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/**
* 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.mapreduce.task.reduce;
import java.io.IOException;
import java.util.Map;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapOutputFile;
import org.apache.hadoop.mapred.RawKeyValueIterator;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.Task;
import org.apache.hadoop.mapred.TaskStatus;
import org.apache.hadoop.mapred.TaskUmbilicalProtocol;
import org.apache.hadoop.mapred.ShuffleConsumerPlugin;
import org.apache.hadoop.mapreduce.MRJobConfig;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.util.Progress;
@InterfaceAudience.LimitedPrivate({"MapReduce"})
@InterfaceStability.Unstable
@SuppressWarnings({"unchecked", "rawtypes"})
public class Shuffle implements ShuffleConsumerPlugin,
ExceptionReporter {
private static final int PROGRESS_FREQUENCY = 2000;
private static final int MAX_EVENTS_TO_FETCH = 10000;
private static final int MIN_EVENTS_TO_FETCH = 100;
private static final int MAX_RPC_OUTSTANDING_EVENTS = 3000000;
private ShuffleConsumerPlugin.Context context;
private TaskAttemptID reduceId;
private JobConf jobConf;
private Reporter reporter;
private ShuffleClientMetrics metrics;
private TaskUmbilicalProtocol umbilical;
private ShuffleSchedulerImpl scheduler;
private MergeManager merger;
private Throwable throwable = null;
private String throwingThreadName = null;
private Progress copyPhase;
private TaskStatus taskStatus;
private Task reduceTask; //Used for status updates
private Map localMapFiles;
@Override
public void init(ShuffleConsumerPlugin.Context context) {
this.context = context;
this.reduceId = context.getReduceId();
this.jobConf = context.getJobConf();
this.umbilical = context.getUmbilical();
this.reporter = context.getReporter();
this.metrics = ShuffleClientMetrics.create(context.getReduceId(),
this.jobConf);
this.copyPhase = context.getCopyPhase();
this.taskStatus = context.getStatus();
this.reduceTask = context.getReduceTask();
this.localMapFiles = context.getLocalMapFiles();
scheduler = new ShuffleSchedulerImpl(jobConf, taskStatus, reduceId,
this, copyPhase, context.getShuffledMapsCounter(),
context.getReduceShuffleBytes(), context.getFailedShuffleCounter());
merger = createMergeManager(context);
}
protected MergeManager createMergeManager(
ShuffleConsumerPlugin.Context context) {
return new MergeManagerImpl(reduceId, jobConf, context.getLocalFS(),
context.getLocalDirAllocator(), reporter, context.getCodec(),
context.getCombinerClass(), context.getCombineCollector(),
context.getSpilledRecordsCounter(),
context.getReduceCombineInputCounter(),
context.getMergedMapOutputsCounter(), this, context.getMergePhase(),
context.getMapOutputFile());
}
@Override
public RawKeyValueIterator run() throws IOException, InterruptedException {
// Scale the maximum events we fetch per RPC call to mitigate OOM issues
// on the ApplicationMaster when a thundering herd of reducers fetch events
// TODO: This should not be necessary after HADOOP-8942
int eventsPerReducer = Math.max(MIN_EVENTS_TO_FETCH,
MAX_RPC_OUTSTANDING_EVENTS / jobConf.getNumReduceTasks());
int maxEventsToFetch = Math.min(MAX_EVENTS_TO_FETCH, eventsPerReducer);
// Start the map-completion events fetcher thread
final EventFetcher eventFetcher =
new EventFetcher(reduceId, umbilical, scheduler, this,
maxEventsToFetch);
eventFetcher.start();
// Start the map-output fetcher threads
boolean isLocal = localMapFiles != null;
final int numFetchers = isLocal ? 1 :
jobConf.getInt(MRJobConfig.SHUFFLE_PARALLEL_COPIES, 5);
Fetcher[] fetchers = new Fetcher[numFetchers];
if (isLocal) {
fetchers[0] = new LocalFetcher(jobConf, reduceId, scheduler,
merger, reporter, metrics, this, reduceTask.getShuffleSecret(),
localMapFiles);
fetchers[0].start();
} else {
for (int i=0; i < numFetchers; ++i) {
fetchers[i] = new Fetcher(jobConf, reduceId, scheduler, merger,
reporter, metrics, this,
reduceTask.getShuffleSecret());
fetchers[i].start();
}
}
// Wait for shuffle to complete successfully
while (!scheduler.waitUntilDone(PROGRESS_FREQUENCY)) {
reporter.progress();
synchronized (this) {
if (throwable != null) {
throw new ShuffleError("error in shuffle in " + throwingThreadName,
throwable);
}
}
}
// Stop the event-fetcher thread
eventFetcher.shutDown();
// Stop the map-output fetcher threads
for (Fetcher fetcher : fetchers) {
fetcher.shutDown();
}
// stop the scheduler
scheduler.close();
copyPhase.complete(); // copy is already complete
taskStatus.setPhase(TaskStatus.Phase.SORT);
reduceTask.statusUpdate(umbilical);
// Finish the on-going merges...
RawKeyValueIterator kvIter = null;
try {
kvIter = merger.close();
} catch (Throwable e) {
throw new ShuffleError("Error while doing final merge ", e);
}
// Sanity check
synchronized (this) {
if (throwable != null) {
throw new ShuffleError("error in shuffle in " + throwingThreadName,
throwable);
}
}
return kvIter;
}
@Override
public void close(){
}
public synchronized void reportException(Throwable t) {
if (throwable == null) {
throwable = t;
throwingThreadName = Thread.currentThread().getName();
// Notify the scheduler so that the reporting thread finds the
// exception immediately.
synchronized (scheduler) {
scheduler.notifyAll();
}
}
}
public static class ShuffleError extends IOException {
private static final long serialVersionUID = 5753909320586607881L;
ShuffleError(String msg, Throwable t) {
super(msg, t);
}
}
}