/**
* 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.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.ChecksumFileSystem;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.LocalDirAllocator;
import org.apache.hadoop.fs.LocalFileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.RawComparator;
import org.apache.hadoop.io.compress.CompressionCodec;
import org.apache.hadoop.mapred.Counters;
import org.apache.hadoop.mapred.IFile;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapOutputFile;
import org.apache.hadoop.mapred.Merger;
import org.apache.hadoop.mapred.RawKeyValueIterator;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.Task;
import org.apache.hadoop.mapred.IFile.Reader;
import org.apache.hadoop.mapred.IFile.Writer;
import org.apache.hadoop.mapred.Merger.Segment;
import org.apache.hadoop.mapred.Task.CombineOutputCollector;
import org.apache.hadoop.mapred.Task.CombineValuesIterator;
import org.apache.hadoop.mapreduce.MRJobConfig;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.TaskID;
import org.apache.hadoop.mapreduce.task.reduce.MapOutput.MapOutputComparator;
import org.apache.hadoop.util.Progress;
import org.apache.hadoop.util.ReflectionUtils;
import com.google.common.annotations.VisibleForTesting;
@SuppressWarnings(value={"unchecked"})
@InterfaceAudience.LimitedPrivate({"MapReduce"})
@InterfaceStability.Unstable
public class MergeManagerImpl<K, V> implements MergeManager<K, V> {
private static final Log LOG = LogFactory.getLog(MergeManagerImpl.class);
/* Maximum percentage of the in-memory limit that a single shuffle can
* consume*/
private static final float DEFAULT_SHUFFLE_MEMORY_LIMIT_PERCENT
= 0.25f;
private final TaskAttemptID reduceId;
private final JobConf jobConf;
private final FileSystem localFS;
private final FileSystem rfs;
private final LocalDirAllocator localDirAllocator;
protected MapOutputFile mapOutputFile;
Set<InMemoryMapOutput<K, V>> inMemoryMergedMapOutputs =
new TreeSet<InMemoryMapOutput<K,V>>(new MapOutputComparator<K, V>());
private IntermediateMemoryToMemoryMerger memToMemMerger;
Set<InMemoryMapOutput<K, V>> inMemoryMapOutputs =
new TreeSet<InMemoryMapOutput<K,V>>(new MapOutputComparator<K, V>());
private final MergeThread<InMemoryMapOutput<K,V>, K,V> inMemoryMerger;
Set<CompressAwarePath> onDiskMapOutputs = new TreeSet<CompressAwarePath>();
private final OnDiskMerger onDiskMerger;
private final long memoryLimit;
private long usedMemory;
private long commitMemory;
private final long maxSingleShuffleLimit;
private final int memToMemMergeOutputsThreshold;
private final long mergeThreshold;
private final int ioSortFactor;
private final Reporter reporter;
private final ExceptionReporter exceptionReporter;
/**
* Combiner class to run during in-memory merge, if defined.
*/
private final Class<? extends Reducer> combinerClass;
/**
* Resettable collector used for combine.
