examples/src/main/java/org/apache/hama/examples/CombineExample.java

/**
 * 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 org.apache.hama.examples;

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

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IOUtils;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hama.HamaConfiguration;
import org.apache.hama.bsp.BSP;
import org.apache.hama.bsp.BSPJob;
import org.apache.hama.bsp.BSPPeer;
import org.apache.hama.bsp.Combiner;
import org.apache.hama.bsp.FileOutputFormat;
import org.apache.hama.bsp.NullInputFormat;
import org.apache.hama.bsp.TextOutputFormat;
import org.apache.hama.bsp.sync.SyncException;

public class CombineExample {
  private static Path TMP_OUTPUT = new Path("/tmp/combine-"
      + System.currentTimeMillis());

  private static enum CUSTOM_COUNTER {
    CUSTOM_SEND_MESSAGE_COUNTER
  }
  
  public static class MyBSP extends
      BSP<NullWritable, NullWritable, Text, IntWritable, IntWritable> {
    public static final Log LOG = LogFactory.getLog(MyBSP.class);

    @Override
    public void bsp(
        BSPPeer<NullWritable, NullWritable, Text, IntWritable, IntWritable> peer)
        throws IOException, SyncException, InterruptedException {
      for (String peerName : peer.getAllPeerNames()) {
        peer.send(peerName, new IntWritable(1));
        peer.send(peerName, new IntWritable(2));
        peer.send(peerName, new IntWritable(3));
        
        peer.getCounter(CUSTOM_COUNTER.CUSTOM_SEND_MESSAGE_COUNTER).increment(1);
      }
      peer.sync();

      IntWritable received;
      while ((received = peer.getCurrentMessage()) != null) {
        peer.write(new Text("Sum = "), received);
      }
    }

  }

  public static class SumCombiner extends Combiner<IntWritable> {

    @Override
    public IntWritable combine(Iterable<IntWritable> messages) {
      int sum = 0;

      Iterator<IntWritable> it = messages.iterator();
      while (it.hasNext()) {
        sum += it.next().get();
      }

      return new IntWritable(sum);
    }
  }

  static void printOutput(HamaConfiguration conf) throws IOException {
    FileSystem fs = FileSystem.get(conf);
    FileStatus[] files = fs.listStatus(TMP_OUTPUT);
    for (int i = 0; i < files.length; i++) {
      if (files[i].getLen() > 0) {
        FSDataInputStream in = fs.open(files[i].getPath());
        IOUtils.copyBytes(in, System.out, conf, false);
        in.close();
        break;
      }
    }

    fs.delete(TMP_OUTPUT, true);
  }

  public static void main(String[] args) throws InterruptedException,
      IOException, ClassNotFoundException {
    // BSP job configuration
    HamaConfiguration conf = new HamaConfiguration();

    BSPJob bsp = new BSPJob(conf, CombineExample.class);
    // Set the job name
    bsp.setJobName("Combine Example");
    bsp.setBspClass(MyBSP.class);
    bsp.setCombinerClass(SumCombiner.class);
    bsp.setInputFormat(NullInputFormat.class);
    bsp.setOutputKeyClass(Text.class);
    bsp.setOutputValueClass(IntWritable.class);
    bsp.setOutputFormat(TextOutputFormat.class);
    FileOutputFormat.setOutputPath(bsp, TMP_OUTPUT);
    bsp.setNumBspTask(2);

    long startTime = System.currentTimeMillis();
    if (bsp.waitForCompletion(true)) {
      printOutput(conf);
      System.out.println("Job Finished in "
          + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
    }
    
  }
}