YARN-3878. AsyncDispatcher can hang while stopping if it is configured for draining events on stop. (Varun Saxena via kasha)
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@ -624,6 +624,9 @@ Release 2.7.2 - UNRELEASED
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YARN-3690. [JDK8] 'mvn site' fails. (Brahma Reddy Battula via aajisaka)
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YARN-3878. AsyncDispatcher can hang while stopping if it is configured for
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draining events on stop. (Varun Saxena via kasha)
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Release 2.7.1 - 2015-07-06
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INCOMPATIBLE CHANGES
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@ -55,9 +55,6 @@ public class AsyncDispatcher extends AbstractService implements Dispatcher {
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// stop functionality.
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private volatile boolean drainEventsOnStop = false;
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// Indicates all the remaining dispatcher's events on stop have been drained
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// and processed.
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private volatile boolean drained = true;
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private Object waitForDrained = new Object();
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// For drainEventsOnStop enabled only, block newly coming events into the
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@ -84,13 +81,12 @@ Runnable createThread() {
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@Override
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public void run() {
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while (!stopped && !Thread.currentThread().isInterrupted()) {
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drained = eventQueue.isEmpty();
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// blockNewEvents is only set when dispatcher is draining to stop,
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// adding this check is to avoid the overhead of acquiring the lock
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// and calling notify every time in the normal run of the loop.
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if (blockNewEvents) {
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synchronized (waitForDrained) {
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if (drained) {
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if (eventQueue.isEmpty()) {
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waitForDrained.notify();
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}
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}
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@ -139,7 +135,7 @@ protected void serviceStop() throws Exception {
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blockNewEvents = true;
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LOG.info("AsyncDispatcher is draining to stop, igonring any new events.");
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synchronized (waitForDrained) {
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while (!drained && eventHandlingThread.isAlive()) {
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while (!eventQueue.isEmpty() && eventHandlingThread.isAlive()) {
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waitForDrained.wait(1000);
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LOG.info("Waiting for AsyncDispatcher to drain. Thread state is :" +
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eventHandlingThread.getState());
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@ -223,12 +219,21 @@ public EventHandler getEventHandler() {
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return handlerInstance;
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}
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@VisibleForTesting
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protected boolean hasPendingEvents() {
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return !eventQueue.isEmpty();
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}
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@VisibleForTesting
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protected boolean isEventThreadWaiting() {
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return eventHandlingThread.getState() == Thread.State.WAITING;
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}
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class GenericEventHandler implements EventHandler<Event> {
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public void handle(Event event) {
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if (blockNewEvents) {
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return;
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}
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drained = false;
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/* all this method does is enqueue all the events onto the queue */
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int qSize = eventQueue.size();
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@ -285,9 +290,4 @@ public void run() {
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}
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};
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}
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@VisibleForTesting
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protected boolean isDrained() {
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return this.drained;
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}
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}
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@ -27,15 +27,24 @@ public DrainDispatcher() {
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this(new LinkedBlockingQueue<Event>());
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}
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private DrainDispatcher(BlockingQueue<Event> eventQueue) {
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public DrainDispatcher(BlockingQueue<Event> eventQueue) {
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super(eventQueue);
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}
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/**
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* Wait till event thread enters WAITING state (i.e. waiting for new events).
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*/
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public void waitForEventThreadToWait() {
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while (!isEventThreadWaiting()) {
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Thread.yield();
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}
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}
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/**
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* Busy loop waiting for all queued events to drain.
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*/
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public void await() {
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while (!isDrained()) {
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while (hasPendingEvents()) {
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Thread.yield();
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}
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}
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@ -0,0 +1,61 @@
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/**
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.hadoop.yarn.event;
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import static org.mockito.Mockito.doThrow;
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import static org.mockito.Mockito.mock;
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import static org.mockito.Mockito.spy;
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import java.util.concurrent.BlockingQueue;
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import java.util.concurrent.LinkedBlockingQueue;
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import org.apache.hadoop.conf.Configuration;
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import org.apache.hadoop.yarn.exceptions.YarnRuntimeException;
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import org.junit.Assert;
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import org.junit.Test;
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public class TestAsyncDispatcher {
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/* This test checks whether dispatcher hangs on close if following two things
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* happen :
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* 1. A thread which was putting event to event queue is interrupted.
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* 2. Event queue is empty on close.
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*/
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@SuppressWarnings({ "unchecked", "rawtypes" })
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@Test(timeout=10000)
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public void testDispatcherOnCloseIfQueueEmpty() throws Exception {
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BlockingQueue<Event> eventQueue = spy(new LinkedBlockingQueue<Event>());
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Event event = mock(Event.class);
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doThrow(new InterruptedException()).when(eventQueue).put(event);
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DrainDispatcher disp = new DrainDispatcher(eventQueue);
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disp.init(new Configuration());
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disp.setDrainEventsOnStop();
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disp.start();
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// Wait for event handler thread to start and begin waiting for events.
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disp.waitForEventThreadToWait();
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try {
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disp.getEventHandler().handle(event);
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} catch (YarnRuntimeException e) {
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}
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// Queue should be empty and dispatcher should not hang on close
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Assert.assertTrue("Event Queue should have been empty",
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eventQueue.isEmpty());
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disp.close();
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}
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}
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