*/
private final CombineOutputCollector<K,V> combineCollector;
private final Counters.Counter spilledRecordsCounter;
private final Counters.Counter reduceCombineInputCounter;
private final Counters.Counter mergedMapOutputsCounter;
private final CompressionCodec codec;
private final Progress mergePhase;
public MergeManagerImpl(TaskAttemptID reduceId, JobConf jobConf,
FileSystem localFS,
LocalDirAllocator localDirAllocator,
Reporter reporter,
CompressionCodec codec,
Class<? extends Reducer> combinerClass,
CombineOutputCollector<K,V> combineCollector,
Counters.Counter spilledRecordsCounter,
Counters.Counter reduceCombineInputCounter,
Counters.Counter mergedMapOutputsCounter,
ExceptionReporter exceptionReporter,
Progress mergePhase, MapOutputFile mapOutputFile) {
this.reduceId = reduceId;
this.jobConf = jobConf;
this.localDirAllocator = localDirAllocator;
this.exceptionReporter = exceptionReporter;
this.reporter = reporter;
this.codec = codec;
this.combinerClass = combinerClass;
this.combineCollector = combineCollector;
this.reduceCombineInputCounter = reduceCombineInputCounter;
this.spilledRecordsCounter = spilledRecordsCounter;
this.mergedMapOutputsCounter = mergedMapOutputsCounter;
this.mapOutputFile = mapOutputFile;
this.mapOutputFile.setConf(jobConf);
this.localFS = localFS;
this.rfs = ((LocalFileSystem)localFS).getRaw();
final float maxInMemCopyUse =
jobConf.getFloat(MRJobConfig.SHUFFLE_INPUT_BUFFER_PERCENT, 0.90f);
if (maxInMemCopyUse > 1.0 || maxInMemCopyUse < 0.0) {
throw new IllegalArgumentException("Invalid value for " +
MRJobConfig.SHUFFLE_INPUT_BUFFER_PERCENT + ": " +
maxInMemCopyUse);
}
// Allow unit tests to fix Runtime memory
this.memoryLimit =
(long)(jobConf.getLong(MRJobConfig.REDUCE_MEMORY_TOTAL_BYTES,
Math.min(Runtime.getRuntime().maxMemory(), Integer.MAX_VALUE))
* maxInMemCopyUse);
this.ioSortFactor = jobConf.getInt(MRJobConfig.IO_SORT_FACTOR, 100);
final float singleShuffleMemoryLimitPercent =
jobConf.getFloat(MRJobConfig.SHUFFLE_MEMORY_LIMIT_PERCENT,
DEFAULT_SHUFFLE_MEMORY_LIMIT_PERCENT);
if (singleShuffleMemoryLimitPercent <= 0.0f
|| singleShuffleMemoryLimitPercent > 1.0f) {
throw new IllegalArgumentException("Invalid value for "
+ MRJobConfig.SHUFFLE_MEMORY_LIMIT_PERCENT + ": "
+ singleShuffleMemoryLimitPercent);
}
usedMemory = 0L;
commitMemory = 0L;
this.maxSingleShuffleLimit =
(long)(memoryLimit * singleShuffleMemoryLimitPercent);
this.memToMemMergeOutputsThreshold =
jobConf.getInt(MRJobConfig.REDUCE_MEMTOMEM_THRESHOLD, ioSortFactor);
this.mergeThreshold = (long)(this.memoryLimit *
jobConf.getFloat(MRJobConfig.SHUFFLE_MERGE_PERCENT,
0.90f));
LOG.info("MergerManager: memoryLimit=" + memoryLimit + ", " +
"maxSingleShuffleLimit=" + maxSingleShuffleLimit + ", " +
"mergeThreshold=" + mergeThreshold + ", " +
"ioSortFactor=" + ioSortFactor + ", " +
"memToMemMergeOutputsThreshold=" + memToMemMergeOutputsThreshold);
if (this.maxSingleShuffleLimit >= this.mergeThreshold) {
throw new RuntimeException("Invlaid configuration: "
+ "maxSingleShuffleLimit should be less than mergeThreshold"
+ "maxSingleShuffleLimit: " + this.maxSingleShuffleLimit
+ "mergeThreshold: " + this.mergeThreshold);
}
boolean allowMemToMemMerge =
jobConf.getBoolean(MRJobConfig.REDUCE_MEMTOMEM_ENABLED, false);
if (allowMemToMemMerge) {
this.memToMemMerger =
new IntermediateMemoryToMemoryMerger(this,
memToMemMergeOutputsThreshold);
this.memToMemMerger.start();
} else {
