YARN-5739. Provide timeline reader API to list available timeline entity types for one application. Contributed by Li Lu.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase-tests/src/test/java/org/apache/hadoop/yarn/server/timelineservice/storage/DataGeneratorForTest.java

@@ -31,6 +31,7 @@
 import org.apache.hadoop.yarn.api.records.timelineservice.TimelineEvent;
 import org.apache.hadoop.yarn.api.records.timelineservice.TimelineMetric;
 import org.apache.hadoop.yarn.api.records.timelineservice.TimelineMetric.Type;
+import org.apache.hadoop.yarn.server.metrics.ApplicationMetricsConstants;
 
 final class DataGeneratorForTest {
   static void loadApps(HBaseTestingUtility util) throws IOException {
@@ -358,6 +359,46 @@ static void loadEntities(HBaseTestingUtility util) throws IOException {
     relatesTo3.put("container2", relatesToSet14);
     entity2.setRelatesToEntities(relatesTo3);
     te.addEntity(entity2);
+
+    // For listing types
+    for (int i = 0; i < 10; i++) {
+      TimelineEntity entity3 = new TimelineEntity();
+      String id3 = "typeTest" + i;
+      entity3.setId(id3);
+      StringBuilder typeName = new StringBuilder("newType");
+      for (int j = 0; j < (i % 3); j++) {
+        typeName.append(" ").append(j);
+      }
+      entity3.setType(typeName.toString());
+      entity3.setCreatedTime(cTime + 80L + i);
+      te.addEntity(entity3);
+    }
+
+    // Create app entity for app to flow table
+    TimelineEntities appTe1 = new TimelineEntities();
+    TimelineEntity entityApp1 = new TimelineEntity();
+    String appName1 = "application_1231111111_1111";
+    entityApp1.setId(appName1);
+    entityApp1.setType(TimelineEntityType.YARN_APPLICATION.toString());
+    entityApp1.setCreatedTime(cTime + 40L);
+    TimelineEvent appCreationEvent1 = new TimelineEvent();
+    appCreationEvent1.setId(ApplicationMetricsConstants.CREATED_EVENT_TYPE);
+    appCreationEvent1.setTimestamp(cTime);
+    entityApp1.addEvent(appCreationEvent1);
+    appTe1.addEntity(entityApp1);
+
+    TimelineEntities appTe2 = new TimelineEntities();
+    TimelineEntity entityApp2 = new TimelineEntity();
+    String appName2 = "application_1231111111_1112";
+    entityApp2.setId(appName2);
+    entityApp2.setType(TimelineEntityType.YARN_APPLICATION.toString());
+    entityApp2.setCreatedTime(cTime + 50L);
+    TimelineEvent appCreationEvent2 = new TimelineEvent();
+    appCreationEvent2.setId(ApplicationMetricsConstants.CREATED_EVENT_TYPE);
+    appCreationEvent2.setTimestamp(cTime);
+    entityApp2.addEvent(appCreationEvent2);
+    appTe2.addEntity(entityApp2);
+
     HBaseTimelineWriterImpl hbi = null;
     try {
       hbi = new HBaseTimelineWriterImpl();
@@ -368,8 +409,10 @@ static void loadEntities(HBaseTestingUtility util) throws IOException {
       String flow = "some_flow_name";
       String flowVersion = "AB7822C10F1111";
       long runid = 1002345678919L;
-      String appName = "application_1231111111_1111";
+      hbi.write(cluster, user, flow, flowVersion, runid, appName1, te);
-      hbi.write(cluster, user, flow, flowVersion, runid, appName, te);
+      hbi.write(cluster, user, flow, flowVersion, runid, appName2, te);
+      hbi.write(cluster, user, flow, flowVersion, runid, appName1, appTe1);
+      hbi.write(cluster, user, flow, flowVersion, runid, appName2, appTe2);
       hbi.stop();
     } finally {
       if (hbi != null) {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase-tests/src/test/java/org/apache/hadoop/yarn/server/timelineservice/storage/TestHBaseTimelineStorageEntities.java

@@ -1672,6 +1672,29 @@ public void testReadEntitiesInfoFilters() throws Exception {
     assertEquals(3, entities.size());
   }
 
