/*
* Cloud9: A MapReduce Library for Hadoop
*
* Licensed 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 edu.umd.cloud9.example.simple;
import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
import org.apache.log4j.Logger;
import tl.lin.data.JsonWritable;
/**
* Modified word count demo designed to work with {@link DemoPackJson}. Counts words on even-length
* or odd-length lines to demonstrate use of specialized intermediate data structures.
*
* @author Jimmy Lin
*/
public class DemoWordCountJson extends Configured implements Tool {
private static final Logger LOG = Logger.getLogger(DemoWordCountJson.class);
// Define custom intermediate key; must specify sort order.
public static class MyKey extends JsonWritable implements WritableComparable<MyKey> {
public int compareTo(MyKey that) {
String thisToken = this.getJsonObject().get("Token").getAsString();
String thatToken = that.getJsonObject().get("Token").getAsString();
// If tokens are equal, must check "EvenOrOdd" field.
if (thisToken.equals(thatToken)) {
// Otherwise, sort by "EvenOrOdd" field.
int thisEO = this.getJsonObject().get("EvenOrOdd").getAsInt();
int thatEO = that.getJsonObject().get("EvenOrOdd").getAsInt();
if (thisEO < thatEO)
return -1;
if (thisEO > thatEO)
return 1;
// If we get here, it means the tuples are equal.
return 0;
}
// Determine sort order based on token.
return thisToken.compareTo(thatToken);
}
public int hashCode() {
return this.getJsonObject().getAsJsonPrimitive("Token").getAsString().hashCode();
}
}
// Mapper: emits a JSON object as the key, and value '1' for each occurrence.
protected static class MyMapper extends Mapper<LongWritable, JsonWritable, MyKey, IntWritable> {
private final static IntWritable ONE = new IntWritable(1);
private final static MyKey KEY = new MyKey();
@Override
public void map(LongWritable dummy, JsonWritable jsonIn, Context context)
throws IOException, InterruptedException {
String line = (String) jsonIn.getJsonObject().get("text").getAsString();
StringTokenizer itr = new StringTokenizer(line);
while (itr.hasMoreTokens()) {
String token = itr.nextToken();
// Put new values into the tuple.
KEY.getJsonObject().addProperty("Token", token);
KEY.getJsonObject().addProperty("EvenOrOdd", line.length() % 2);
// Emit key-value pair.
context.write(KEY, ONE);
}
}
}
// Reducer counts up tuple occurrences.
protected static class MyReducer extends Reducer<MyKey, IntWritable, MyKey, IntWritable> {
private final static IntWritable SUM = new IntWritable();
@Override
public void reduce(MyKey keyIn, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
Iterator<IntWritable> iter = values.iterator();
int sum = 0;
while (iter.hasNext()) {
sum += iter.next().get();
}
// Keep original tuple key, emit sum of counts as value.
SUM.set(sum);
context.write(keyIn, SUM);
}
}
/**
* Creates an instance of this tool.
*/
public DemoWordCountJson() {}
private static int printUsage() {
System.out.println("usage: [input-path] [output-path] [num-reducers]");
ToolRunner.printGenericCommandUsage(System.out);
return -1;
}
/**
* Runs this tool.
*/
public int run(String[] args) throws Exception {
if (args.length != 3) {
printUsage();
return -1;
}
String inputPath = args[0];
String outputPath = args[1];
int numReduceTasks = Integer.parseInt(args[2]);
LOG.info("Tool: " + DemoWordCountJson.class.getSimpleName());
LOG.info(" - input path: " + inputPath);
LOG.info(" - output path: " + outputPath);
LOG.info(" - number of reducers: " + numReduceTasks);
Configuration conf = getConf();
Job job = Job.getInstance(conf);
job.setJobName(DemoWordCountJson.class.getSimpleName());
job.setJarByClass(DemoWordCountJson.class);
job.setNumReduceTasks(numReduceTasks);
FileInputFormat.setInputPaths(job, new Path(inputPath));
FileOutputFormat.setOutputPath(job, new Path(outputPath));
job.setInputFormatClass(SequenceFileInputFormat.class);
job.setOutputFormatClass(SequenceFileOutputFormat.class);
job.setOutputKeyClass(MyKey.class);
job.setOutputValueClass(IntWritable.class);
job.setMapperClass(MyMapper.class);
job.setCombinerClass(MyReducer.class);
job.setReducerClass(MyReducer.class);
// Delete the output directory if it exists already.
Path outputDir = new Path(outputPath);
FileSystem.get(conf).delete(outputDir, true);
long startTime = System.currentTimeMillis();
job.waitForCompletion(true);
LOG.info("Job Finished in " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
return 0;
}
/**
* Dispatches command-line arguments to the tool via the {@code ToolRunner}.
*/
public static void main(String[] args) throws Exception {
ToolRunner.run(new DemoWordCountJson(), args);
}
}