this.memToMemMerger = null;
}
this.inMemoryMerger = createInMemoryMerger();
this.inMemoryMerger.start();
this.onDiskMerger = new OnDiskMerger(this);
this.onDiskMerger.start();
this.mergePhase = mergePhase;
}
protected MergeThread<InMemoryMapOutput<K,V>, K,V> createInMemoryMerger() {
return new InMemoryMerger(this);
}
TaskAttemptID getReduceId() {
return reduceId;
}
@VisibleForTesting
ExceptionReporter getExceptionReporter() {
return exceptionReporter;
}
@Override
public void waitForResource() throws InterruptedException {
inMemoryMerger.waitForMerge();
}
private boolean canShuffleToMemory(long requestedSize) {
return (requestedSize < maxSingleShuffleLimit);
}
@Override
public synchronized MapOutput<K,V> reserve(TaskAttemptID mapId,
long requestedSize,
int fetcher
) throws IOException {
if (!canShuffleToMemory(requestedSize)) {
LOG.info(mapId + ": Shuffling to disk since " + requestedSize +
" is greater than maxSingleShuffleLimit (" +
maxSingleShuffleLimit + ")");
return new OnDiskMapOutput<K,V>(mapId, reduceId, this, requestedSize,
jobConf, mapOutputFile, fetcher, true);
}
// Stall shuffle if we are above the memory limit
// It is possible that all threads could just be stalling and not make
// progress at all. This could happen when:
//
// requested size is causing the used memory to go above limit &&
// requested size < singleShuffleLimit &&
// current used size < mergeThreshold (merge will not get triggered)
//
// To avoid this from happening, we allow exactly one thread to go past
// the memory limit. We check (usedMemory > memoryLimit) and not
// (usedMemory + requestedSize > memoryLimit). When this thread is done
// fetching, this will automatically trigger a merge thereby unlocking
// all the stalled threads
if (usedMemory > memoryLimit) {
LOG.debug(mapId + ": Stalling shuffle since usedMemory (" + usedMemory
+ ") is greater than memoryLimit (" + memoryLimit + ")." +
" CommitMemory is (" + commitMemory + ")");
return null;
}
// Allow the in-memory shuffle to progress
LOG.debug(mapId + ": Proceeding with shuffle since usedMemory ("
+ usedMemory + ") is lesser than memoryLimit (" + memoryLimit + ")."
+ "CommitMemory is (" + commitMemory + ")");
return unconditionalReserve(mapId, requestedSize, true);
}
/**
* Unconditional Reserve is used by the Memory-to-Memory thread
* @return
*/
private synchronized InMemoryMapOutput<K, V> unconditionalReserve(
TaskAttemptID mapId, long requestedSize, boolean primaryMapOutput) {
usedMemory += requestedSize;
return new InMemoryMapOutput<K,V>(jobConf, mapId, this, (int)requestedSize,
codec, primaryMapOutput);
}
synchronized void unreserve(long size) {
usedMemory -= size;
}
public synchronized void closeInMemoryFile(InMemoryMapOutput<K,V> mapOutput) {
inMemoryMapOutputs.add(mapOutput);
LOG.info("closeInMemoryFile -> map-output of size: " + mapOutput.getSize()
+ ", inMemoryMapOutputs.size() -> " + inMemoryMapOutputs.size()
+ ", commitMemory -> " + commitMemory + ", usedMemory ->" + usedMemory);
commitMemory+= mapOutput.getSize();
// Can hang if mergeThreshold is really low.
if (commitMemory >= mergeThreshold) {
LOG.info("Starting inMemoryMerger's merge since commitMemory=" +
commitMemory + " > mergeThreshold=" + mergeThreshold +
". Current usedMemory=" + usedMemory);
inMemoryMapOutputs.addAll(inMemoryMergedMapOutputs);
inMemoryMergedMapOutputs.clear();
inMemoryMerger.startMerge(inMemoryMapOutputs);
commitMemory = 0L; // Reset commitMemory.
