Allow reordered segment allocation in kafka indexing service (#5805)

* Allow reordered segment allocation in kafka indexing service

* address comments

* fix a bug

indexing-service/src/test/java/io/druid/indexing/common/task/IndexTaskTest.java

@@ -450,12 +450,12 @@ public class IndexTaskTest
 
     Assert.assertEquals("test", segments.get(0).getDataSource());
     Assert.assertEquals(Intervals.of("2014/P1D"), segments.get(0).getInterval());
-    Assert.assertTrue(segments.get(0).getShardSpec().getClass().equals(NumberedShardSpec.class));
+    Assert.assertEquals(NumberedShardSpec.class, segments.get(0).getShardSpec().getClass());
     Assert.assertEquals(0, segments.get(0).getShardSpec().getPartitionNum());
 
     Assert.assertEquals("test", segments.get(1).getDataSource());
     Assert.assertEquals(Intervals.of("2014/P1D"), segments.get(1).getInterval());
-    Assert.assertTrue(segments.get(1).getShardSpec().getClass().equals(NumberedShardSpec.class));
+    Assert.assertEquals(NumberedShardSpec.class, segments.get(1).getShardSpec().getClass());
     Assert.assertEquals(1, segments.get(1).getShardSpec().getPartitionNum());
   }
 

java-util/src/main/java/io/druid/java/util/common/Pair.java

@@ -19,6 +19,7 @@
 
 package io.druid.java.util.common;
 
+import javax.annotation.Nullable;
 import java.util.Objects;
 
 /**
@@ -26,18 +27,20 @@ import java.util.Objects;
 public class Pair<T1, T2>
 {
 
-  public static <T1, T2> Pair<T1, T2> of(T1 lhs, T2 rhs)
+  public static <T1, T2> Pair<T1, T2> of(@Nullable T1 lhs, @Nullable T2 rhs)
   {
     return new Pair<>(lhs, rhs);
   }
 
+  @Nullable
   public final T1 lhs;
 
+  @Nullable
   public final T2 rhs;
 
   public Pair(
-      T1 lhs,
+      @Nullable T1 lhs,
-      T2 rhs
+      @Nullable T2 rhs
   )
   {
     this.lhs = lhs;

server/src/main/java/io/druid/metadata/IndexerSQLMetadataStorageCoordinator.java

@@ -19,6 +19,7 @@
 
 package io.druid.metadata;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.base.Function;
 import com.google.common.base.Preconditions;
@@ -66,6 +67,7 @@ import org.skife.jdbi.v2.tweak.ResultSetMapper;
 import org.skife.jdbi.v2.util.ByteArrayMapper;
 import org.skife.jdbi.v2.util.StringMapper;
 
+import javax.annotation.Nullable;
 import java.io.IOException;
 import java.sql.ResultSet;
 import java.sql.SQLException;
@@ -131,7 +133,7 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
         new HandleCallback<List<DataSegment>>()
         {
           @Override
-          public List<DataSegment> withHandle(Handle handle) throws Exception
+          public List<DataSegment> withHandle(Handle handle)
           {
             final VersionedIntervalTimeline<String, DataSegment> timeline = getTimelineForIntervalsWithHandle(
                 handle,
@@ -378,7 +380,7 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
   public SegmentIdentifier allocatePendingSegment(
       final String dataSource,
       final String sequenceName,
-      final String previousSegmentId,
+      @Nullable final String previousSegmentId,
       final Interval interval,
       final String maxVersion,
       final boolean skipSegmentLineageCheck
@@ -389,18 +391,42 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
     Preconditions.checkNotNull(interval, "interval");
     Preconditions.checkNotNull(maxVersion, "maxVersion");
 
