com.hadoopilluminated.examples.Grep.java Source code

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Here is the source code for com.hadoopilluminated.examples.Grep.java

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package com.hadoopilluminated.examples;

/**
 * The example below is taken from org.apache.hadoop.examples. It is then
 * commented and modified for the purposes of the book
 */

/**
 * 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.
 */
import java.util.Random;
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.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.mapred.lib.InverseMapper;
import org.apache.hadoop.mapred.lib.LongSumReducer;
import org.apache.hadoop.mapred.lib.RegexMapper;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/*
 * Extracts matching regexs from input files and counts them.
 */
public class Grep extends Configured implements Tool {

    private Grep() {
    } // singleton

    @Override
    public int run(String[] args) throws Exception {
        if (args.length < 3) {
            System.out.println("Grep <inDir> <outDir> <regex> [<group>]");
            ToolRunner.printGenericCommandUsage(System.out);
            return -1;
        }

        Path tempDir = new Path("grep-temp-" + Integer.toString(new Random().nextInt(Integer.MAX_VALUE)));

        JobConf grepJob = new JobConf(getConf(), Grep.class);

        try {

            grepJob.setJobName("grep-search");

            FileInputFormat.setInputPaths(grepJob, args[0]);

            grepJob.setMapperClass(RegexMapper.class);
            grepJob.set("mapred.mapper.regex", args[2]);
            if (args.length == 4) {
                grepJob.set("mapred.mapper.regex.group", args[3]);
            }

            grepJob.setCombinerClass(LongSumReducer.class);
            grepJob.setReducerClass(LongSumReducer.class);

            FileOutputFormat.setOutputPath(grepJob, tempDir);
            grepJob.setOutputFormat(SequenceFileOutputFormat.class);
            grepJob.setOutputKeyClass(Text.class);
            grepJob.setOutputValueClass(LongWritable.class);

            JobClient.runJob(grepJob);

            JobConf sortJob = new JobConf(getConf(), Grep.class);
            sortJob.setJobName("grep-sort");

            FileInputFormat.setInputPaths(sortJob, tempDir);
            sortJob.setInputFormat(SequenceFileInputFormat.class);

            sortJob.setMapperClass(InverseMapper.class);

            sortJob.setNumReduceTasks(1); // write a single file
            FileOutputFormat.setOutputPath(sortJob, new Path(args[1]));
            sortJob.setOutputKeyComparatorClass // sort by decreasing freq
            (LongWritable.DecreasingComparator.class);

            JobClient.runJob(sortJob);
        } finally {
            FileSystem.get(grepJob).delete(tempDir, true);
        }
        return 0;
    }

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