}
if (memToMemMerger != null) {
if (inMemoryMapOutputs.size() >= memToMemMergeOutputsThreshold) {
memToMemMerger.startMerge(inMemoryMapOutputs);
}
}
}
public synchronized void closeInMemoryMergedFile(InMemoryMapOutput<K,V> mapOutput) {
inMemoryMergedMapOutputs.add(mapOutput);
LOG.info("closeInMemoryMergedFile -> size: " + mapOutput.getSize() +
", inMemoryMergedMapOutputs.size() -> " +
inMemoryMergedMapOutputs.size());
}
public synchronized void closeOnDiskFile(CompressAwarePath file) {
onDiskMapOutputs.add(file);
if (onDiskMapOutputs.size() >= (2 * ioSortFactor - 1)) {
onDiskMerger.startMerge(onDiskMapOutputs);
}
}
@Override
public RawKeyValueIterator close() throws Throwable {
// Wait for on-going merges to complete
if (memToMemMerger != null) {
memToMemMerger.close();
}
inMemoryMerger.close();
onDiskMerger.close();
List<InMemoryMapOutput<K, V>> memory =
new ArrayList<InMemoryMapOutput<K, V>>(inMemoryMergedMapOutputs);
inMemoryMergedMapOutputs.clear();
memory.addAll(inMemoryMapOutputs);
inMemoryMapOutputs.clear();
List<CompressAwarePath> disk = new ArrayList<CompressAwarePath>(onDiskMapOutputs);
onDiskMapOutputs.clear();
return finalMerge(jobConf, rfs, memory, disk);
}
private class IntermediateMemoryToMemoryMerger
extends MergeThread<InMemoryMapOutput<K, V>, K, V> {
public IntermediateMemoryToMemoryMerger(MergeManagerImpl<K, V> manager,
int mergeFactor) {
super(manager, mergeFactor, exceptionReporter);
setName("InMemoryMerger - Thread to do in-memory merge of in-memory " +
"shuffled map-outputs");
setDaemon(true);
}
@Override
public void merge(List<InMemoryMapOutput<K, V>> inputs) throws IOException {
if (inputs == null || inputs.size() == 0) {
return;
}
TaskAttemptID dummyMapId = inputs.get(0).getMapId();
List<Segment<K, V>> inMemorySegments = new ArrayList<Segment<K, V>>();
long mergeOutputSize =
createInMemorySegments(inputs, inMemorySegments, 0);
int noInMemorySegments = inMemorySegments.size();
InMemoryMapOutput<K, V> mergedMapOutputs =
unconditionalReserve(dummyMapId, mergeOutputSize, false);
Writer<K, V> writer =
new InMemoryWriter<K, V>(mergedMapOutputs.getArrayStream());
LOG.info("Initiating Memory-to-Memory merge with " + noInMemorySegments +
" segments of total-size: " + mergeOutputSize);
RawKeyValueIterator rIter =
Merger.merge(jobConf, rfs,
(Class<K>)jobConf.getMapOutputKeyClass(),
(Class<V>)jobConf.getMapOutputValueClass(),
inMemorySegments, inMemorySegments.size(),
new Path(reduceId.toString()),
(RawComparator<K>)jobConf.getOutputKeyComparator(),
reporter, null, null, null);
Merger.writeFile(rIter, writer, reporter, jobConf);
writer.close();
LOG.info(reduceId +
" Memory-to-Memory merge of the " + noInMemorySegments +
" files in-memory complete.");
// Note the output of the merge
closeInMemoryMergedFile(mergedMapOutputs);
}
}
private class InMemoryMerger extends MergeThread<InMemoryMapOutput<K,V>, K,V> {
public InMemoryMerger(MergeManagerImpl<K, V> manager) {
super(manager, Integer.MAX_VALUE, exceptionReporter);
setName
("InMemoryMerger - Thread to merge in-memory shuffled map-outputs");
setDaemon(true);
}
@Override
public void merge(List<InMemoryMapOutput<K,V>> inputs) throws IOException {
if (inputs == null || inputs.size() == 0) {
return;
}
//name this output file same as the name of the first file that is
//there in the current list of inmem files (this is guaranteed to
//be absent on the disk currently. So we don't overwrite a prev.