-    final String previousSegmentIdNotNull = previousSegmentId == null ? "" : previousSegmentId;
-
     return connector.retryTransaction(
         new TransactionCallback<SegmentIdentifier>()
         {
           @Override
           public SegmentIdentifier inTransaction(Handle handle, TransactionStatus transactionStatus) throws Exception
           {
-            final List<byte[]> existingBytes;
+            return skipSegmentLineageCheck ?
-            if (!skipSegmentLineageCheck) {
+                   allocatePendingSegment(handle, dataSource, sequenceName, interval, maxVersion) :
-              existingBytes = handle
+                   allocatePendingSegmentWithSegmentLineageCheck(
-                  .createQuery(
+                       handle,
+                       dataSource,
+                       sequenceName,
+                       previousSegmentId,
+                       interval,
+                       maxVersion
+                   );
+          }
+        },
+        ALLOCATE_SEGMENT_QUIET_TRIES,
+        SQLMetadataConnector.DEFAULT_MAX_TRIES
+    );
+  }
+
+  @Nullable
+  private SegmentIdentifier allocatePendingSegmentWithSegmentLineageCheck(
+      final Handle handle,
+      final String dataSource,
+      final String sequenceName,
+      @Nullable final String previousSegmentId,
+      final Interval interval,
+      final String maxVersion
+  ) throws IOException
+  {
+    final String previousSegmentIdNotNull = previousSegmentId == null ? "" : previousSegmentId;
+    final CheckExistingSegmentIdResult result = checkAndGetExistingSegmentId(
+        handle.createQuery(
             StringUtils.format(
                 "SELECT payload FROM %s WHERE "
                 + "dataSource = :dataSource AND "
@@ -408,30 +434,138 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
                 + "sequence_prev_id = :sequence_prev_id",
                 dbTables.getPendingSegmentsTable()
             )
-                  ).bind("dataSource", dataSource)
+        ),
-                  .bind("sequence_name", sequenceName)
+        interval,
-                  .bind("sequence_prev_id", previousSegmentIdNotNull)
+        sequenceName,
-                  .map(ByteArrayMapper.FIRST)
+        previousSegmentIdNotNull,
-                  .list();
+        Pair.of("dataSource", dataSource),
-            } else {
+        Pair.of("sequence_name", sequenceName),
-              existingBytes = handle
+        Pair.of("sequence_prev_id", previousSegmentIdNotNull)
-                  .createQuery(
+    );
+
+    if (result.found) {
+      // The found existing segment identifier can be null if its interval doesn't match with the given interval
+      return result.segmentIdentifier;
+    }
+
+    final SegmentIdentifier newIdentifier = createNewSegment(handle, dataSource, interval, maxVersion);
+    if (newIdentifier == null) {
+      return null;
+    }
+
+    // SELECT -> INSERT can fail due to races; callers must be prepared to retry.
+    // Avoiding ON DUPLICATE KEY since it's not portable.
+    // Avoiding try/catch since it may cause inadvertent transaction-splitting.
+
+    // UNIQUE key for the row, ensuring sequences do not fork in two directions.
+    // Using a single column instead of (sequence_name, sequence_prev_id) as some MySQL storage engines
+    // have difficulty with large unique keys (see https://github.com/druid-io/druid/issues/2319)
+    final String sequenceNamePrevIdSha1 = BaseEncoding.base16().encode(
+        Hashing.sha1()
+               .newHasher()
+               .putBytes(StringUtils.toUtf8(sequenceName))
+               .putByte((byte) 0xff)
+               .putBytes(StringUtils.toUtf8(previousSegmentIdNotNull))
+               .hash()
+               .asBytes()
+    );
+
+    insertToMetastore(
+        handle,
+        newIdentifier,
+        dataSource,
+        interval,
+        previousSegmentIdNotNull,
+        sequenceName,
+        sequenceNamePrevIdSha1
+    );
+    return newIdentifier;
+  }
+
+  @Nullable
+  private SegmentIdentifier allocatePendingSegment(
+      final Handle handle,
+      final String dataSource,
+      final String sequenceName,
+      final Interval interval,
+      final String maxVersion
+  ) throws IOException
+  {
+    final CheckExistingSegmentIdResult result = checkAndGetExistingSegmentId(
+        handle.createQuery(
             StringUtils.format(
                 "SELECT payload FROM %s WHERE "
                 + "dataSource = :dataSource AND "
                 + "sequence_name = :sequence_name AND "
                 + "start = :start AND "
                 + "%2$send%2$s = :end",
-                          dbTables.getPendingSegmentsTable(), connector.getQuoteString()
+                dbTables.getPendingSegmentsTable(),
+                connector.getQuoteString()
             )
-                  ).bind("dataSource", dataSource)
+        ),
-                  .bind("sequence_name", sequenceName)
+        interval,
-                  .bind("start", interval.getStart().toString())
+        sequenceName,
-                  .bind("end", interval.getEnd().toString())
+        null,
-                  .map(ByteArrayMapper.FIRST)
+        Pair.of("dataSource", dataSource),
-                  .list();
+        Pair.of("sequence_name", sequenceName),
+        Pair.of("start", interval.getStart().toString()),
+        Pair.of("end", interval.getEnd().toString())
+    );
+
+    if (result.found) {
+      // The found existing segment identifier can be null if its interval doesn't match with the given interval
+      return result.segmentIdentifier;
     }
 