+  @Test(timeout = 90000)
+  public void testListTypesInApp() throws Exception {
+    Set<String> types = reader.getEntityTypes(
+        new TimelineReaderContext("cluster1", "user1", "some_flow_name",
+            1002345678919L, "application_1231111111_1111", null, null));
+    assertEquals(4, types.size());
+
+    types = reader.getEntityTypes(
+        new TimelineReaderContext("cluster1", null, null,
+            null, "application_1231111111_1111", null, null));
+    assertEquals(4, types.size());
+
+    types = reader.getEntityTypes(
+        new TimelineReaderContext("cluster1", null, null,
+            null, "application_1231111111_1112", null, null));
+    assertEquals(4, types.size());
+
+    types = reader.getEntityTypes(
+        new TimelineReaderContext("cluster1", "user1", "some_flow_name",
+            1002345678919L, "application_1231111111_1113", null, null));
+    assertEquals(0, types.size());
+  }
+
   @AfterClass
   public static void tearDownAfterClass() throws Exception {
     util.shutdownMiniCluster();

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/HBaseTimelineReaderImpl.java

@@ -31,6 +31,7 @@
 import org.apache.hadoop.yarn.server.timelineservice.reader.TimelineReaderContext;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.HBaseTimelineStorageUtils;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.TimelineStorageUtils;
+import org.apache.hadoop.yarn.server.timelineservice.storage.reader.EntityTypeReader;
 import org.apache.hadoop.yarn.server.timelineservice.storage.reader.TimelineEntityReader;
 import org.apache.hadoop.yarn.server.timelineservice.storage.reader.TimelineEntityReaderFactory;
 import org.slf4j.Logger;
@@ -86,4 +87,11 @@ public Set<TimelineEntity> getEntities(TimelineReaderContext context,
             filters, dataToRetrieve);
     return reader.readEntities(hbaseConf, conn);
   }
+
+  @Override
+  public Set<String> getEntityTypes(TimelineReaderContext context)
+      throws IOException {
+    EntityTypeReader reader = new EntityTypeReader(context);
+    return reader.readEntityTypes(hbaseConf, conn);
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/common/HBaseTimelineStorageUtils.java

@@ -23,6 +23,7 @@
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.HBaseConfiguration;
+import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.HRegionInfo;
 import org.apache.hadoop.hbase.KeyValue;
 import org.apache.hadoop.hbase.Tag;
@@ -38,6 +39,7 @@
 
 import java.io.IOException;
 import java.text.NumberFormat;
+import java.util.Arrays;
 import java.util.List;
 import java.util.Map;
 
@@ -313,4 +315,38 @@ public static Configuration getTimelineServiceHBaseConf(Configuration conf)
     }
     return hbaseConf;
   }
+
+  /**
+   * Given a row key prefix stored in a byte array, return a byte array for its
+   * immediate next row key.
+   *
+   * @param rowKeyPrefix The provided row key prefix, represented in an array.
+   * @return the closest next row key of the provided row key.
+   */
+  public static byte[] calculateTheClosestNextRowKeyForPrefix(
+      byte[] rowKeyPrefix) {
+    // Essentially we are treating it like an 'unsigned very very long' and
+    // doing +1 manually.
+    // Search for the place where the trailing 0xFFs start
+    int offset = rowKeyPrefix.length;
+    while (offset > 0) {
+      if (rowKeyPrefix[offset - 1] != (byte) 0xFF) {
+        break;
+      }
+      offset--;
+    }
+
+    if (offset == 0) {
+      // We got an 0xFFFF... (only FFs) stopRow value which is
+      // the last possible prefix before the end of the table.
+      // So set it to stop at the 'end of the table'
+      return HConstants.EMPTY_END_ROW;
+    }
+
+    // Copy the right length of the original
+    byte[] newStopRow = Arrays.copyOfRange(rowKeyPrefix, 0, offset);
+    // And increment the last one
+    newStopRow[newStopRow.length - 1]++;
+    return newStopRow;
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/reader/AbstractTimelineStorageReader.java

