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

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Here is the source code for com.github.ygf.pagerank.InLinks.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 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.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.SequenceFileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class InLinks extends Configured implements Tool {

    private void computeInLinks(Configuration conf, Path linksFile, Path outputDir) throws Exception {

        // This job computes the number of in-links for every page. The
        // implementation is very similar to the classic word count example.

        Job job = Job.getInstance(conf, "InLinks:Computation");

        job.setJarByClass(InLinks.class);
        job.setInputFormatClass(TextInputFormat.class);
        job.setMapperClass(InLinksMapper.class);
        job.setCombinerClass(InLinksReducer.class);
        job.setReducerClass(InLinksReducer.class);
        job.setOutputFormatClass(SequenceFileOutputFormat.class);
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, linksFile);
        FileOutputFormat.setOutputPath(job, new Path(outputDir, "inlinks"));

        job.waitForCompletion(true);
    }

    private void summarizeResults(Configuration conf, Path outputDir) throws Exception {

        int topResults = Integer.parseInt(conf.get("inlinks.top_results"));

        Job job = Job.getInstance(conf, "InLinks:TopN");

        job.setJarByClass(InLinks.class);

        job.setInputFormatClass(SequenceFileInputFormat.class);
        job.setMapperClass(InLinksTopNMapper.class);
        job.setMapOutputKeyClass(IntWritable.class);
        job.setMapOutputValueClass(IntWritable.class);
        job.setReducerClass(InLinksTopNReducer.class);
        job.setOutputFormatClass(TextOutputFormat.class);
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(outputDir, "inlinks"));
        FileOutputFormat.setOutputPath(job, new Path(outputDir, "inlinks-top" + topResults));

        job.setNumReduceTasks(1);
        job.waitForCompletion(true);
    }

    public int run(String[] args) throws Exception {
        if (args.length != 3) {
            System.out.println("Usage: InLinks <links-simple-sorted.txt> <titles-dir> <output-dir>");
            ToolRunner.printGenericCommandUsage(System.out);
            return 2;
        }

        Path linksFile = new Path(args[0]);
        Path titlesDir = new Path(args[1]);
        Path outputDir = new Path(args[2]);

        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");

        // Default values of the parameters of the algorithm.
        conf.setInt("inlinks.top_results", conf.getInt("inlinks.top_results", 100));

        conf.set("inlinks.titles_dir", titlesDir.toString());

        computeInLinks(conf, linksFile, outputDir);
        summarizeResults(conf, outputDir);

        return 0;
    }

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