/**
* 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.examples.terasort;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.MRJobConfig;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.TaskAttemptID;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl;
import org.apache.hadoop.util.IndexedSortable;
import org.apache.hadoop.util.QuickSort;
import org.apache.hadoop.util.StringUtils;
/**
* An input format that reads the first 10 characters of each line as the key
* and the rest of the line as the value. Both key and value are represented
* as Text.
*/
public class TeraInputFormat extends FileInputFormat<Text,Text> {
static final String PARTITION_FILENAME = "_partition.lst";
private static final String NUM_PARTITIONS =
"mapreduce.terasort.num.partitions";
private static final String SAMPLE_SIZE =
"mapreduce.terasort.partitions.sample";
static final int KEY_LENGTH = 10;
static final int VALUE_LENGTH = 90;
static final int RECORD_LENGTH = KEY_LENGTH + VALUE_LENGTH;
private static MRJobConfig lastContext = null;
private static List<InputSplit> lastResult = null;
static class TextSampler implements IndexedSortable {
private ArrayList<Text> records = new ArrayList<Text>();
public int compare(int i, int j) {
Text left = records.get(i);
Text right = records.get(j);
return left.compareTo(right);
}
public void swap(int i, int j) {
Text left = records.get(i);
Text right = records.get(j);
records.set(j, left);
records.set(i, right);
}
public void addKey(Text key) {
synchronized (this) {
records.add(new Text(key));
}
}
/**
* Find the split points for a given sample. The sample keys are sorted
* and down sampled to find even split points for the partitions. The
* returned keys should be the start of their respective partitions.
* @param numPartitions the desired number of partitions
* @return an array of size numPartitions - 1 that holds the split points
*/
Text[] createPartitions(int numPartitions) {
int numRecords = records.size();
System.out.println("Making " + numPartitions + " from " + numRecords +
" sampled records");
if (numPartitions > numRecords) {
throw new IllegalArgumentException
("Requested more partitions than input keys (" + numPartitions +
" > " + numRecords + ")");
}
new QuickSort().sort(this, 0, records.size());
float stepSize = numRecords / (float) numPartitions;
Text[] result = new Text[numPartitions-1];
for(int i=1; i < numPartitions; ++i) {
result[i-1] = records.get(Math.round(stepSize * i));
}
return result;
}
}
/**
* Use the input splits to take samples of the input and generate sample
* keys. By default reads 100,000 keys from 10 locations in the input, sorts
* them and picks N-1 keys to generate N equally sized partitions.
* @param job the job to sample
* @param partFile where to write the output file to
* @throws Throwable if something goes wrong
*/
public static void writePartitionFile(final JobContext job,
Path partFile) throws Throwable {
long t1 = System.currentTimeMillis();
Configuration conf = job.getConfiguration();
final TeraInputFormat inFormat = new TeraInputFormat();
final TextSampler sampler = new TextSampler();
int partitions = job.getNumReduceTasks();
long sampleSize = conf.getLong(SAMPLE_SIZE, 100000);
final List<InputSplit> splits = inFormat.getSplits(job);
long t2 = System.currentTimeMillis();
System.out.println("Computing input splits took " + (t2 - t1) + "ms");
int samples = Math.min(conf.getInt(NUM_PARTITIONS, 10), splits.size());
System.out.println("Sampling " + samples + " splits of " + splits.size());
final long recordsPerSample = sampleSize / samples;
final int sampleStep = splits.size() / samples;
Thread[] samplerReader = new Thread[samples];
SamplerThreadGroup threadGroup = new SamplerThreadGroup("Sampler Reader Thread Group");
// take N samples from different parts of the input
for(int i=0; i < samples; ++i) {
final int idx = i;
samplerReader[i] =
new Thread (threadGroup,"Sampler Reader " + idx) {
{
setDaemon(true);