+    final SegmentIdentifier newIdentifier = createNewSegment(handle, dataSource, interval, maxVersion);
+    if (newIdentifier == null) {
+      return null;
+    }
+
+    // SELECT -> INSERT can fail due to races; callers must be prepared to retry.
+    // Avoiding ON DUPLICATE KEY since it's not portable.
+    // Avoiding try/catch since it may cause inadvertent transaction-splitting.
+
+    // UNIQUE key for the row, ensuring we don't have more than one segment per sequence per interval.
+    // Using a single column instead of (sequence_name, sequence_prev_id) as some MySQL storage engines
+    // have difficulty with large unique keys (see https://github.com/druid-io/druid/issues/2319)
+    final String sequenceNamePrevIdSha1 = BaseEncoding.base16().encode(
+        Hashing.sha1()
+               .newHasher()
+               .putBytes(StringUtils.toUtf8(sequenceName))
+               .putByte((byte) 0xff)
+               .putLong(interval.getStartMillis())
+               .putLong(interval.getEndMillis())
+               .hash()
+               .asBytes()
+    );
+
+    // always insert empty previous sequence id
+    insertToMetastore(handle, newIdentifier, dataSource, interval, "", sequenceName, sequenceNamePrevIdSha1);
+
+    log.info(
+        "Allocated pending segment [%s] for sequence[%s] in DB",
+        newIdentifier.getIdentifierAsString(),
+        sequenceName
+    );
+
+    return newIdentifier;
+  }
+
+  private CheckExistingSegmentIdResult checkAndGetExistingSegmentId(
+      final Query<Map<String, Object>> query,
+      final Interval interval,
+      final String sequenceName,
+      final @Nullable String previousSegmentId,
+      final Pair<String, String>... queryVars
+  ) throws IOException
+  {
+    Query<Map<String, Object>> boundQuery = query;
+    for (Pair<String, String> var : queryVars) {
+      boundQuery = boundQuery.bind(var.lhs, var.rhs);
+    }
+    final List<byte[]> existingBytes = boundQuery.map(ByteArrayMapper.FIRST).list();
+
     if (!existingBytes.isEmpty()) {
       final SegmentIdentifier existingIdentifier = jsonMapper.readValue(
           Iterables.getOnlyElement(existingBytes),
@@ -440,34 +574,103 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
 
       if (existingIdentifier.getInterval().getStartMillis() == interval.getStartMillis()
           && existingIdentifier.getInterval().getEndMillis() == interval.getEndMillis()) {
+        if (previousSegmentId == null) {
+          log.info(
+              "Found existing pending segment [%s] for sequence[%s] in DB",
+              existingIdentifier.getIdentifierAsString(),
+              sequenceName
+          );
+        } else {
           log.info(
               "Found existing pending segment [%s] for sequence[%s] (previous = [%s]) in DB",
               existingIdentifier.getIdentifierAsString(),
               sequenceName,
-                    previousSegmentIdNotNull
+              previousSegmentId
           );
+        }
 
-                return existingIdentifier;
+        return new CheckExistingSegmentIdResult(true, existingIdentifier);
+      } else {
+        if (previousSegmentId == null) {
+          log.warn(
+              "Cannot use existing pending segment [%s] for sequence[%s] in DB, "
+              + "does not match requested interval[%s]",
+              existingIdentifier.getIdentifierAsString(),
+              sequenceName,
+              interval
+          );
         } else {
           log.warn(
               "Cannot use existing pending segment [%s] for sequence[%s] (previous = [%s]) in DB, "
               + "does not match requested interval[%s]",
               existingIdentifier.getIdentifierAsString(),
               sequenceName,
-                    previousSegmentIdNotNull,
+              previousSegmentId,
               interval
           );
+        }
 
-                return null;
+        return new CheckExistingSegmentIdResult(true, null);
+      }
+    }
+    return new CheckExistingSegmentIdResult(false, null);
+  }
+
+  private static class CheckExistingSegmentIdResult
+  {
+    private final boolean found;
+    @Nullable
+    private final SegmentIdentifier segmentIdentifier;
+
+    CheckExistingSegmentIdResult(boolean found, @Nullable SegmentIdentifier segmentIdentifier)
+    {
+      this.found = found;
+      this.segmentIdentifier = segmentIdentifier;
     }
   }
 