//created spill). Also we need to create the output file now since
//it is not guaranteed that this file will be present after merge
//is called (we delete empty files as soon as we see them
//in the merge method)
//figure out the mapId
TaskAttemptID mapId = inputs.get(0).getMapId();
TaskID mapTaskId = mapId.getTaskID();
List<Segment<K, V>> inMemorySegments = new ArrayList<Segment<K, V>>();
long mergeOutputSize =
createInMemorySegments(inputs, inMemorySegments,0);
int noInMemorySegments = inMemorySegments.size();
Path outputPath =
mapOutputFile.getInputFileForWrite(mapTaskId,
mergeOutputSize).suffix(
Task.MERGED_OUTPUT_PREFIX);
Writer<K,V> writer =
new Writer<K,V>(jobConf, rfs, outputPath,
(Class<K>) jobConf.getMapOutputKeyClass(),
(Class<V>) jobConf.getMapOutputValueClass(),
codec, null);
RawKeyValueIterator rIter = null;
CompressAwarePath compressAwarePath;
try {
LOG.info("Initiating in-memory merge with " + noInMemorySegments +
" segments...");
rIter = Merger.merge(jobConf, rfs,
(Class<K>)jobConf.getMapOutputKeyClass(),
(Class<V>)jobConf.getMapOutputValueClass(),
inMemorySegments, inMemorySegments.size(),
new Path(reduceId.toString()),
(RawComparator<K>)jobConf.getOutputKeyComparator(),
reporter, spilledRecordsCounter, null, null);
if (null == combinerClass) {
Merger.writeFile(rIter, writer, reporter, jobConf);
} else {
combineCollector.setWriter(writer);
combineAndSpill(rIter, reduceCombineInputCounter);
}
writer.close();
compressAwarePath = new CompressAwarePath(outputPath,
writer.getRawLength(), writer.getCompressedLength());
LOG.info(reduceId +
" Merge of the " + noInMemorySegments +
" files in-memory complete." +
" Local file is " + outputPath + " of size " +
localFS.getFileStatus(outputPath).getLen());
} catch (IOException e) {
//make sure that we delete the ondisk file that we created
//earlier when we invoked cloneFileAttributes
localFS.delete(outputPath, true);
throw e;
}
// Note the output of the merge
closeOnDiskFile(compressAwarePath);
}
}
private class OnDiskMerger extends MergeThread<CompressAwarePath,K,V> {
public OnDiskMerger(MergeManagerImpl<K, V> manager) {
super(manager, ioSortFactor, exceptionReporter);
setName("OnDiskMerger - Thread to merge on-disk map-outputs");
setDaemon(true);
}
@Override
public void merge(List<CompressAwarePath> inputs) throws IOException {
// sanity check
if (inputs == null || inputs.isEmpty()) {
LOG.info("No ondisk files to merge...");
return;
}
long approxOutputSize = 0;
int bytesPerSum =
jobConf.getInt("io.bytes.per.checksum", 512);
LOG.info("OnDiskMerger: We have " + inputs.size() +
" map outputs on disk. Triggering merge...");
// 1. Prepare the list of files to be merged.
