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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.hbase.mapreduce;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.mapreduce.Counter;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.MapContext;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.StatusReporter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.util.ReflectionUtils;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Multithreaded implementation for @link org.apache.hbase.mapreduce.TableMapper
*
* It can be used instead when the Map operation is not CPU bound in order to improve throughput.
*
* Mapper implementations using this MapRunnable must be thread-safe.
*
* The Map-Reduce job has to be configured with the mapper to use via {@link #setMapperClass} and
* the number of thread the thread-pool can use with the {@link #getNumberOfThreads} method. The
* default value is 10 threads.
*
*/
@InterfaceAudience.Private
public class MultithreadedTableMapper extends TableMapper {
private static final Logger LOG = LoggerFactory.getLogger(MultithreadedTableMapper.class);
private Class> mapClass;
private Context outer;
private ExecutorService executor;
public static final String NUMBER_OF_THREADS = "hbase.mapreduce.multithreadedmapper.threads";
public static final String MAPPER_CLASS = "hbase.mapreduce.multithreadedmapper.mapclass";
/**
* The number of threads in the thread pool that will run the map function.
* @param job the job
* @return the number of threads
*/
public static int getNumberOfThreads(JobContext job) {
return job.getConfiguration().getInt(NUMBER_OF_THREADS, 10);
}
/**
* Set the number of threads in the pool for running maps.
* @param job the job to modify
* @param threads the new number of threads
*/
public static void setNumberOfThreads(Job job, int threads) {
job.getConfiguration().setInt(NUMBER_OF_THREADS, threads);
}
/**
* Get the application's mapper class.
* @param the map's output key type
* @param the map's output value type
* @param job the job
* @return the mapper class to run
*/
@SuppressWarnings("unchecked")
public static Class>
getMapperClass(JobContext job) {
return (Class>) job.getConfiguration()
.getClass(MAPPER_CLASS, Mapper.class);
}
/**
* Set the application's mapper class.
* @param the map output key type
* @param the map output value type
* @param job the job to modify
* @param cls the class to use as the mapper
*/
public static void setMapperClass(Job job,
Class> cls) {
if (MultithreadedTableMapper.class.isAssignableFrom(cls)) {
throw new IllegalArgumentException(
"Can't have recursive " + "MultithreadedTableMapper instances.");
}
job.getConfiguration().setClass(MAPPER_CLASS, cls, Mapper.class);
}
/**
* Run the application's maps using a thread pool.
*/
@Override
public void run(Context context) throws IOException, InterruptedException {
outer = context;
int numberOfThreads = getNumberOfThreads(context);
mapClass = getMapperClass(context);
if (LOG.isDebugEnabled()) {
LOG.debug("Configuring multithread runner to use " + numberOfThreads + " threads");
}
executor = Executors.newFixedThreadPool(numberOfThreads);
for (int i = 0; i < numberOfThreads; ++i) {
MapRunner thread = new MapRunner(context);
executor.execute(thread);
}
executor.shutdown();
while (!executor.isTerminated()) {
// wait till all the threads are done
Thread.sleep(1000);
}
}
private class SubMapRecordReader extends RecordReader {
private ImmutableBytesWritable key;
private Result value;
private Configuration conf;
@Override
public void close() throws IOException {
}
@Override
public float getProgress() throws IOException, InterruptedException {
return 0;
}
@Override
public void initialize(InputSplit split, TaskAttemptContext context)
throws IOException, InterruptedException {
conf = context.getConfiguration();
}
@Override
public boolean nextKeyValue() throws IOException, InterruptedException {
synchronized (outer) {
if (!outer.nextKeyValue()) {
return false;
}
key = ReflectionUtils.copy(outer.getConfiguration(), outer.getCurrentKey(), key);
value = ReflectionUtils.copy(conf, outer.getCurrentValue(), value);
return true;
}
}
public ImmutableBytesWritable getCurrentKey() {
return key;
}
@Override
public Result getCurrentValue() {
return value;
}
}
private class SubMapRecordWriter extends RecordWriter {
@Override
public void close(TaskAttemptContext context) throws IOException, InterruptedException {
}
@Override
public void write(K2 key, V2 value) throws IOException, InterruptedException {
synchronized (outer) {
outer.write(key, value);
}
}
}
private class SubMapStatusReporter extends StatusReporter {
@Override
public Counter getCounter(Enum name) {
return outer.getCounter(name);
}
@Override
public Counter getCounter(String group, String name) {
return outer.getCounter(group, name);
}
@Override
public void progress() {
outer.progress();
}
@Override
public void setStatus(String status) {
outer.setStatus(status);
}
public float getProgress() {
return 0;
}
}
@edu.umd.cs.findbugs.annotations.SuppressWarnings(value = "REC_CATCH_EXCEPTION",
justification = "Don't understand why FB is complaining about this one."
+ " We do throw exception")
private class MapRunner implements Runnable {
private Mapper mapper;
private Context subcontext;
@SuppressWarnings({ "rawtypes", "unchecked" })
MapRunner(Context context) throws IOException, InterruptedException {
mapper = ReflectionUtils.newInstance(mapClass, context.getConfiguration());
try {
Constructor c = context.getClass().getConstructor(Mapper.class, Configuration.class,
TaskAttemptID.class, RecordReader.class, RecordWriter.class, OutputCommitter.class,
StatusReporter.class, InputSplit.class);
c.setAccessible(true);
subcontext = (Context) c.newInstance(mapper, outer.getConfiguration(),
outer.getTaskAttemptID(), new SubMapRecordReader(), new SubMapRecordWriter(),
context.getOutputCommitter(), new SubMapStatusReporter(), outer.getInputSplit());
} catch (Exception e) {
try {
Constructor c = Class.forName("org.apache.hadoop.mapreduce.task.MapContextImpl")
.getConstructor(Configuration.class, TaskAttemptID.class, RecordReader.class,
RecordWriter.class, OutputCommitter.class, StatusReporter.class, InputSplit.class);
c.setAccessible(true);
MapContext mc = (MapContext) c.newInstance(outer.getConfiguration(),
outer.getTaskAttemptID(), new SubMapRecordReader(), new SubMapRecordWriter(),
context.getOutputCommitter(), new SubMapStatusReporter(), outer.getInputSplit());
Class wrappedMapperClass =
Class.forName("org.apache.hadoop.mapreduce.lib.map.WrappedMapper");
Method getMapContext = wrappedMapperClass.getMethod("getMapContext", MapContext.class);
subcontext = (Context) getMapContext
.invoke(wrappedMapperClass.getDeclaredConstructor().newInstance(), mc);
} catch (Exception ee) { // FindBugs: REC_CATCH_EXCEPTION
// rethrow as IOE
throw new IOException(e);
}
}
}
@Override
public void run() {
try {
mapper.run(subcontext);
} catch (Throwable ie) {
LOG.error("Problem in running map.", ie);
}
}
}
}