@@ -0,0 +1,145 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.yarn.server.timelineservice.storage.reader;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.client.Connection;
+import org.apache.hadoop.hbase.client.Get;
+import org.apache.hadoop.hbase.client.Result;
+import org.apache.hadoop.yarn.server.timelineservice.reader.TimelineReaderContext;
+import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowColumn;
+import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowRowKey;
+import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowTable;
+import org.apache.hadoop.yarn.webapp.NotFoundException;
+
+import java.io.IOException;
+
+/**
+ * The base class for reading timeline data from the HBase storage. This class
+ * provides basic support to validate and augment reader context.
+ */
+public abstract class AbstractTimelineStorageReader {
+
+  private final TimelineReaderContext context;
+  /**
+   * Used to look up the flow context.
+   */
+  private final AppToFlowTable appToFlowTable = new AppToFlowTable();
+
+  public AbstractTimelineStorageReader(TimelineReaderContext ctxt) {
+    context = ctxt;
+  }
+
+  protected TimelineReaderContext getContext() {
+    return context;
+  }
+
+  /**
+   * Looks up flow context from AppToFlow table.
+   *
+   * @param appToFlowRowKey to identify Cluster and App Ids.
+   * @param hbaseConf HBase configuration.
+   * @param conn HBase Connection.
+   * @return flow context information.
+   * @throws IOException if any problem occurs while fetching flow information.
+   */
+  protected FlowContext lookupFlowContext(AppToFlowRowKey appToFlowRowKey,
+      Configuration hbaseConf, Connection conn) throws IOException {
+    byte[] rowKey = appToFlowRowKey.getRowKey();
+    Get get = new Get(rowKey);
+    Result result = appToFlowTable.getResult(hbaseConf, conn, get);
+    if (result != null && !result.isEmpty()) {
+      return new FlowContext(AppToFlowColumn.USER_ID.readResult(result)
+          .toString(), AppToFlowColumn.FLOW_ID.readResult(result).toString(),
+          ((Number) AppToFlowColumn.FLOW_RUN_ID.readResult(result))
+          .longValue());
+    } else {
+      throw new NotFoundException(
+          "Unable to find the context flow ID and flow run ID for clusterId="
+              + appToFlowRowKey.getClusterId() + ", appId="
+              + appToFlowRowKey.getAppId());
+    }
+  }
+
+  /**
+    * Sets certain parameters to defaults if the values are not provided.
+    *
+    * @param hbaseConf HBase Configuration.
+    * @param conn HBase Connection.
+    * @throws IOException if any exception is encountered while setting params.
+    */
+  protected void augmentParams(Configuration hbaseConf, Connection conn)
+      throws IOException {
+    defaultAugmentParams(hbaseConf, conn);
+  }
+
+  /**
+   * Default behavior for all timeline readers to augment parameters.
+   *
+   * @param hbaseConf HBase Configuration.
+   * @param conn HBase Connection.
+   * @throws IOException if any exception is encountered while setting params.
+   */
+  final protected void defaultAugmentParams(Configuration hbaseConf,
+      Connection conn) throws IOException {
+    // In reality all three should be null or neither should be null
+    if (context.getFlowName() == null || context.getFlowRunId() == null
+        || context.getUserId() == null) {
+      // Get flow context information from AppToFlow table.
+      AppToFlowRowKey appToFlowRowKey =
+          new AppToFlowRowKey(context.getClusterId(), context.getAppId());
+      FlowContext flowContext =
+          lookupFlowContext(appToFlowRowKey, hbaseConf, conn);
+      context.setFlowName(flowContext.flowName);
+      context.setFlowRunId(flowContext.flowRunId);
+      context.setUserId(flowContext.userId);
+    }
+  }
+
+  /**
+   * Validates the required parameters to read the entities.
+   */
+  protected abstract void validateParams();
+
+  /**
+   * Encapsulates flow context information.
+   */
+  protected static class FlowContext {
+    private final String userId;
+    private final String flowName;
+    private final Long flowRunId;
+
+    public FlowContext(String user, String flowName, Long flowRunId) {
+      this.userId = user;
+      this.flowName = flowName;
+      this.flowRunId = flowRunId;
+    }
+
+    protected String getUserId() {
+      return userId;
+    }
+
+    protected String getFlowName() {
+      return flowName;
+    }
+
+    protected Long getFlowRunId() {
+      return flowRunId;
+    }
+  }
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/reader/ApplicationEntityReader.java

@@ -48,7 +48,6 @@
 import org.apache.hadoop.yarn.server.timelineservice.storage.application.ApplicationRowKey;
 import org.apache.hadoop.yarn.server.timelineservice.storage.application.ApplicationRowKeyPrefix;
 import org.apache.hadoop.yarn.server.timelineservice.storage.application.ApplicationTable;
-import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowRowKey;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.BaseTable;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.RowKeyPrefix;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.TimelineStorageUtils;
@@ -343,20 +342,9 @@ protected void validateParams() {
   @Override
   protected void augmentParams(Configuration hbaseConf, Connection conn)
       throws IOException {
-    TimelineReaderContext context = getContext();
     if (isSingleEntityRead()) {
       // Get flow context information from AppToFlow table.
-      if (context.getFlowName() == null || context.getFlowRunId() == null
+      defaultAugmentParams(hbaseConf, conn);
-          || context.getUserId() == null) {
-        AppToFlowRowKey appToFlowRowKey =
-            new AppToFlowRowKey(context.getClusterId(), context.getAppId());
-        FlowContext flowContext =
-            lookupFlowContext(appToFlowRowKey,
-                hbaseConf, conn);
-        context.setFlowName(flowContext.getFlowName());
-        context.setFlowRunId(flowContext.getFlowRunId());
-        context.setUserId(flowContext.getUserId());
-      }
     }
     // Add configs/metrics to fields to retrieve if confsToRetrieve and/or
     // metricsToRetrieve are specified.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/reader/EntityTypeReader.java