}
public void run() {
long records = 0;
try {
TaskAttemptContext context = new TaskAttemptContextImpl(
job.getConfiguration(), new TaskAttemptID());
RecordReader<Text, Text> reader =
inFormat.createRecordReader(splits.get(sampleStep * idx),
context);
reader.initialize(splits.get(sampleStep * idx), context);
while (reader.nextKeyValue()) {
sampler.addKey(new Text(reader.getCurrentKey()));
records += 1;
if (recordsPerSample <= records) {
break;
}
}
} catch (IOException ie){
System.err.println("Got an exception while reading splits " +
StringUtils.stringifyException(ie));
throw new RuntimeException(ie);
} catch (InterruptedException e) {
}
}
};
samplerReader[i].start();
}
FileSystem outFs = partFile.getFileSystem(conf);
DataOutputStream writer = outFs.create(partFile, true, 64*1024, (short) 10,
outFs.getDefaultBlockSize(partFile));
for (int i = 0; i < samples; i++) {
try {
samplerReader[i].join();
if(threadGroup.getThrowable() != null){
throw threadGroup.getThrowable();
}
} catch (InterruptedException e) {
}
}
for(Text split : sampler.createPartitions(partitions)) {
split.write(writer);
}
writer.close();
long t3 = System.currentTimeMillis();
System.out.println("Computing parititions took " + (t3 - t2) + "ms");
}
static class SamplerThreadGroup extends ThreadGroup{
private Throwable throwable;
public SamplerThreadGroup(String s) {
super(s);
}
@Override
public void uncaughtException(Thread thread, Throwable throwable) {
this.throwable = throwable;
}
public Throwable getThrowable() {
return this.throwable;
}
}
static class TeraRecordReader extends RecordReader<Text,Text> {
private FSDataInputStream in;
private long offset;
private long length;
private static final int RECORD_LENGTH = KEY_LENGTH + VALUE_LENGTH;
private byte[] buffer = new byte[RECORD_LENGTH];
private Text key;
private Text value;
public TeraRecordReader() throws IOException {
}
public void initialize(InputSplit split, TaskAttemptContext context)
throws IOException, InterruptedException {
Path p = ((FileSplit)split).getPath();
FileSystem fs = p.getFileSystem(context.getConfiguration());
in = fs.open(p);
long start = ((FileSplit)split).getStart();
// find the offset to start at a record boundary
offset = (RECORD_LENGTH - (start % RECORD_LENGTH)) % RECORD_LENGTH;
in.seek(start + offset);
length = ((FileSplit)split).getLength();
}
public void close() throws IOException {
in.close();
}
public Text getCurrentKey() {
return key;
}
public Text getCurrentValue() {
return value;
}
public float getProgress() throws IOException {
return (float) offset / length;
}
public boolean nextKeyValue() throws IOException {
if (offset >= length) {
return false;
}
int read = 0;
while (read < RECORD_LENGTH) {
long newRead = in.read(buffer, read, RECORD_LENGTH - read);
if (newRead == -1) {
if (read == 0) {
return false;
} else {
throw new EOFException("read past eof");
}
}
read += newRead;
}
if (key == null) {
key = new Text();
}
if (value == null) {
value = new Text();
}
key.set(buffer, 0, KEY_LENGTH);
value.set(buffer, KEY_LENGTH, VALUE_LENGTH);
offset += RECORD_LENGTH;
return true;
}
}
@Override
public RecordReader<Text, Text>
createRecordReader(InputSplit split, TaskAttemptContext context)
throws IOException {
return new TeraRecordReader();
}
@Override
public List<InputSplit> getSplits(JobContext job) throws IOException {
if (job == lastContext) {
return lastResult;
}
long t1, t2, t3;
t1 = System.currentTimeMillis();
lastContext = job;
lastResult = super.getSplits(job);
t2 = System.currentTimeMillis();
System.out.println("Spent " + (t2 - t1) + "ms computing base-splits.");
if (job.getConfiguration().getBoolean(TeraScheduler.USE, true)) {
TeraScheduler scheduler = new TeraScheduler(
lastResult.toArray(new FileSplit[0]), job.getConfiguration());
lastResult = scheduler.getNewFileSplits();
t3 = System.currentTimeMillis();
System.out.println("Spent " + (t3 - t2) + "ms computing TeraScheduler splits.");
}
return lastResult;
}
}