com.github.ygf.pagerank.TitleIndex.java Source code

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Here is the source code for com.github.ygf.pagerank.TitleIndex.java

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/*
 * Copyright 2014 Yasser Gonzalez Fernandez <ygonzalezfernandez@gmail.com>.
 * 
 * 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.github.ygf.pagerank;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.MapFileOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class TitleIndex extends Configured implements Tool {

    public static class TitleIndexMapper extends Mapper<LongWritable, Text, IntWritable, Text> {

        int lineNum = 0;

        @Override
        public void map(LongWritable inKey, Text inValue, Context context)
                throws IOException, InterruptedException {
            context.write(new IntWritable(++lineNum), inValue);
        }
    }

    public int run(String[] args) throws Exception {
        if (args.length != 2) {
            System.out.println("Usage: TitleIndex <titles-sorted.txt> <output-dir>");
            ToolRunner.printGenericCommandUsage(System.out);
            return 2;
        }

        Path titlesFile = new Path(args[0]);
        Path outputDir = new Path(args[1]);

        Configuration conf = getConf();

        // Do not create _SUCCESS files. MapFileOutputFormat.getReaders calls
        // try to read the _SUCCESS as another MapFile dir.
        conf.set("mapreduce.fileoutputcommitter.marksuccessfuljobs", "false");

        // This job creates a MapFile of the titles indexed by the page id.
        // UnsplittableTextInputFormat is used to ensure that the same map task
        // gets all the lines in the titlesFile and it can count the line
        // numbers. The number of reduce tasks is set to 0.

        Job job = Job.getInstance(conf, "TitleIndex");

        job.setJarByClass(InLinks.class);
        job.setInputFormatClass(UnsplittableTextInputFormat.class);
        job.setMapperClass(TitleIndexMapper.class);
        job.setOutputFormatClass(MapFileOutputFormat.class);
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(Text.class);
        FileInputFormat.addInputPath(job, titlesFile);
        FileOutputFormat.setOutputPath(job, outputDir);

        job.setNumReduceTasks(0);
        job.waitForCompletion(true);

        return 0;
    }

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