+  private void insertToMetastore(
+      Handle handle,
+      SegmentIdentifier newIdentifier,
+      String dataSource,
+      Interval interval,
+      String previousSegmentId,
+      String sequenceName,
+      String sequenceNamePrevIdSha1
+  ) throws JsonProcessingException
+  {
+    handle.createStatement(
+        StringUtils.format(
+            "INSERT INTO %1$s (id, dataSource, created_date, start, %2$send%2$s, sequence_name, sequence_prev_id, sequence_name_prev_id_sha1, payload) "
+            + "VALUES (:id, :dataSource, :created_date, :start, :end, :sequence_name, :sequence_prev_id, :sequence_name_prev_id_sha1, :payload)",
+            dbTables.getPendingSegmentsTable(),
+            connector.getQuoteString()
+        )
+    )
+          .bind("id", newIdentifier.getIdentifierAsString())
+          .bind("dataSource", dataSource)
+          .bind("created_date", DateTimes.nowUtc().toString())
+          .bind("start", interval.getStart().toString())
+          .bind("end", interval.getEnd().toString())
+          .bind("sequence_name", sequenceName)
+          .bind("sequence_prev_id", previousSegmentId)
+          .bind("sequence_name_prev_id_sha1", sequenceNamePrevIdSha1)
+          .bind("payload", jsonMapper.writeValueAsBytes(newIdentifier))
+          .execute();
+  }
+
+  @Nullable
+  private SegmentIdentifier createNewSegment(
+      final Handle handle,
+      final String dataSource,
+      final Interval interval,
+      final String maxVersion
+  ) throws IOException
+  {
     // Make up a pending segment based on existing segments and pending segments in the DB. This works
     // assuming that all tasks inserting segments at a particular point in time are going through the
     // allocatePendingSegment flow. This should be assured through some other mechanism (like task locks).
 
-            final SegmentIdentifier newIdentifier;
-
     final List<TimelineObjectHolder<String, DataSegment>> existingChunks = getTimelineForIntervalsWithHandle(
         handle,
         dataSource,
@@ -514,7 +717,7 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
       }
 
       if (max == null) {
-                newIdentifier = new SegmentIdentifier(
+        return new SegmentIdentifier(
             dataSource,
             interval,
             maxVersion,
@@ -530,14 +733,14 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
         );
         return null;
       } else if (max.getShardSpec() instanceof LinearShardSpec) {
-                newIdentifier = new SegmentIdentifier(
+        return new SegmentIdentifier(
             dataSource,
             max.getInterval(),
             max.getVersion(),
             new LinearShardSpec(max.getShardSpec().getPartitionNum() + 1)
         );
       } else if (max.getShardSpec() instanceof NumberedShardSpec) {
-                newIdentifier = new SegmentIdentifier(
+        return new SegmentIdentifier(
             dataSource,
             max.getInterval(),
             max.getVersion(),
@@ -558,56 +761,6 @@ public class IndexerSQLMetadataStorageCoordinator implements IndexerMetadataStor
         return null;
       }
     }
-
-            // SELECT -> INSERT can fail due to races; callers must be prepared to retry.
-            // Avoiding ON DUPLICATE KEY since it's not portable.
-            // Avoiding try/catch since it may cause inadvertent transaction-splitting.
-
-            // UNIQUE key for the row, ensuring sequences do not fork in two directions.
-            // Using a single column instead of (sequence_name, sequence_prev_id) as some MySQL storage engines
-            // have difficulty with large unique keys (see https://github.com/druid-io/druid/issues/2319)
-            final String sequenceNamePrevIdSha1 = BaseEncoding.base16().encode(
-                Hashing.sha1()
-                       .newHasher()
-                       .putBytes(StringUtils.toUtf8(sequenceName))
-                       .putByte((byte) 0xff)
-                       .putBytes(StringUtils.toUtf8(previousSegmentIdNotNull))
-                       .hash()
-                       .asBytes()
-            );
-
-            handle.createStatement(
-                StringUtils.format(
-                    "INSERT INTO %1$s (id, dataSource, created_date, start, %2$send%2$s, sequence_name, sequence_prev_id, sequence_name_prev_id_sha1, payload) "
-                    + "VALUES (:id, :dataSource, :created_date, :start, :end, :sequence_name, :sequence_prev_id, :sequence_name_prev_id_sha1, :payload)",
-                    dbTables.getPendingSegmentsTable(),
-                    connector.getQuoteString()
-                )
-            )
-                  .bind("id", newIdentifier.getIdentifierAsString())
-                  .bind("dataSource", dataSource)
-                  .bind("created_date", DateTimes.nowUtc().toString())
-                  .bind("start", interval.getStart().toString())
-                  .bind("end", interval.getEnd().toString())
-                  .bind("sequence_name", sequenceName)
-                  .bind("sequence_prev_id", previousSegmentIdNotNull)
-                  .bind("sequence_name_prev_id_sha1", sequenceNamePrevIdSha1)
-                  .bind("payload", jsonMapper.writeValueAsBytes(newIdentifier))
-                  .execute();
-
-            log.info(
-                "Allocated pending segment [%s] for sequence[%s] (previous = [%s]) in DB",
-                newIdentifier.getIdentifierAsString(),
-                sequenceName,
-                previousSegmentIdNotNull
-            );
-
-            return newIdentifier;
-          }
-        },
-        ALLOCATE_SEGMENT_QUIET_TRIES,
-        SQLMetadataConnector.DEFAULT_MAX_TRIES
-    );
   }
 
   @Override

server/src/main/java/io/druid/segment/realtime/appenderator/BaseAppenderatorDriver.java