@@ -0,0 +1,181 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.yarn.server.timelineservice.storage.reader;
+
+import com.google.common.base.Preconditions;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.client.Connection;
+import org.apache.hadoop.hbase.client.Result;
+import org.apache.hadoop.hbase.client.ResultScanner;
+import org.apache.hadoop.hbase.client.Scan;
+import org.apache.hadoop.hbase.filter.FilterList;
+import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;
+import org.apache.hadoop.hbase.filter.KeyOnlyFilter;
+import org.apache.hadoop.hbase.filter.PageFilter;
+import org.apache.hadoop.yarn.api.records.timelineservice.TimelineEntity;
+import org.apache.hadoop.yarn.server.timelineservice.reader.TimelineReaderContext;
+import org.apache.hadoop.yarn.server.timelineservice.storage.common.HBaseTimelineStorageUtils;
+import org.apache.hadoop.yarn.server.timelineservice.storage.common.Separator;
+import org.apache.hadoop.yarn.server.timelineservice.storage.common.TimelineStorageUtils;
+import org.apache.hadoop.yarn.server.timelineservice.storage.entity.EntityRowKey;
+import org.apache.hadoop.yarn.server.timelineservice.storage.entity.EntityRowKeyPrefix;
+import org.apache.hadoop.yarn.server.timelineservice.storage.entity.EntityTable;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Set;
+import java.util.TreeSet;
+
+/**
+ * Timeline entity reader for listing all available entity types given one
+ * reader context. Right now only supports listing all entity types within one
+ * YARN application.
+ */
+public final class EntityTypeReader extends AbstractTimelineStorageReader {
+
+  private static final Log LOG = LogFactory.getLog(EntityTypeReader.class);
+  private static final EntityTable ENTITY_TABLE = new EntityTable();
+
+  public EntityTypeReader(TimelineReaderContext context) {
+    super(context);
+  }
+
+  /**
+   * Reads a set of timeline entity types from the HBase storage for the given
+   * context.
+   *
+   * @param hbaseConf HBase Configuration.
+   * @param conn HBase Connection.
+   * @return a set of <cite>TimelineEntity</cite> objects, with only type field
+   *         set.
+   * @throws IOException if any exception is encountered while reading entities.
+   */
+  public Set<String> readEntityTypes(Configuration hbaseConf,
+      Connection conn) throws IOException {
+
+    validateParams();
+    augmentParams(hbaseConf, conn);
+
+    Set<String> types = new TreeSet<>();
+    TimelineReaderContext context = getContext();
+    EntityRowKeyPrefix prefix = new EntityRowKeyPrefix(context.getClusterId(),
+        context.getUserId(), context.getFlowName(), context.getFlowRunId(),
+        context.getAppId());
+    byte[] currRowKey = prefix.getRowKeyPrefix();
+    byte[] nextRowKey = prefix.getRowKeyPrefix();
+    nextRowKey[nextRowKey.length - 1]++;
+
+    FilterList typeFilterList = new FilterList();
+    typeFilterList.addFilter(new FirstKeyOnlyFilter());
+    typeFilterList.addFilter(new KeyOnlyFilter());
+    typeFilterList.addFilter(new PageFilter(1));
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("FilterList created for scan is - " + typeFilterList);
+    }
+
+    int counter = 0;
+    while (true) {
+      try (ResultScanner results
+          = getResult(hbaseConf, conn, typeFilterList, currRowKey, nextRowKey))
+      {
+        TimelineEntity entity = parseEntityForType(results.next());
+        if (entity == null) {
+          break;
+        }
+        ++counter;
+        if (!types.add(entity.getType())) {
+          LOG.warn("Failed to add type " + entity.getType()
+              + " to the result set because there is a duplicated copy. ");
+        }
+        String currType = entity.getType();
+        if (LOG.isDebugEnabled()) {
+          LOG.debug("Current row key: " + Arrays.toString(currRowKey));
+          LOG.debug("New entity type discovered: " + currType);
+        }
+        currRowKey = getNextRowKey(prefix.getRowKeyPrefix(), currType);
+      }
+    }
+    if (LOG.isDebugEnabled()) {
+      LOG.debug("Scanned " + counter + "records for "
+          + types.size() + "types");
+    }
+    return types;
+  }
+
+  @Override
+  protected void validateParams() {
+    Preconditions.checkNotNull(getContext(), "context shouldn't be null");
+    Preconditions.checkNotNull(getContext().getClusterId(),
+        "clusterId shouldn't be null");
+    Preconditions.checkNotNull(getContext().getAppId(),
+        "appId shouldn't be null");
+  }
+
+  /**
+   * Gets the possibly next row key prefix given current prefix and type.
+   *
+   * @param currRowKeyPrefix The current prefix that contains user, cluster,
+   *                         flow, run, and application id.
+   * @param entityType Current entity type.
+   * @return A new prefix for the possibly immediately next row key.
+   */
+  private static byte[] getNextRowKey(byte[] currRowKeyPrefix,
+      String entityType) {
+    if (currRowKeyPrefix == null || entityType == null) {
+      return null;
+    }
+
+    byte[] entityTypeEncoded = Separator.QUALIFIERS.join(
+        Separator.encode(entityType, Separator.SPACE, Separator.TAB,
+            Separator.QUALIFIERS),
+        Separator.EMPTY_BYTES);
+
+    byte[] currRowKey
+        = new byte[currRowKeyPrefix.length + entityTypeEncoded.length];
+    System.arraycopy(currRowKeyPrefix, 0, currRowKey, 0,
+        currRowKeyPrefix.length);
+    System.arraycopy(entityTypeEncoded, 0, currRowKey, currRowKeyPrefix.length,
+        entityTypeEncoded.length);
+
+    return HBaseTimelineStorageUtils.
+        calculateTheClosestNextRowKeyForPrefix(currRowKey);
+  }
+
+  private ResultScanner getResult(Configuration hbaseConf, Connection conn,
+      FilterList filterList, byte[] startPrefix, byte[] endPrefix)
+      throws IOException {
+    Scan scan = new Scan(startPrefix, endPrefix);
+    scan.setFilter(filterList);
+    scan.setSmall(true);
+    return ENTITY_TABLE.getResultScanner(hbaseConf, conn, scan);
+  }
+
+  private TimelineEntity parseEntityForType(Result result)
+      throws IOException {
+    if (result == null || result.isEmpty()) {
+      return null;
+    }
+    TimelineEntity entity = new TimelineEntity();
+    EntityRowKey newRowKey = EntityRowKey.parseRowKey(result.getRow());
+    entity.setType(newRowKey.getEntityType());
+    return entity;
+  }
+
+}