for (CompressAwarePath file : inputs) {
approxOutputSize += localFS.getFileStatus(file).getLen();
}
// add the checksum length
approxOutputSize +=
ChecksumFileSystem.getChecksumLength(approxOutputSize, bytesPerSum);
// 2. Start the on-disk merge process
Path outputPath =
localDirAllocator.getLocalPathForWrite(inputs.get(0).toString(),
approxOutputSize, jobConf).suffix(Task.MERGED_OUTPUT_PREFIX);
Writer<K,V> writer =
new Writer<K,V>(jobConf, rfs, outputPath,
(Class<K>) jobConf.getMapOutputKeyClass(),
(Class<V>) jobConf.getMapOutputValueClass(),
codec, null);
RawKeyValueIterator iter = null;
CompressAwarePath compressAwarePath;
Path tmpDir = new Path(reduceId.toString());
try {
iter = Merger.merge(jobConf, rfs,
(Class<K>) jobConf.getMapOutputKeyClass(),
(Class<V>) jobConf.getMapOutputValueClass(),
codec, inputs.toArray(new Path[inputs.size()]),
true, ioSortFactor, tmpDir,
(RawComparator<K>) jobConf.getOutputKeyComparator(),
reporter, spilledRecordsCounter, null,
mergedMapOutputsCounter, null);
Merger.writeFile(iter, writer, reporter, jobConf);
writer.close();
compressAwarePath = new CompressAwarePath(outputPath,
writer.getRawLength(), writer.getCompressedLength());
} catch (IOException e) {
localFS.delete(outputPath, true);
throw e;
}
closeOnDiskFile(compressAwarePath);
LOG.info(reduceId +
" Finished merging " + inputs.size() +
" map output files on disk of total-size " +
approxOutputSize + "." +
" Local output file is " + outputPath + " of size " +
localFS.getFileStatus(outputPath).getLen());
}
}
private void combineAndSpill(
RawKeyValueIterator kvIter,
Counters.Counter inCounter) throws IOException {
JobConf job = jobConf;
Reducer combiner = ReflectionUtils.newInstance(combinerClass, job);
Class<K> keyClass = (Class<K>) job.getMapOutputKeyClass();
Class<V> valClass = (Class<V>) job.getMapOutputValueClass();
RawComparator<K> comparator =
(RawComparator<K>)job.getOutputKeyComparator();
try {
CombineValuesIterator values = new CombineValuesIterator(
kvIter, comparator, keyClass, valClass, job, Reporter.NULL,
inCounter);
while (values.more()) {
combiner.reduce(values.getKey(), values, combineCollector,
Reporter.NULL);
values.nextKey();
}
} finally {
combiner.close();
}
}
private long createInMemorySegments(List<InMemoryMapOutput<K,V>> inMemoryMapOutputs,
List<Segment<K, V>> inMemorySegments,
long leaveBytes
) throws IOException {
long totalSize = 0L;
// We could use fullSize could come from the RamManager, but files can be
// closed but not yet present in inMemoryMapOutputs
long fullSize = 0L;
for (InMemoryMapOutput<K,V> mo : inMemoryMapOutputs) {
fullSize += mo.getMemory().length;
}
while(fullSize > leaveBytes) {
InMemoryMapOutput<K,V> mo = inMemoryMapOutputs.remove(0);
byte[] data = mo.getMemory();
long size = data.length;
totalSize += size;
fullSize -= size;
Reader<K,V> reader = new InMemoryReader<K,V>(MergeManagerImpl.this,
mo.getMapId(),
data, 0, (int)size, jobConf);
inMemorySegments.add(new Segment<K,V>(reader, true,
(mo.isPrimaryMapOutput() ?