@@ -42,12 +42,13 @@ import io.druid.java.util.common.logger.Logger;
 import io.druid.segment.loading.DataSegmentKiller;
 import io.druid.segment.realtime.appenderator.SegmentWithState.SegmentState;
 import org.joda.time.DateTime;
+import org.joda.time.Interval;
 
 import javax.annotation.Nullable;
 import java.io.Closeable;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Collection;
-import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -55,6 +56,7 @@ import java.util.NavigableMap;
 import java.util.Objects;
 import java.util.Set;
 import java.util.TreeMap;
+import java.util.function.Consumer;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -75,6 +77,94 @@ import java.util.stream.Stream;
  */
 public abstract class BaseAppenderatorDriver implements Closeable
 {
+  /**
+   * Segments allocated for an intervval.
+   * There should be at most a single active (appending) segment at any time.
+   */
+  static class SegmentsOfInterval
+  {
+    private final Interval interval;
+    private final List<SegmentWithState> appendFinishedSegments = new ArrayList<>();
+
+    @Nullable
+    private SegmentWithState appendingSegment;
+
+    SegmentsOfInterval(Interval interval)
+    {
+      this.interval = interval;
+    }
+
+    SegmentsOfInterval(
+        Interval interval,
+        @Nullable SegmentWithState appendingSegment,
+        List<SegmentWithState> appendFinishedSegments
+    )
+    {
+      this.interval = interval;
+      this.appendingSegment = appendingSegment;
+      this.appendFinishedSegments.addAll(appendFinishedSegments);
+
+      if (appendingSegment != null) {
+        Preconditions.checkArgument(
+            appendingSegment.getState() == SegmentState.APPENDING,
+            "appendingSegment[%s] is not in the APPENDING state",
+            appendingSegment.getSegmentIdentifier()
+        );
+      }
+      if (appendFinishedSegments
+          .stream()
+          .anyMatch(segmentWithState -> segmentWithState.getState() == SegmentState.APPENDING)) {
+        throw new ISE("Some appendFinishedSegments[%s] is in the APPENDING state", appendFinishedSegments);
+      }
+    }
+
+    void setAppendingSegment(SegmentWithState appendingSegment)
+    {
+      Preconditions.checkArgument(
+          appendingSegment.getState() == SegmentState.APPENDING,
+          "segment[%s] is not in the APPENDING state",
+          appendingSegment.getSegmentIdentifier()
+      );
+      // There should be only one appending segment at any time
+      Preconditions.checkState(
+          this.appendingSegment == null,
+          "WTF?! Current appendingSegment[%s] is not null. "
+          + "Its state must be changed before setting a new appendingSegment[%s]",
+          this.appendingSegment,
+          appendingSegment
+      );
+      this.appendingSegment = appendingSegment;
+    }
+
+    void finishAppendingToCurrentActiveSegment(Consumer<SegmentWithState> stateTransitionFn)
+    {
+      Preconditions.checkNotNull(appendingSegment, "appendingSegment");
+      stateTransitionFn.accept(appendingSegment);
+      appendFinishedSegments.add(appendingSegment);
+      appendingSegment = null;
+    }
+
+    Interval getInterval()
+    {
+      return interval;
+    }
+
+    SegmentWithState getAppendingSegment()
+    {
+      return appendingSegment;
+    }
+
+    List<SegmentWithState> getAllSegments()
+    {
+      final List<SegmentWithState> allSegments = new ArrayList<>(appendFinishedSegments.size() + 1);
+      if (appendingSegment != null) {
+        allSegments.add(appendingSegment);
+      }
+      allSegments.addAll(appendFinishedSegments);
+      return allSegments;
+    }
+  }
+
   /**
    * Allocated segments for a sequence
    */
@@ -83,7 +173,7 @@ public abstract class BaseAppenderatorDriver implements Closeable
     // Interval Start millis -> List of Segments for this interval
     // there might be multiple segments for a start interval, for example one segment
     // can be in APPENDING state and others might be in PUBLISHING state
-    private final NavigableMap<Long, LinkedList<SegmentWithState>> intervalToSegmentStates;
+    private final NavigableMap<Long, SegmentsOfInterval> intervalToSegmentStates;
 
     // most recently allocated segment
     private String lastSegmentId;
@@ -94,7 +184,7 @@ public abstract class BaseAppenderatorDriver implements Closeable
     }
 
