org.asayler.WikiTitleCount.java Source code

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Here is the source code for org.asayler.WikiTitleCount.java

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/**
 * 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.
 *
 * By Andy Sayler
 * 04/2012
 *
 * Adopted from Apache Hadoop WordCount.java example
 * Adopted from Apache Hadoop WPiEstimator.java example
 *
 */

package org.asayler;

import java.io.*;
import java.lang.*;
import java.util.*;

import org.apache.hadoop.fs.*;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.util.*;

/**
 * This is a Hadoop Map/Reduce application.
 * It reads the text input files of Wikipedia article titles, one per line.
 * It then breaks each line into words using '_' deliminators
 * and counts the first word in each title.
 * The output is a locally sorted list of title first words and the 
 * count of how often they occurred.
 * 
 */
public class WikiTitleCount extends Configured implements Tool {

    public static class MapClass extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable> {

        private final static IntWritable one = new IntWritable(1);
        private Text word = new Text();

        public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter)
                throws IOException {
            String line = value.toString();
            String[] titles = line.split("\\s+", 0);
            for (int x = 0; x < titles.length; x++) {
                String[] titlewords = titles[x].split("_", 0);
                /** grab first word */
                word.set(titlewords[0]);
                output.collect(word, one);
            }
        }
    }

    public static class Reduce extends MapReduceBase implements Reducer<Text, IntWritable, Text, IntWritable> {

        public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output,
                Reporter reporter) throws IOException {
            int sum = 0;
            while (values.hasNext()) {
                sum += values.next().get();
            }
            output.collect(key, new IntWritable(sum));
        }
    }

    static int printUsage() {
        System.out.println("wikititlecount <input> <output>");
        ToolRunner.printGenericCommandUsage(System.out);
        return -1;
    }

    /**
     * The main driver for wikititlecount map/reduce program.
     * Invoke this method to submit the map/reduce job.
     * @throws IOException When there is communication problems with the 
     *                     job tracker.
     */
    public int run(String[] args) throws Exception {
        JobConf conf = new JobConf(getConf(), WikiTitleCount.class);
        JobClient client = new JobClient(conf);
        ClusterStatus cluster = client.getClusterStatus();

        int num_maps = 1;
        int num_reducers = 1;

        conf.setJobName("wikititlecount");

        conf.setOutputKeyClass(Text.class);
        conf.setOutputValueClass(IntWritable.class);

        conf.setMapperClass(MapClass.class);
        conf.setCombinerClass(Reduce.class);
        conf.setReducerClass(Reduce.class);

        conf.setInputFormat(TextInputFormat.class);
        conf.setOutputFormat(TextOutputFormat.class);

        /** Set Default Mappers */
        num_maps = (int) (cluster.getMaxMapTasks());

        /** Set Default Mappers */
        num_reducers = (int) (cluster.getMaxReduceTasks() * 0.9);

        List<String> other_args = new ArrayList<String>();
        for (int i = 0; i < args.length; ++i) {
            try {
                other_args.add(args[i]);
            } catch (NumberFormatException except) {
                System.out.println("ERROR: Integer expected instead of " + args[i]);
                return printUsage();
            } catch (ArrayIndexOutOfBoundsException except) {
                System.out.println("ERROR: Required parameter missing from " + args[i - 1]);
                return printUsage();
            }
        }
        // Make sure there are exactly 2 parameters left.
        if (other_args.size() != 2) {
            System.out.println("ERROR: Wrong number of parameters: " + other_args.size() + " instead of 2.");
            return printUsage();
        }
        FileInputFormat.setInputPaths(conf, other_args.get(0));
        FileOutputFormat.setOutputPath(conf, new Path(other_args.get(1)));

        /* Set Mappers and Reducer */
        conf.setNumMapTasks(num_maps);
        conf.setNumReduceTasks(num_reducers);

        JobClient.runJob(conf);
        return 0;
    }

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

}