SWMapEntryPoint.java

/*
 * Copyright (c) 2010 Chris Smowton <chris.smowton@cl.cam.ac.uk>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

package uk.co.mrry.mercator.mapreduce;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.lang.reflect.Constructor;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.io.serializer.Deserializer;
import org.apache.hadoop.io.serializer.SerializationFactory;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.Partitioner;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.StatusReporter;
import org.apache.hadoop.util.Progress;
import org.apache.hadoop.util.ReflectionUtils;

import uk.co.mrry.mercator.task.Task;

public class SWMapEntryPoint implements Task {

  @SuppressWarnings("unchecked")
  @Override
  public void invoke(FileInputStream[] fis, FileOutputStream[] fos, String[] args) {
    // This method is used to kick off a Hadoop Mapreduce job running on Skywriting
    
    /* We assume that args supplies the necessary class names in the following form:
     * 1) Mapper class name
     * 2) Reducer class name
     * 3) Partitioner class name
     * 4) Input record reader class name
     */
    if(args.length < 4) 
      System.out.println("[Skywriting] Insufficient arguments passed to SWMapEntryPoint");
    
    String mapperClassName = args[0];
    String reducerClassName = args[1];
    String partitionerClassName = args[2];
    String inputRecordReaderClassName = args[3];
    
    try {
      // make a mapper
      Mapper mapper = (Mapper)ReflectionUtils.newInstance(Class.forName(mapperClassName), null);
      
      // make a partitioner
      Partitioner partitioner = (Partitioner)ReflectionUtils.newInstance(Class.forName(partitionerClassName), null);
      
      // TODO make this use reflection and the 4th argument
      SWLineRecordReader input = new SWLineRecordReader();
  
      // Make a fake split - TODO check indexing here
      SWInputSplit split = new SWInputSplit(fis[0]);
  
      Mapper.Context mapperContext = null;
      Constructor<Mapper.Context> contextConstructor =
        Mapper.Context.class.getConstructor
        (new Class[]{Mapper.class,
            Configuration.class,
            org.apache.hadoop.mapreduce.TaskAttemptID.class,
            RecordReader.class,
            RecordWriter.class,
            OutputCommitter.class,
            StatusReporter.class,
            SWInputSplit.class});

      // get an output object
      SWMapperOutputCollector output = null;
      output = new SWMapperOutputCollector(partitioner, fos);

      // Create a mapper (task) context
      mapperContext = contextConstructor.newInstance(mapper, null, null,
          input, output, null, null, null);

      input.initialize(split, mapperContext);
      mapper.run(mapperContext);
      input.close();
      output.close(mapperContext);
      
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
    
  }

}