     SegmentsForSequence(
-        NavigableMap<Long, LinkedList<SegmentWithState>> intervalToSegmentStates,
+        NavigableMap<Long, SegmentsOfInterval> intervalToSegmentStates,
         String lastSegmentId
     )
     {
@@ -104,24 +194,34 @@ public abstract class BaseAppenderatorDriver implements Closeable
 
     void add(SegmentIdentifier identifier)
     {
-      intervalToSegmentStates.computeIfAbsent(identifier.getInterval().getStartMillis(), k -> new LinkedList<>())
+      intervalToSegmentStates.computeIfAbsent(
-                             .addFirst(SegmentWithState.newSegment(identifier));
+          identifier.getInterval().getStartMillis(),
+          k -> new SegmentsOfInterval(identifier.getInterval())
+      ).setAppendingSegment(SegmentWithState.newSegment(identifier));
       lastSegmentId = identifier.getIdentifierAsString();
     }
 
-    Entry<Long, LinkedList<SegmentWithState>> floor(long timestamp)
+    Entry<Long, SegmentsOfInterval> floor(long timestamp)
     {
       return intervalToSegmentStates.floorEntry(timestamp);
     }
 
-    LinkedList<SegmentWithState> get(long timestamp)
+    SegmentsOfInterval get(long timestamp)
     {
       return intervalToSegmentStates.get(timestamp);
     }
 
-    Stream<SegmentWithState> segmentStateStream()
+    Stream<SegmentWithState> allSegmentStateStream()
     {
-      return intervalToSegmentStates.values().stream().flatMap(Collection::stream);
+      return intervalToSegmentStates
+          .values()
+          .stream()
+          .flatMap(segmentsOfInterval -> segmentsOfInterval.getAllSegments().stream());
+    }
+
+    Stream<SegmentsOfInterval> getAllSegmentsOfInterval()
+    {
+      return intervalToSegmentStates.values().stream();
     }
   }
 
@@ -183,13 +283,19 @@ public abstract class BaseAppenderatorDriver implements Closeable
         return null;
       }
 
-      final Map.Entry<Long, LinkedList<SegmentWithState>> candidateEntry = segmentsForSequence.floor(
+      final Map.Entry<Long, SegmentsOfInterval> candidateEntry = segmentsForSequence.floor(
           timestamp.getMillis()
       );
-      if (candidateEntry != null
+
-          && candidateEntry.getValue().getFirst().getSegmentIdentifier().getInterval().contains(timestamp)
+      if (candidateEntry != null) {
-          && candidateEntry.getValue().getFirst().getState() == SegmentState.APPENDING) {
+        final SegmentsOfInterval segmentsOfInterval = candidateEntry.getValue();
-        return candidateEntry.getValue().getFirst().getSegmentIdentifier();
+        if (segmentsOfInterval.interval.contains(timestamp)) {
+          return segmentsOfInterval.appendingSegment == null ?
+                 null :
+                 segmentsOfInterval.appendingSegment.getSegmentIdentifier();
+        } else {
+          return null;
+        }
       } else {
         return null;
       }
@@ -327,7 +433,20 @@ public abstract class BaseAppenderatorDriver implements Closeable
           .map(segments::get)
           .filter(Objects::nonNull)
           .flatMap(segmentsForSequence -> segmentsForSequence.intervalToSegmentStates.values().stream())
-          .flatMap(Collection::stream);
+          .flatMap(segmentsOfInterval -> segmentsOfInterval.getAllSegments().stream());
+    }
+  }
+
+  Stream<SegmentWithState> getAppendingSegments(Collection<String> sequenceNames)
+  {
+    synchronized (segments) {
+      return sequenceNames
+          .stream()
+          .map(segments::get)
+          .filter(Objects::nonNull)
+          .flatMap(segmentsForSequence -> segmentsForSequence.intervalToSegmentStates.values().stream())
+          .map(segmentsOfInterval -> segmentsOfInterval.appendingSegment)
+          .filter(Objects::nonNull);
     }
   }
 
@@ -538,9 +657,10 @@ public abstract class BaseAppenderatorDriver implements Closeable
             Maps.transformValues(
                 snapshot,
                 (Function<SegmentsForSequence, List<SegmentWithState>>) input -> ImmutableList.copyOf(
-                    input.intervalToSegmentStates.values()
+                    input.intervalToSegmentStates
+                        .values()
                         .stream()
-                                                 .flatMap(Collection::stream)
+                        .flatMap(segmentsOfInterval -> segmentsOfInterval.getAllSegments().stream())
                         .collect(Collectors.toList())
                 )
             )

server/src/main/java/io/druid/segment/realtime/appenderator/BatchAppenderatorDriver.java

