.time.DateTime;
+import org.joda.time.Duration;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.ConcurrentSkipListSet;
+
+/**
+ */
+public class SimpleResourceManagementStrategy implements ResourceManagementStrategy
+{
+  private static final EmittingLogger log = new EmittingLogger(SimpleResourceManagementStrategy.class);
+
+  private final AutoScalingStrategy autoScalingStrategy;
+  private final SimpleResourceManagmentConfig config;
+  private final WorkerSetupManager workerSetupManager;
+  private final ScalingStats scalingStats;
+
+  private final ConcurrentSkipListSet<String> currentlyProvisioning = new ConcurrentSkipListSet<String>();
+  private final ConcurrentSkipListSet<String> currentlyTerminating = new ConcurrentSkipListSet<String>();
+
+  private volatile DateTime lastProvisionTime = new DateTime();
+  private volatile DateTime lastTerminateTime = new DateTime();
+
+  public SimpleResourceManagementStrategy(
+      AutoScalingStrategy autoScalingStrategy,
+      SimpleResourceManagmentConfig config,
+      WorkerSetupManager workerSetupManager
+  )
+  {
+    this.autoScalingStrategy = autoScalingStrategy;
+    this.config = config;
+    this.workerSetupManager = workerSetupManager;
+    this.scalingStats = new ScalingStats(config.getNumEventsToTrack());
+  }
+
+  @Override
+  public boolean doProvision(Collection<TaskRunnerWorkItem> pendingTasks, Collection<ZkWorker> zkWorkers)
+  {
+    List<String> workerNodeIds = autoScalingStrategy.ipToIdLookup(
+        Lists.newArrayList(
+            Iterables.transform(
+                zkWorkers,
+                new Function<ZkWorker, String>()
+                {
+                  @Override
+                  public String apply(ZkWorker input)
+                  {
+                    return input.getWorker().getIp();
+                  }
+                }
+            )
+        )
+    );
+
+    for (String workerNodeId : workerNodeIds) {
+      currentlyProvisioning.remove(workerNodeId);
+    }
+
+    boolean nothingProvisioning = currentlyProvisioning.isEmpty();
+
+    if (nothingProvisioning) {
+      if (hasTaskPendingBeyondThreshold(pendingTasks)) {
+        AutoScalingData provisioned = autoScalingStrategy.provision();
+
+        if (provisioned != null) {
+          currentlyProvisioning.addAll(provisioned.getNodeIds());
+          lastProvisionTime = new DateTime();
+          scalingStats.addProvisionEvent(provisioned);
+
+          return true;
+        }
+      }
+    } else {
+      Duration durSinceLastProvision = new Duration(new DateTime(), lastProvisionTime);
+      if (durSinceLastProvision.isLongerThan(config.getMaxScalingDuration())) {
+        log.makeAlert("Worker node provisioning taking too long")
+           .addData("millisSinceLastProvision", durSinceLastProvision.getMillis())
+           .addData("provisioningCount", currentlyProvisioning.size())
+           .emit();
+      }
+
+      log.info(
+          "%s still provisioning. Wait for all provisioned nodes to complete before requesting new worker.",
+          currentlyProvisioning
+      );
+    }
+
+    return false;
+  }
+
+  @Override
+  public boolean doTerminate(Collection<TaskRunnerWorkItem> pendingTasks, Collection<ZkWorker> zkWorkers)
+  {
+    List<String> workerNodeIds = autoScalingStrategy.ipToIdLookup(
+        Lists.newArrayList(
+            Iterables.transform(
+                zkWorkers,
+                new Function<ZkWorker, String>()
+                {
+                  @Override
+                  public String apply(ZkWorker input)
+                  {
+                    return input.getWorker().getIp();
+                  }
+                }
+            )
+        )
+    );
+
+    for (String workerNodeId : workerNodeIds) {
+      currentlyTerminating.remove(workerNodeId);
+    }
+
+    boolean nothingTerminating = currentlyTerminating.isEmpty();
+