mergedMapOutputsCounter : null)));
}
return totalSize;
}
class RawKVIteratorReader extends IFile.Reader<K,V> {
private final RawKeyValueIterator kvIter;
public RawKVIteratorReader(RawKeyValueIterator kvIter, long size)
throws IOException {
super(null, null, size, null, spilledRecordsCounter);
this.kvIter = kvIter;
}
public boolean nextRawKey(DataInputBuffer key) throws IOException {
if (kvIter.next()) {
final DataInputBuffer kb = kvIter.getKey();
final int kp = kb.getPosition();
final int klen = kb.getLength() - kp;
key.reset(kb.getData(), kp, klen);
bytesRead += klen;
return true;
}
return false;
}
public void nextRawValue(DataInputBuffer value) throws IOException {
final DataInputBuffer vb = kvIter.getValue();
final int vp = vb.getPosition();
final int vlen = vb.getLength() - vp;
value.reset(vb.getData(), vp, vlen);
bytesRead += vlen;
}
public long getPosition() throws IOException {
return bytesRead;
}
public void close() throws IOException {
kvIter.close();
}
}
private RawKeyValueIterator finalMerge(JobConf job, FileSystem fs,
List<InMemoryMapOutput<K,V>> inMemoryMapOutputs,
List<CompressAwarePath> onDiskMapOutputs
) throws IOException {
LOG.info("finalMerge called with " +
inMemoryMapOutputs.size() + " in-memory map-outputs and " +
onDiskMapOutputs.size() + " on-disk map-outputs");
final float maxRedPer =
job.getFloat(MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT, 0f);
if (maxRedPer > 1.0 || maxRedPer < 0.0) {
throw new IOException(MRJobConfig.REDUCE_INPUT_BUFFER_PERCENT +
maxRedPer);
}
int maxInMemReduce = (int)Math.min(
Runtime.getRuntime().maxMemory() * maxRedPer, Integer.MAX_VALUE);
// merge config params
Class<K> keyClass = (Class<K>)job.getMapOutputKeyClass();
Class<V> valueClass = (Class<V>)job.getMapOutputValueClass();
boolean keepInputs = job.getKeepFailedTaskFiles();
final Path tmpDir = new Path(reduceId.toString());
final RawComparator<K> comparator =
(RawComparator<K>)job.getOutputKeyComparator();
// segments required to vacate memory
List<Segment<K,V>> memDiskSegments = new ArrayList<Segment<K,V>>();
long inMemToDiskBytes = 0;
boolean mergePhaseFinished = false;
if (inMemoryMapOutputs.size() > 0) {
TaskID mapId = inMemoryMapOutputs.get(0).getMapId().getTaskID();
inMemToDiskBytes = createInMemorySegments(inMemoryMapOutputs,
memDiskSegments,
maxInMemReduce);
final int numMemDiskSegments = memDiskSegments.size();
if (numMemDiskSegments > 0 &&
ioSortFactor > onDiskMapOutputs.size()) {
// If we reach here, it implies that we have less than io.sort.factor
// disk segments and this will be incremented by 1 (result of the
// memory segments merge). Since this total would still be
// <= io.sort.factor, we will not do any more intermediate merges,
// the merge of all these disk segments would be directly fed to the
// reduce method
mergePhaseFinished = true;
// must spill to disk, but can't retain in-mem for intermediate merge
final Path outputPath =
mapOutputFile.getInputFileForWrite(mapId,
inMemToDiskBytes).suffix(
Task.MERGED_OUTPUT_PREFIX);
final RawKeyValueIterator rIter = Merger.merge(job, fs,
keyClass, valueClass, memDiskSegments, numMemDiskSegments,
tmpDir, comparator, reporter, spilledRecordsCounter, null,
mergePhase);
Writer<K,V> writer = new Writer<K,V>(job, fs, outputPath,
keyClass, valueClass, codec, null);
try {
Merger.writeFile(rIter, writer, reporter, job);
writer.close();
onDiskMapOutputs.add(new CompressAwarePath(outputPath,
writer.getRawLength(), writer.getCompressedLength()));
writer = null;
// add to list of final disk outputs.