@@ -33,11 +33,11 @@ import io.druid.timeline.DataSegment;
 import javax.annotation.Nullable;
 import java.io.IOException;
 import java.util.Collection;
-import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 /**
@@ -129,13 +129,11 @@ public class BatchAppenderatorDriver extends BaseAppenderatorDriver
       long pushAndClearTimeoutMs
   ) throws InterruptedException, ExecutionException, TimeoutException
   {
-    final List<SegmentIdentifier> segmentIdentifierList = getSegmentWithStates(sequenceNames)
+    final Map<SegmentIdentifier, SegmentWithState> requestedSegmentIdsForSequences = getAppendingSegments(sequenceNames)
-        .filter(segmentWithState -> segmentWithState.getState() == SegmentState.APPENDING)
+        .collect(Collectors.toMap(SegmentWithState::getSegmentIdentifier, Function.identity()));
-        .map(SegmentWithState::getSegmentIdentifier)
-        .collect(Collectors.toList());
 
     final ListenableFuture<SegmentsAndMetadata> future = ListenableFutures.transformAsync(
-        pushInBackground(null, segmentIdentifierList, false),
+        pushInBackground(null, requestedSegmentIdsForSequences.keySet(), false),
         this::dropInBackground
     );
 
@@ -147,17 +145,7 @@ public class BatchAppenderatorDriver extends BaseAppenderatorDriver
     final Map<SegmentIdentifier, DataSegment> pushedSegmentIdToSegmentMap = segmentsAndMetadata
         .getSegments()
         .stream()
-        .collect(Collectors.toMap(
+        .collect(Collectors.toMap(SegmentIdentifier::fromDataSegment, Function.identity()));
-            SegmentIdentifier::fromDataSegment,
-            dataSegment -> dataSegment
-        ));
-
-    final Map<SegmentIdentifier, SegmentWithState> requestedSegmentIdsForSequences = getSegmentWithStates(sequenceNames)
-        .filter(segmentWithState -> segmentWithState.getState() == SegmentState.APPENDING)
-        .collect(Collectors.toMap(
-            SegmentWithState::getSegmentIdentifier,
-            segmentWithState -> segmentWithState
-        ));
 
     if (!pushedSegmentIdToSegmentMap.keySet().equals(requestedSegmentIdsForSequences.keySet())) {
       throw new ISE(
@@ -167,12 +155,28 @@ public class BatchAppenderatorDriver extends BaseAppenderatorDriver
       );
     }
 
-    // State transition
+    synchronized (segments) {
-    requestedSegmentIdsForSequences.forEach(
+      for (String sequenceName : sequenceNames) {
-        (segmentId, segmentWithState) -> {
+        final SegmentsForSequence segmentsForSequence = segments.get(sequenceName);
-          segmentWithState.pushAndDrop(pushedSegmentIdToSegmentMap.get(segmentId));
+        if (segmentsForSequence == null) {
+          throw new ISE("Can't find segmentsForSequence for sequence[%s]", sequenceName);
         }
+
+        segmentsForSequence.getAllSegmentsOfInterval().forEach(segmentsOfInterval -> {
+          final SegmentWithState appendingSegment = segmentsOfInterval.getAppendingSegment();
+          if (appendingSegment != null) {
+            final DataSegment pushedSegment = pushedSegmentIdToSegmentMap.get(appendingSegment.getSegmentIdentifier());
+            if (pushedSegment == null) {
+              throw new ISE("Can't find pushedSegments for segment[%s]", appendingSegment.getSegmentIdentifier());
+            }
+
+            segmentsOfInterval.finishAppendingToCurrentActiveSegment(
+                segmentWithState -> segmentWithState.pushAndDrop(pushedSegment)
             );
+          }
+        });
+      }
+    }
 
     return segmentsAndMetadata;
   }
@@ -196,7 +200,7 @@ public class BatchAppenderatorDriver extends BaseAppenderatorDriver
             snapshot
                 .values()
                 .stream()
-                .flatMap(SegmentsForSequence::segmentStateStream)
+                .flatMap(SegmentsForSequence::allSegmentStateStream)
                 .map(segmentWithState -> Preconditions
                     .checkNotNull(
                         segmentWithState.getDataSegment(),

server/src/main/java/io/druid/segment/realtime/appenderator/StreamAppenderatorDriver.java

@@ -32,7 +32,9 @@ import com.google.common.util.concurrent.SettableFuture;
 import io.druid.data.input.Committer;
 import io.druid.data.input.InputRow;
 import io.druid.java.util.common.ISE;
+import io.druid.java.util.common.Pair;
 import io.druid.java.util.common.concurrent.ListenableFutures;
+import io.druid.java.util.common.guava.Comparators;
 import io.druid.java.util.common.logger.Logger;
 import io.druid.query.SegmentDescriptor;
 import io.druid.segment.loading.DataSegmentKiller;
@@ -43,8 +45,9 @@ import io.druid.segment.realtime.plumber.SegmentHandoffNotifierFactory;
 
