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YARN-3878. AsyncDispatcher can hang while stopping if it is configured for draining events on stop. Contributed by Varun Saxena
(cherry picked from commit 393fe71771e3ac6bc0efe59d9aaf19d3576411b3)

Jian He vor 10 Jahren
Ursprung
Commit
11cb00f7a0

+ 3 - 0
hadoop-yarn-project/CHANGES.txt

@@ -630,6 +630,9 @@ Release 2.7.2 - UNRELEASED
     YARN-3535. Scheduler must re-request container resources when RMContainer transitions
     from ALLOCATED to KILLED (rohithsharma and peng.zhang via asuresh)
 
+    YARN-3878. AsyncDispatcher can hang while stopping if it is configured for
+    draining events on stop. (Varun Saxena via jianhe)
+
 Release 2.7.1 - 2015-07-06 
 
   INCOMPATIBLE CHANGES

+ 8 - 0
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/event/AsyncDispatcher.java

@@ -246,6 +246,9 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
         if (!stopped) {
           LOG.warn("AsyncDispatcher thread interrupted", e);
         }
+        // Need to reset drained flag to true if event queue is empty,
+        // otherwise dispatcher will hang on stop.
+        drained = eventQueue.isEmpty();
         throw new YarnRuntimeException(e);
       }
     };
@@ -286,6 +289,11 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
     };
   }
 
+  @VisibleForTesting
+  protected boolean isEventThreadWaiting() {
+    return eventHandlingThread.getState() == Thread.State.WAITING;
+  }
+
   @VisibleForTesting
   protected boolean isDrained() {
     return this.drained;

+ 10 - 1
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/event/DrainDispatcher.java

@@ -27,10 +27,19 @@ public class DrainDispatcher extends AsyncDispatcher {
     this(new LinkedBlockingQueue<Event>());
   }
 
-  private DrainDispatcher(BlockingQueue<Event> eventQueue) {
+  public DrainDispatcher(BlockingQueue<Event> eventQueue) {
     super(eventQueue);
   }
 
+  /**
+   *  Wait till event thread enters WAITING state (i.e. waiting for new events).
+   */
+  public void waitForEventThreadToWait() {
+    while (!isEventThreadWaiting()) {
+      Thread.yield();
+    }
+  }
+
   /**
    * Busy loop waiting for all queued events to drain.
    */

+ 62 - 0
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/event/TestAsyncDispatcher.java

@@ -0,0 +1,62 @@
+/**
+ * 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.event;
+
+import static org.mockito.Mockito.doThrow;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.spy;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.LinkedBlockingQueue;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.yarn.exceptions.YarnRuntimeException;
+import org.junit.Assert;
+import org.junit.Test;
+
+public class TestAsyncDispatcher {
+
+  /* This test checks whether dispatcher hangs on close if following two things
+   * happen :
+   * 1. A thread which was putting event to event queue is interrupted.
+   * 2. Event queue is empty on close.
+   */
+  @SuppressWarnings({ "unchecked", "rawtypes" })
+  @Test(timeout=10000)
+  public void testDispatcherOnCloseIfQueueEmpty() throws Exception {
+    BlockingQueue<Event> eventQueue = spy(new LinkedBlockingQueue<Event>());
+    Event event = mock(Event.class);
+    doThrow(new InterruptedException()).when(eventQueue).put(event);
+    DrainDispatcher disp = new DrainDispatcher(eventQueue);
+    disp.init(new Configuration());
+    disp.setDrainEventsOnStop();
+    disp.start();
+    // Wait for event handler thread to start and begin waiting for events.
+    disp.waitForEventThreadToWait();
+    try {
+      disp.getEventHandler().handle(event);
+    } catch (YarnRuntimeException e) {
+    }
+    // Queue should be empty and dispatcher should not hang on close
+    Assert.assertTrue("Event Queue should have been empty",
+        eventQueue.isEmpty());
+    disp.close();
+  }
+}
+