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/reader/GenericEntityReader.java

@@ -41,9 +41,6 @@
 import org.apache.hadoop.yarn.server.timelineservice.reader.filter.TimelineFilterList;
 import org.apache.hadoop.yarn.server.timelineservice.reader.filter.TimelineFilterUtils;
 import org.apache.hadoop.yarn.server.timelineservice.storage.TimelineReader.Field;
-import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowColumn;
-import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowRowKey;
-import org.apache.hadoop.yarn.server.timelineservice.storage.apptoflow.AppToFlowTable;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.BaseTable;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.ColumnPrefix;
 import org.apache.hadoop.yarn.server.timelineservice.storage.common.KeyConverter;
@@ -56,7 +53,6 @@
 import org.apache.hadoop.yarn.server.timelineservice.storage.entity.EntityRowKey;
 import org.apache.hadoop.yarn.server.timelineservice.storage.entity.EntityRowKeyPrefix;
 import org.apache.hadoop.yarn.server.timelineservice.storage.entity.EntityTable;
-import org.apache.hadoop.yarn.webapp.NotFoundException;
 
 import com.google.common.base.Preconditions;
 
@@ -67,11 +63,6 @@
 class GenericEntityReader extends TimelineEntityReader {
   private static final EntityTable ENTITY_TABLE = new EntityTable();
 
-  /**
-   * Used to look up the flow context.
-   */
-  private final AppToFlowTable appToFlowTable = new AppToFlowTable();
-
   /**
    * Used to convert strings key components to and from storage format.
    */
@@ -400,60 +391,6 @@ protected FilterList constructFilterListBasedOnFields() throws IOException {
     return listBasedOnFields;
   }
 