 import javax.annotation.Nullable;
 import java.io.IOException;
+import java.util.ArrayList;
 import java.util.Collection;
-import java.util.LinkedList;
+import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -194,18 +197,13 @@ public class StreamAppenderatorDriver extends BaseAppenderatorDriver
       for (final SegmentIdentifier identifier : identifiers) {
         log.info("Moving segment[%s] out of active list.", identifier);
         final long key = identifier.getInterval().getStartMillis();
-        if (activeSegmentsForSequence.get(key) == null || activeSegmentsForSequence.get(key).stream().noneMatch(
+        final SegmentsOfInterval segmentsOfInterval = activeSegmentsForSequence.get(key);
-            segmentWithState -> {
+        if (segmentsOfInterval == null ||
-              if (segmentWithState.getSegmentIdentifier().equals(identifier)) {
+            segmentsOfInterval.getAppendingSegment() == null ||
-                segmentWithState.finishAppending();
+            !segmentsOfInterval.getAppendingSegment().getSegmentIdentifier().equals(identifier)) {
-                return true;
-              } else {
-                return false;
-              }
-            }
-        )) {
           throw new ISE("WTF?! Asked to remove segment[%s] that didn't exist...", identifier);
         }
+        segmentsOfInterval.finishAppendingToCurrentActiveSegment(SegmentWithState::finishAppending);
       }
     }
   }
@@ -396,33 +394,53 @@ public class StreamAppenderatorDriver extends BaseAppenderatorDriver
 
   private static class SegmentsForSequenceBuilder
   {
-    private final NavigableMap<Long, LinkedList<SegmentWithState>> intervalToSegmentStates;
+    // segmentId -> (appendingSegment, appendFinishedSegments)
+    private final NavigableMap<SegmentIdentifier, Pair<SegmentWithState, List<SegmentWithState>>> intervalToSegments =
+        new TreeMap<>(Comparator.comparing(SegmentIdentifier::getInterval, Comparators.intervalsByStartThenEnd()));
     private final String lastSegmentId;
 
     SegmentsForSequenceBuilder(String lastSegmentId)
     {
-      this.intervalToSegmentStates = new TreeMap<>();
       this.lastSegmentId = lastSegmentId;
     }
 
     void add(SegmentWithState segmentWithState)
     {
       final SegmentIdentifier identifier = segmentWithState.getSegmentIdentifier();
-      final LinkedList<SegmentWithState> segmentsInInterval = intervalToSegmentStates.computeIfAbsent(
+      final Pair<SegmentWithState, List<SegmentWithState>> pair = intervalToSegments.get(identifier);
-          identifier.getInterval().getStartMillis(),
+      final List<SegmentWithState> appendFinishedSegments = pair == null || pair.rhs == null ?
-          k -> new LinkedList<>()
+                                                            new ArrayList<>() :
-      );
+                                                            pair.rhs;
+
       // always keep APPENDING segments for an interval start millis in the front
       if (segmentWithState.getState() == SegmentState.APPENDING) {
-        segmentsInInterval.addFirst(segmentWithState);
+        if (pair != null && pair.lhs != null) {
+          throw new ISE(
+              "WTF?! there was already an appendingSegment[%s] before adding an appendingSegment[%s]",
+              pair.lhs,
+              segmentWithState
+          );
+        }
+
+        intervalToSegments.put(identifier, Pair.of(segmentWithState, appendFinishedSegments));
       } else {
-        segmentsInInterval.addLast(segmentWithState);
+        final SegmentWithState appendingSegment = pair == null ? null : pair.lhs;
+        appendFinishedSegments.add(segmentWithState);
+        intervalToSegments.put(identifier, Pair.of(appendingSegment, appendFinishedSegments));
       }
     }
 
     SegmentsForSequence build()
     {
-      return new SegmentsForSequence(intervalToSegmentStates, lastSegmentId);
+      final NavigableMap<Long, SegmentsOfInterval> map = new TreeMap<>();
+      for (Entry<SegmentIdentifier, Pair<SegmentWithState, List<SegmentWithState>>> entry :
+          intervalToSegments.entrySet()) {
+        map.put(
+            entry.getKey().getInterval().getStartMillis(),
+            new SegmentsOfInterval(entry.getKey().getInterval(), entry.getValue().lhs, entry.getValue().rhs)
+        );
+      }
+      return new SegmentsForSequence(map, lastSegmentId);
     }
   }
 }

server/src/test/java/io/druid/segment/realtime/appenderator/BatchAppenderatorDriverTest.java

@@ -185,7 +185,7 @@ public class BatchAppenderatorDriverTest extends EasyMockSupport
     final SegmentsForSequence segmentsForSequence = driver.getSegments().get("dummy");
     Assert.assertNotNull(segmentsForSequence);
     final List<SegmentWithState> segmentWithStates = segmentsForSequence
-        .segmentStateStream()
+        .allSegmentStateStream()
         .filter(segmentWithState -> segmentWithState.getState() == expectedState)
         .collect(Collectors.toList());