/**
* 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;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.CombineFileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.CombineFileRecordReader;
import org.apache.hadoop.mapreduce.lib.input.CombineFileSplit;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.reduce.IntSumReducer;
import org.apache.hadoop.util.LineReader;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
/**
* MultiFileWordCount is an example to demonstrate the usage of
* MultiFileInputFormat. This examples counts the occurrences of
* words in the text files under the given input directory.
*/
public class MultiFileWordCount extends Configured implements Tool {
/**
* This record keeps <filename,offset> pairs.
*/
public static class WordOffset implements WritableComparable {
private long offset;
private String fileName;
public void readFields(DataInput in) throws IOException {
this.offset = in.readLong();
this.fileName = Text.readString(in);
}
public void write(DataOutput out) throws IOException {
out.writeLong(offset);
Text.writeString(out, fileName);
}
public int compareTo(Object o) {
WordOffset that = (WordOffset)o;
int f = this.fileName.compareTo(that.fileName);
if(f == 0) {
return (int)Math.signum((double)(this.offset - that.offset));
}
return f;
}
@Override
public boolean equals(Object obj) {
if(obj instanceof WordOffset)
return this.compareTo(obj) == 0;
return false;
}
@Override
public int hashCode() {
assert false : "hashCode not designed";
return 42; //an arbitrary constant
}
}
/**
* To use {@link CombineFileInputFormat}, one should extend it, to return a
* (custom) {@link RecordReader}. CombineFileInputFormat uses
* {@link CombineFileSplit}s.
*/
public static class MyInputFormat
extends CombineFileInputFormat<WordOffset, Text> {
public RecordReader<WordOffset,Text> createRecordReader(InputSplit split,
TaskAttemptContext context) throws IOException {
return new CombineFileRecordReader<WordOffset, Text>(
(CombineFileSplit)split, context, CombineFileLineRecordReader.class);
}
}
/**
* RecordReader is responsible from extracting records from a chunk
* of the CombineFileSplit.
*/
public static class CombineFileLineRecordReader
extends RecordReader<WordOffset, Text> {
private long startOffset; //offset of the chunk;
private long end; //end of the chunk;
private long pos; // current pos
private FileSystem fs;
private Path path;
private WordOffset key;
private Text value;
private FSDataInputStream fileIn;
private LineReader reader;
public CombineFileLineRecordReader(CombineFileSplit split,
TaskAttemptContext context, Integer index) throws IOException {
fs = FileSystem.get(context.getConfiguration());
this.path = split.getPath(index);
this.startOffset = split.getOffset(index);
this.end = startOffset + split.getLength(index);
boolean skipFirstLine = false;
//open the file
fileIn = fs.open(path);
if (startOffset != 0) {
skipFirstLine = true;
--startOffset;
fileIn.seek(startOffset);
}
reader = new LineReader(fileIn);
if (skipFirstLine) { // skip first line and re-establish "startOffset".
startOffset += reader.readLine(new Text(), 0,
(int)Math.min((long)Integer.MAX_VALUE, end - startOffset));
}
this.pos = startOffset;
}
public void initialize(InputSplit split, TaskAttemptContext context)
throws IOException, InterruptedException {
}
public void close() throws IOException { }
public float getProgress() throws IOException {
if (startOffset == end) {
return 0.0f;
} else {
return Math.min(1.0f, (pos - startOffset) / (float)(end - startOffset));
}
}
public boolean nextKeyValue() throws IOException {
if (key == null) {
key = new WordOffset();
key.fileName = path.getName();
}
key.offset = pos;
if (value == null) {
value = new Text();
}
int newSize = 0;
if (pos < end) {
newSize = reader.readLine(value);
pos += newSize;
}
if (newSize == 0) {
key = null;
value = null;
return false;
} else {
return true;
}
}
public WordOffset getCurrentKey()
throws IOException, InterruptedException {
return key;
}
public Text getCurrentValue() throws IOException, InterruptedException {
return value;
}
}
/**
* This Mapper is similar to the one in {@link WordCount.MapClass}.
*/
public static class MapClass extends
Mapper<WordOffset, Text, Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(WordOffset key, Text value, Context context)
throws IOException, InterruptedException {
String line = value.toString();
StringTokenizer itr = new StringTokenizer(line);
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
context.write(word, one);
}
}
}
private void printUsage() {
System.out.println("Usage : multifilewc <input_dir> <output>" );
}
public int run(String[] args) throws Exception {
if(args.length < 2) {
printUsage();
return 2;
}
Job job = new Job(getConf());
job.setJobName("MultiFileWordCount");
job.setJarByClass(MultiFileWordCount.class);
//set the InputFormat of the job to our InputFormat
job.setInputFormatClass(MyInputFormat.class);
// the keys are words (strings)
job.setOutputKeyClass(Text.class);
// the values are counts (ints)
job.setOutputValueClass(IntWritable.class);
//use the defined mapper
job.setMapperClass(MapClass.class);
//use the WordCount Reducer
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
FileInputFormat.addInputPaths(job, args[0]);
FileOutputFormat.setOutputPath(job, new Path(args[1]));
return job.waitForCompletion(true) ? 0 : 1;
}
public static void main(String[] args) throws Exception {
int ret = ToolRunner.run(new MultiFileWordCount(), args);
System.exit(ret);
}
}