com.phantom.hadoop.examples.terasort.TeraChecksum.java Source code

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Here is the source code for com.phantom.hadoop.examples.terasort.TeraChecksum.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 com.phantom.hadoop.examples.terasort;

import java.io.IOException;
import java.util.zip.Checksum;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.util.PureJavaCrc32;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

public class TeraChecksum extends Configured implements Tool {
    static class ChecksumMapper extends Mapper<Text, Text, NullWritable, Unsigned16> {
        private Unsigned16 checksum = new Unsigned16();
        private Unsigned16 sum = new Unsigned16();
        private Checksum crc32 = new PureJavaCrc32();

        public void map(Text key, Text value, Context context) throws IOException {
            crc32.reset();
            crc32.update(key.getBytes(), 0, key.getLength());
            crc32.update(value.getBytes(), 0, value.getLength());
            checksum.set(crc32.getValue());
            sum.add(checksum);
        }

        public void cleanup(Context context) throws IOException, InterruptedException {
            context.write(NullWritable.get(), sum);
        }
    }

    static class ChecksumReducer extends Reducer<NullWritable, Unsigned16, NullWritable, Unsigned16> {

        public void reduce(NullWritable key, Iterable<Unsigned16> values, Context context)
                throws IOException, InterruptedException {
            Unsigned16 sum = new Unsigned16();
            for (Unsigned16 val : values) {
                sum.add(val);
            }
            context.write(key, sum);
        }
    }

    private static void usage() throws IOException {
        System.err.println("terasum <out-dir> <report-dir>");
    }

    public int run(String[] args) throws Exception {
        Job job = Job.getInstance(getConf());
        if (args.length != 2) {
            usage();
            return 2;
        }
        TeraInputFormat.setInputPaths(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        job.setJobName("TeraSum");
        job.setJarByClass(TeraChecksum.class);
        job.setMapperClass(ChecksumMapper.class);
        job.setReducerClass(ChecksumReducer.class);
        job.setOutputKeyClass(NullWritable.class);
        job.setOutputValueClass(Unsigned16.class);
        // force a single reducer
        job.setNumReduceTasks(1);
        job.setInputFormatClass(TeraInputFormat.class);
        return job.waitForCompletion(true) ? 0 : 1;
    }

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

}