-  /**
-   * Looks up flow context from AppToFlow table.
-   *
-   * @param appToFlowRowKey to identify Cluster and App Ids.
-   * @param hbaseConf HBase configuration.
-   * @param conn HBase Connection.
-   * @return flow context information.
-   * @throws IOException if any problem occurs while fetching flow information.
-   */
-  protected FlowContext lookupFlowContext(AppToFlowRowKey appToFlowRowKey,
-      Configuration hbaseConf, Connection conn) throws IOException {
-    byte[] rowKey = appToFlowRowKey.getRowKey();
-    Get get = new Get(rowKey);
-    Result result = appToFlowTable.getResult(hbaseConf, conn, get);
-    if (result != null && !result.isEmpty()) {
-      return new FlowContext(AppToFlowColumn.USER_ID.readResult(result)
-          .toString(), AppToFlowColumn.FLOW_ID.readResult(result).toString(),
-          ((Number) AppToFlowColumn.FLOW_RUN_ID.readResult(result))
-          .longValue());
-    } else {
-      throw new NotFoundException(
-          "Unable to find the context flow ID and flow run ID for clusterId="
-              + appToFlowRowKey.getClusterId() + ", appId="
-              + appToFlowRowKey.getAppId());
-    }
-  }
-
-  /**
-   * Encapsulates flow context information.
-   */
-  protected static class FlowContext {
-    private final String userId;
-    private final String flowName;
-    private final Long flowRunId;
-
-    public FlowContext(String user, String flowName, Long flowRunId) {
-      this.userId = user;
-      this.flowName = flowName;
-      this.flowRunId = flowRunId;
-    }
-
-    protected String getUserId() {
-      return userId;
-    }
-
-    protected String getFlowName() {
-      return flowName;
-    }
-
-    protected Long getFlowRunId() {
-      return flowRunId;
-    }
-  }
-
   @Override
   protected void validateParams() {
     Preconditions.checkNotNull(getContext(), "context shouldn't be null");
@@ -474,19 +411,7 @@ protected void validateParams() {
   @Override
   protected void augmentParams(Configuration hbaseConf, Connection conn)
       throws IOException {
-    TimelineReaderContext context = getContext();
+    defaultAugmentParams(hbaseConf, conn);
-    // In reality all three should be null or neither should be null
-    if (context.getFlowName() == null || context.getFlowRunId() == null
-        || context.getUserId() == null) {
-      // Get flow context information from AppToFlow table.
-      AppToFlowRowKey appToFlowRowKey =
-          new AppToFlowRowKey(context.getClusterId(), context.getAppId());
-      FlowContext flowContext =
-          lookupFlowContext(appToFlowRowKey, hbaseConf, conn);
-      context.setFlowName(flowContext.flowName);
-      context.setFlowRunId(flowContext.flowRunId);
-      context.setUserId(flowContext.userId);
-    }
     // Add configs/metrics to fields to retrieve if confsToRetrieve and/or
     // metricsToRetrieve are specified.
     getDataToRetrieve().addFieldsBasedOnConfsAndMetricsToRetrieve();

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/reader/TimelineEntityReader.java

@@ -60,12 +60,12 @@
  * HBase storage. Different types can be defined for different types of the
  * entities that are being requested.
  */
-public abstract class TimelineEntityReader {
+public abstract class TimelineEntityReader extends
+    AbstractTimelineStorageReader {
   private static final Logger LOG =
       LoggerFactory.getLogger(TimelineEntityReader.class);
 
   private final boolean singleEntityRead;
-  private TimelineReaderContext context;
   private TimelineDataToRetrieve dataToRetrieve;
   // used only for multiple entity read mode
   private TimelineEntityFilters filters;
@@ -102,9 +102,9 @@ public abstract class TimelineEntityReader {
   protected TimelineEntityReader(TimelineReaderContext ctxt,
       TimelineEntityFilters entityFilters, TimelineDataToRetrieve toRetrieve,
       boolean sortedKeys) {
+    super(ctxt);
     this.singleEntityRead = false;
     this.sortedKeys = sortedKeys;
-    this.context = ctxt;
     this.dataToRetrieve = toRetrieve;
     this.filters = entityFilters;
 
@@ -120,8 +120,8 @@ protected TimelineEntityReader(TimelineReaderContext ctxt,
    */
   protected TimelineEntityReader(TimelineReaderContext ctxt,
       TimelineDataToRetrieve toRetrieve) {
+    super(ctxt);
     this.singleEntityRead = true;
-    this.context = ctxt;
     this.dataToRetrieve = toRetrieve;
 
     this.setTable(getTable());
@@ -185,10 +185,6 @@ private FilterList createFilterList() throws IOException {
     return null;
   }
 
-  protected TimelineReaderContext getContext() {
-    return context;
-  }
-
   protected TimelineDataToRetrieve getDataToRetrieve() {
     return dataToRetrieve;
   }
@@ -229,7 +225,7 @@ public TimelineEntity readEntity(Configuration hbaseConf, Connection conn)
     if (result == null || result.isEmpty()) {
       // Could not find a matching row.
       LOG.info("Cannot find matching entity of type " +
-          context.getEntityType());
+          getContext().getEntityType());
       return null;
     }
     return parseEntity(result);
@@ -288,21 +284,6 @@ protected BaseTable<?> getTable() {
     return table;
   }
 
