com.talis.labs.pagerank.mapreduce.SortPageRanks.java Source code

Introduction

Here is the source code for com.talis.labs.pagerank.mapreduce.SortPageRanks.java

Source

/*
 * Copyright  2011 Talis Systems Ltd.
 *
 * 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 com.talis.labs.pagerank.mapreduce;

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.DoubleWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class SortPageRanks extends Configured implements Tool {

    @Override
    public int run(String[] args) throws Exception {
        if (args.length != 2) {
            System.err.println("Usage: SortPageRanks <input path> <output path>");
            return -1;
        }

        FileSystem.get(getConf()).delete(new Path(args[1]), true);

        Job job = new Job(getConf(), "SortPageRanks");
        job.setJarByClass(getClass());

        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        job.setMapperClass(SortPageRanksMapper.class);
        job.setReducerClass(Reducer.class); // i.e. identity reducer
        job.setSortComparatorClass(DoubleWritableDecreasingComparator.class);

        job.setMapOutputKeyClass(DoubleWritable.class);
        job.setMapOutputValueClass(Text.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);

        job.setNumReduceTasks(1); // TODO: inefficient, use InputSampler with v0.20.x

        return job.waitForCompletion(true) ? 0 : 1;
    }

    public static void main(String[] args) throws Exception {
        int exitCode = ToolRunner.run(new Configuration(), new SortPageRanks(), args);
        System.exit(exitCode);
    }

}

class DoubleWritableDecreasingComparator extends DoubleWritable.Comparator {

    @Override
    public int compare(byte[] b1, int s1, int l1, byte[] b2, int s2, int l2) {
        return -super.compare(b1, s1, l1, b2, s2, l2);
    }

}