+    if (nothingTerminating) {
+      final int minNumWorkers = workerSetupManager.getWorkerSetupData().getMinNumWorkers();
+      if (zkWorkers.size() <= minNumWorkers) {
+        return false;
+      }
+
+      List<ZkWorker> thoseLazyWorkers = Lists.newArrayList(
+          FunctionalIterable
+              .create(zkWorkers)
+              .filter(
+                  new Predicate<ZkWorker>()
+                  {
+                    @Override
+                    public boolean apply(ZkWorker input)
+                    {
+                      return input.getRunningTasks().isEmpty()
+                             && System.currentTimeMillis() - input.getLastCompletedTaskTime().getMillis()
+                                >= config.getMaxWorkerIdleTimeMillisBeforeDeletion();
+                    }
+                  }
+              )
+      );
+
+      if (thoseLazyWorkers.isEmpty()) {
+        return false;
+      }
+
+      AutoScalingData terminated = autoScalingStrategy.terminate(
+          Lists.transform(
+              thoseLazyWorkers.subList(minNumWorkers, thoseLazyWorkers.size() - 1),
+              new Function<ZkWorker, String>()
+              {
+                @Override
+                public String apply(ZkWorker input)
+                {
+                  return input.getWorker().getIp();
+                }
+              }
+          )
+      );
+
+      if (terminated != null) {
+        currentlyTerminating.addAll(terminated.getNodeIds());
+        lastTerminateTime = new DateTime();
+        scalingStats.addTerminateEvent(terminated);
+
+        return true;
+      }
+    } else {
+      Duration durSinceLastTerminate = new Duration(new DateTime(), lastTerminateTime);
+      if (durSinceLastTerminate.isLongerThan(config.getMaxScalingDuration())) {
+        log.makeAlert("Worker node termination taking too long")
+           .addData("millisSinceLastTerminate", durSinceLastTerminate.getMillis())
+           .addData("terminatingCount", currentlyTerminating.size())
+           .emit();
+      }
+
+      log.info(
+          "%s still terminating. Wait for all nodes to terminate before trying again.",
+          currentlyTerminating
+      );
+    }
+
+    return false;
+  }
+
+  @Override
+  public ScalingStats getStats()
+  {
+    return scalingStats;
+  }
+
+  private boolean hasTaskPendingBeyondThreshold(Collection<TaskRunnerWorkItem> pendingTasks)
+  {
+    long now = System.currentTimeMillis();
+    for (TaskRunnerWorkItem pendingTask : pendingTasks) {
+      if (new Duration(pendingTask.getQueueInsertionTime().getMillis(), now).isEqual(config.getMaxPendingTaskDuration())
+          ||
+          new Duration(
+              pendingTask.getQueueInsertionTime().getMillis(), now
+          ).isLongerThan(config.getMaxPendingTaskDuration())) {
+        return true;
+      }
+    }
+    return false;
+  }
+}

merger/src/main/java/com/metamx/druid/merger/coordinator/scaling/SimpleResourceManagmentConfig.java

@@ -0,0 +1,45 @@
+/*
+ * Druid - a distributed column store.
+ * Copyright (C) 2012  Metamarkets Group Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+package com.metamx.druid.merger.coordinator.scaling;
+
+import org.joda.time.Duration;
+import org.skife.config.Config;
+import org.skife.config.Default;
+
+/**
+ */
+public abstract class SimpleResourceManagmentConfig
+{
+  @Config("druid.indexer.maxWorkerIdleTimeMillisBeforeDeletion")
+  @Default("600000")
+  public abstract int getMaxWorkerIdleTimeMillisBeforeDeletion();
+
+  @Config("druid.indexer.maxScalingDuration")
+  @Default("PT15M")
+  public abstract Duration getMaxScalingDuration();
+
+  @Config("druid.indexer.numEventsToTrack")
+  @Default("50")
+  public abstract int getNumEventsToTrack();
+
+  @Config("druid.indexer.maxPendingTaskDuration")
+  @Default("PT30S")
+  public abstract Duration getMaxPendingTaskDuration();
+}