-  /**
-   * Validates the required parameters to read the entities.
-   */
-  protected abstract void validateParams();
-
-  /**
-   * Sets certain parameters to defaults if the values are not provided.
-   *
-   * @param hbaseConf HBase Configuration.
-   * @param conn HBase Connection.
-   * @throws IOException if any exception is encountered while setting params.
-   */
-  protected abstract void augmentParams(Configuration hbaseConf,
-      Connection conn) throws IOException;
-
   /**
    * Fetches a {@link Result} instance for a single-entity read.
    *

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice-hbase/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/reader/TimelineEntityReaderFactory.java

@@ -86,4 +86,17 @@ public static TimelineEntityReader createMultipleEntitiesReader(
       return new GenericEntityReader(context, filters, dataToRetrieve, false);
     }
   }
+
+  /**
+   * Creates a timeline entity type reader that will read all available entity
+   * types within the specified context.
+   *
+   * @param context Reader context which defines the scope in which query has to
+   *                be made. Limited to application level only.
+   * @return an <cite>EntityTypeReader</cite> object
+   */
+  public static EntityTypeReader createEntityTypeReader(
+      TimelineReaderContext context) {
+    return new EntityTypeReader(context);
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice/src/main/java/org/apache/hadoop/yarn/server/timelineservice/reader/TimelineReaderManager.java

@@ -176,4 +176,24 @@ public TimelineEntity getEntity(TimelineReaderContext context,
     }
     return entity;
   }
+
+  /**
+   * Gets a list of available timeline entity types for an application. This can
+   * be done by making a call to the backend storage implementation. The meaning
+   * of each argument in detail is the same as {@link TimelineReader#getEntity}.
+   * If cluster ID has not been supplied by the client, fills the cluster id
+   * from config before making a call to backend storage.
+   *
+   * @param context Timeline context within the scope of which entity types
+   *                have to be fetched. Entity type field of this context should
+   *                be null.
+   * @return A set which contains available timeline entity types, represented
+   * as strings if found, empty otherwise.
+   * @throws IOException  if any problem occurs while getting entity types.
+   */
+  public Set<String> getEntityTypes(TimelineReaderContext context)
+      throws IOException{
+    context.setClusterId(getClusterID(context.getClusterId(), getConfig()));
+    return reader.getEntityTypes(new TimelineReaderContext(context));
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice/src/main/java/org/apache/hadoop/yarn/server/timelineservice/reader/TimelineReaderWebServices.java

