src/mapred/org/apache/hadoop/mapred/MapOutputFile.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.hadoop.mapred;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.LocalDirAllocator;
import org.apache.hadoop.fs.Path;

/**
 * Manipulate the working area for the transient store for maps and reduces.
 * 
 * This class is used by map and reduce tasks to identify the directories that
 * they need to write to/read from for intermediate files. The callers of 
 * these methods are from child space and see mapreduce.cluster.local.dir as 
 * taskTracker/jobCache/jobId/attemptId
 * This class should not be used from TaskTracker space.
 */ 
class MapOutputFile {

  private JobConf conf;

  static final String REDUCE_INPUT_FILE_FORMAT_STRING = "%s/map_%d.out";

  MapOutputFile() {
  }

  private LocalDirAllocator lDirAlloc = 
                            new LocalDirAllocator("mapred.local.dir");
  
  /**
   * Return the path to local map output file created earlier
   * 
   * @return path
   * @throws IOException
   */
  public Path getOutputFile()
      throws IOException {
    return lDirAlloc.getLocalPathToRead(TaskTracker.OUTPUT + Path.SEPARATOR
        + "file.out", conf);
  }

  /**
   * Create a local map output file name.
   * 
   * @param size the size of the file
   * @return path
   * @throws IOException
   */
  public Path getOutputFileForWrite(long size)
      throws IOException {
    return lDirAlloc.getLocalPathForWrite(TaskTracker.OUTPUT + Path.SEPARATOR
        + "file.out", size, conf);
  }

  /**
   * Return the path to a local map output index file created earlier
   * 
   * @return path
   * @throws IOException
   */
  public Path getOutputIndexFile()
      throws IOException {
    return lDirAlloc.getLocalPathToRead(TaskTracker.OUTPUT + Path.SEPARATOR
        + "file.out.index", conf);
  }

  /**
   * Create a local map output index file name.
   * 
   * @param size the size of the file
   * @return path
   * @throws IOException
   */
  public Path getOutputIndexFileForWrite(long size)
      throws IOException {
    return lDirAlloc.getLocalPathForWrite(TaskTracker.OUTPUT + Path.SEPARATOR
        + "file.out.index", size, conf);
  }

  /**
   * Return a local map spill file created earlier.
   * 
   * @param spillNumber the number
   * @return path
   * @throws IOException
   */
  public Path getSpillFile(int spillNumber)
      throws IOException {
    return lDirAlloc.getLocalPathToRead(TaskTracker.OUTPUT + "/spill"
        + spillNumber + ".out", conf);
  }

  /**
   * Create a local map spill file name.
   * 
   * @param spillNumber the number
   * @param size the size of the file
   * @return path
   * @throws IOException
   */
  public Path getSpillFileForWrite(int spillNumber, long size)
      throws IOException {
    return lDirAlloc.getLocalPathForWrite(TaskTracker.OUTPUT + "/spill"
        + spillNumber + ".out", size, conf);
  }

  /**
   * Return a local map spill index file created earlier
   * 
   * @param spillNumber the number
   * @return path
   * @throws IOException
   */
  public Path getSpillIndexFile(int spillNumber)
      throws IOException {
    return lDirAlloc.getLocalPathToRead(TaskTracker.OUTPUT + "/spill"
        + spillNumber + ".out.index", conf);
  }

  /**
   * Create a local map spill index file name.
   * 
   * @param spillNumber the number
   * @param size the size of the file
   * @return path
   * @throws IOException
   */
  public Path getSpillIndexFileForWrite(int spillNumber, long size)
      throws IOException {
    return lDirAlloc.getLocalPathForWrite(TaskTracker.OUTPUT + "/spill"
        + spillNumber + ".out.index", size, conf);
  }

  /**
   * Return a local reduce input file created earlier
   * 
   * @param mapId a map task id
   * @return path
   * @throws IOException 
   */
  public Path getInputFile(int mapId)
      throws IOException {
    return lDirAlloc.getLocalPathToRead(String.format(
        REDUCE_INPUT_FILE_FORMAT_STRING, TaskTracker.OUTPUT, Integer
            .valueOf(mapId)), conf);
  }

  /**
   * Create a local reduce input file name.
   * 
   * @param mapId a map task id
   * @param size the size of the file
   * @return path
   * @throws IOException
   */
  public Path getInputFileForWrite(TaskID mapId, long size)
      throws IOException {
    return lDirAlloc.getLocalPathForWrite(String.format(
        REDUCE_INPUT_FILE_FORMAT_STRING, TaskTracker.OUTPUT, mapId.getId()),
        size, conf);
  }

  /** Removes all of the files related to a task. */
  public void removeAll()
      throws IOException {
    conf.deleteLocalFiles(TaskTracker.OUTPUT);
  }

  public void setConf(Configuration conf) {
    if (conf instanceof JobConf) {
      this.conf = (JobConf) conf;
    } else {
      this.conf = new JobConf(conf);
    }
  }
}