} catch (IOException e) {
if (null != outputPath) {
try {
fs.delete(outputPath, true);
} catch (IOException ie) {
// NOTHING
}
}
throw e;
} finally {
if (null != writer) {
writer.close();
}
}
LOG.info("Merged " + numMemDiskSegments + " segments, " +
inMemToDiskBytes + " bytes to disk to satisfy " +
"reduce memory limit");
inMemToDiskBytes = 0;
memDiskSegments.clear();
} else if (inMemToDiskBytes != 0) {
LOG.info("Keeping " + numMemDiskSegments + " segments, " +
inMemToDiskBytes + " bytes in memory for " +
"intermediate, on-disk merge");
}
}
// segments on disk
List<Segment<K,V>> diskSegments = new ArrayList<Segment<K,V>>();
long onDiskBytes = inMemToDiskBytes;
long rawBytes = inMemToDiskBytes;
CompressAwarePath[] onDisk = onDiskMapOutputs.toArray(
new CompressAwarePath[onDiskMapOutputs.size()]);
for (CompressAwarePath file : onDisk) {
long fileLength = fs.getFileStatus(file).getLen();
onDiskBytes += fileLength;
rawBytes += (file.getRawDataLength() > 0) ? file.getRawDataLength() : fileLength;
LOG.debug("Disk file: " + file + " Length is " + fileLength);
diskSegments.add(new Segment<K, V>(job, fs, file, codec, keepInputs,
(file.toString().endsWith(
Task.MERGED_OUTPUT_PREFIX) ?
null : mergedMapOutputsCounter), file.getRawDataLength()
));
}
LOG.info("Merging " + onDisk.length + " files, " +
onDiskBytes + " bytes from disk");
Collections.sort(diskSegments, new Comparator<Segment<K,V>>() {
public int compare(Segment<K, V> o1, Segment<K, V> o2) {
if (o1.getLength() == o2.getLength()) {
return 0;
}
return o1.getLength() < o2.getLength() ? -1 : 1;
}
});
// build final list of segments from merged backed by disk + in-mem
List<Segment<K,V>> finalSegments = new ArrayList<Segment<K,V>>();
long inMemBytes = createInMemorySegments(inMemoryMapOutputs,
finalSegments, 0);
LOG.info("Merging " + finalSegments.size() + " segments, " +
inMemBytes + " bytes from memory into reduce");
if (0 != onDiskBytes) {
final int numInMemSegments = memDiskSegments.size();
diskSegments.addAll(0, memDiskSegments);
memDiskSegments.clear();
// Pass mergePhase only if there is a going to be intermediate
// merges. See comment where mergePhaseFinished is being set
Progress thisPhase = (mergePhaseFinished) ? null : mergePhase;
RawKeyValueIterator diskMerge = Merger.merge(
job, fs, keyClass, valueClass, codec, diskSegments,
ioSortFactor, numInMemSegments, tmpDir, comparator,
reporter, false, spilledRecordsCounter, null, thisPhase);
diskSegments.clear();
if (0 == finalSegments.size()) {
return diskMerge;
}
finalSegments.add(new Segment<K,V>(
new RawKVIteratorReader(diskMerge, onDiskBytes), true, rawBytes));
}
return Merger.merge(job, fs, keyClass, valueClass,
finalSegments, finalSegments.size(), tmpDir,
comparator, reporter, spilledRecordsCounter, null,
null);
}
static class CompressAwarePath extends Path {
private long rawDataLength;
private long compressedSize;
public CompressAwarePath(Path path, long rawDataLength, long compressSize) {
super(path.toUri());
this.rawDataLength = rawDataLength;
this.compressedSize = compressSize;
}
public long getRawDataLength() {
return rawDataLength;
}
public long getCompressedSize() {
return compressedSize;
}
@Override
public boolean equals(Object other) {
return super.equals(other);
}
@Override
public int hashCode() {
return super.hashCode();
}
@Override
public int compareTo(Object obj) {
if(obj instanceof CompressAwarePath) {
CompressAwarePath compPath = (CompressAwarePath) obj;
if(this.compressedSize < compPath.getCompressedSize()) {
return -1;
} else if (this.getCompressedSize() > compPath.getCompressedSize()) {
return 1;
}
// Not returning 0 here so that objects with the same size (but
// different paths) are still added to the TreeSet.
}
return super.compareTo(obj);
}
}
}