@@ -2860,4 +2860,106 @@ public TimelineEntity getContainer(@Context HttpServletRequest req,
         flowName, flowRunId, confsToRetrieve, metricsToRetrieve, fields,
         metricsLimit);
   }
+
+  /**
+   * Returns a set of available entity types for a given app id. Cluster ID is
+   * not provided by client so default cluster ID has to be taken. If userid,
+   * flow name and flow run id which are optional query parameters are not
+   * specified, they will be queried based on app id and cluster id from the
+   * flow context information stored in underlying storage implementation.
+   *
+   * @param req Servlet request.
+   * @param res Servlet response.
+   * @param appId Application id to be queried(Mandatory path param).
+   * @param flowName Flow name which should match for the app(Optional query
+   *     param).
+   * @param flowRunId Run id which should match for the app(Optional query
+   *     param).
+   * @param userId User id which should match for the app(Optional query param).
+   *
+   * @return If successful, a HTTP 200(OK) response having a JSON representing a
+   *     list contains all timeline entity types is returned.<br>
+   *     On failures,<br>
+   *     If any problem occurs in parsing request, HTTP 400(Bad Request) is
+   *     returned.<br>
+   *     If flow context information cannot be retrieved or app for the given
+   *     app id cannot be found, HTTP 404(Not Found) is returned.<br>
+   *     For all other errors while retrieving data, HTTP 500(Internal Server
+   *     Error) is returned.
+   */
+  @GET
+  @Path("/apps/{appid}/entity-types")
+  @Produces(MediaType.APPLICATION_JSON)
+  public Set<String> getEntityTypes(
+      @Context HttpServletRequest req,
+      @Context HttpServletResponse res,
+      @PathParam("appid") String appId,
+      @QueryParam("flowname") String flowName,
+      @QueryParam("flowrunid") String flowRunId,
+      @QueryParam("userid") String userId) {
+    return getEntityTypes(req, res, null, appId, flowName, flowRunId, userId);
+  }
+
+  /**
+   * Returns a set of available entity types for a given app id. If userid,
+   * flow name and flow run id which are optional query parameters are not
+   * specified, they will be queried based on app id and cluster id from the
+   * flow context information stored in underlying storage implementation.
+   *
+   * @param req Servlet request.
+   * @param res Servlet response.
+   * @param clusterId Cluster id to which the app to be queried belong to(
+   *     Mandatory path param).
+   * @param appId Application id to be queried(Mandatory path param).
+   * @param flowName Flow name which should match for the app(Optional query
+   *     param).
+   * @param flowRunId Run id which should match for the app(Optional query
+   *     param).
+   * @param userId User id which should match for the app(Optional query param).
+   *
+   * @return If successful, a HTTP 200(OK) response having a JSON representing a
+   *     list contains all timeline entity types is returned.<br>
+   *     On failures,<br>
+   *     If any problem occurs in parsing request, HTTP 400(Bad Request) is
+   *     returned.<br>
+   *     If flow context information cannot be retrieved or app for the given
+   *     app id cannot be found, HTTP 404(Not Found) is returned.<br>
+   *     For all other errors while retrieving data, HTTP 500(Internal Server
+   *     Error) is returned.
+   */
+  @GET
+  @Path("/clusters/{clusterid}/apps/{appid}/entity-types")
+  @Produces(MediaType.APPLICATION_JSON)
+  public Set<String> getEntityTypes(
+      @Context HttpServletRequest req,
+      @Context HttpServletResponse res,
+      @PathParam("clusterid") String clusterId,
+      @PathParam("appid") String appId,
+      @QueryParam("flowname") String flowName,
+      @QueryParam("flowrunid") String flowRunId,
+      @QueryParam("userid") String userId) {
+    String url = req.getRequestURI() +
+        (req.getQueryString() == null ? "" :
+            QUERY_STRING_SEP + req.getQueryString());
+    UserGroupInformation callerUGI =
+        TimelineReaderWebServicesUtils.getUser(req);
+    LOG.info("Received URL " + url + " from user " +
+        TimelineReaderWebServicesUtils.getUserName(callerUGI));
+    long startTime = Time.monotonicNow();
+    init(res);
+    TimelineReaderManager timelineReaderManager = getTimelineReaderManager();
+    Set<String> results = null;
+    try {
+      results = timelineReaderManager.getEntityTypes(
+          TimelineReaderWebServicesUtils.createTimelineReaderContext(
+          clusterId, userId, flowName, flowRunId, appId,
+          null, null));
+    } catch (Exception e) {
+      handleException(e, url, startTime, "flowrunid");
+    }
+    long endTime = Time.monotonicNow();
+    LOG.info("Processed URL " + url +
+        " (Took " + (endTime - startTime) + " ms.)");
+    return results;
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/FileSystemTimelineReaderImpl.java

@@ -32,6 +32,7 @@
 import java.util.Map.Entry;
 import java.util.Set;
 import java.util.TreeMap;
+import java.util.TreeSet;
 
 import com.fasterxml.jackson.core.JsonGenerationException;
 import com.fasterxml.jackson.databind.JsonMappingException;
@@ -408,4 +409,24 @@ public Set<TimelineEntity> getEntities(TimelineReaderContext context,
             context.getEntityType());
     return getEntities(dir, context.getEntityType(), filters, dataToRetrieve);
   }
+
+  @Override public Set<String> getEntityTypes(TimelineReaderContext context)
+      throws IOException {
+    Set<String> result = new TreeSet<>();
+    String flowRunPath = getFlowRunPath(context.getUserId(),
+        context.getClusterId(), context.getFlowName(), context.getFlowRunId(),
+        context.getAppId());
+    File dir = new File(new File(rootPath, ENTITIES_DIR),
+        context.getClusterId() + File.separator + flowRunPath
+            + File.separator + context.getAppId());
+    File[] fileList = dir.listFiles();
+    if (fileList != null) {
+      for (File f : fileList) {
+        if (f.isDirectory()) {
+          result.add(f.getName());
+        }
+      }
+    }
+    return result;
+  }
 }

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/TimelineReader.java

@@ -177,4 +177,17 @@ Set<TimelineEntity> getEntities(
       TimelineReaderContext context,
       TimelineEntityFilters filters,
       TimelineDataToRetrieve dataToRetrieve) throws IOException;
+
+  /**
+   * The API to list all available entity types of the given context.
+   *
+   * @param context A context defines the scope of this query. The incoming
+   * context should contain at least the cluster id and application id.
+   *
+   * @return A set of entity types available in the given context.
+   *
+   * @throws IOException if an exception occurred while listing from backend
+   * storage.
+   */
+  Set<String> getEntityTypes(TimelineReaderContext context) throws IOException;
 }