testshell.ExternalMapReduce.java Source code

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Here is the source code for testshell.ExternalMapReduce.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.
 */

package testshell;

import java.io.IOException;
import java.util.Iterator;

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.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.MapReduceBase;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

/**
 * will be in an external jar and used for 
 * test in TestJobShell.java.
 */
public class ExternalMapReduce extends Configured implements Tool {

    public void configure(JobConf job) {
        // do nothing
    }

    public void close() throws IOException {

    }

    public static class MapClass extends MapReduceBase
            implements Mapper<WritableComparable, Writable, WritableComparable, IntWritable> {
        public void map(WritableComparable key, Writable value,
                OutputCollector<WritableComparable, IntWritable> output, Reporter reporter) throws IOException {
            //check for classpath
            String classpath = System.getProperty("java.class.path");
            if (classpath.indexOf("testjob.jar") == -1) {
                throw new IOException("failed to find in the library " + classpath);
            }
            //fork off ls to see if the file exists.
            // java file.exists() will not work on 
            // cygwin since it is a symlink
            String[] argv = new String[2];
            argv[0] = "ls";
            argv[1] = "files_tmp";
            Process p = Runtime.getRuntime().exec(argv);
            int ret = -1;
            try {
                ret = p.waitFor();
            } catch (InterruptedException ie) {
                //do nothing here.
            }
            if (ret != 0) {
                throw new IOException("files_tmp does not exist");
            }
        }
    }

    public static class Reduce extends MapReduceBase
            implements Reducer<WritableComparable, Writable, WritableComparable, IntWritable> {
        public void reduce(WritableComparable key, Iterator<Writable> values,
                OutputCollector<WritableComparable, IntWritable> output, Reporter reporter) throws IOException {
            //do nothing
        }
    }

    public int run(String[] argv) throws IOException {
        if (argv.length < 2) {
            System.out.println("ExternalMapReduce <input> <output>");
            return -1;
        }
        Path outDir = new Path(argv[1]);
        Path input = new Path(argv[0]);
        JobConf testConf = new JobConf(getConf(), ExternalMapReduce.class);

        //try to load a class from libjar
        try {
            testConf.getClassByName("testjar.ClassWordCount");
        } catch (ClassNotFoundException e) {
            System.out.println("Could not find class from libjar");
            return -1;
        }

        testConf.setJobName("external job");
        FileInputFormat.setInputPaths(testConf, input);
        FileOutputFormat.setOutputPath(testConf, outDir);
        testConf.setMapperClass(MapClass.class);
        testConf.setReducerClass(Reduce.class);
        testConf.setNumReduceTasks(1);
        JobClient.runJob(testConf);
        return 0;
    }

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