001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapred;
020
021import java.io.IOException;
022
023import org.apache.hadoop.fs.FileSystem;
024import org.apache.hadoop.fs.Path;
025
026import org.apache.hadoop.io.MapFile;
027import org.apache.hadoop.io.WritableComparable;
028import org.apache.hadoop.io.Writable;
029import org.apache.hadoop.io.SequenceFile.CompressionType;
030import org.apache.hadoop.io.compress.CompressionCodec;
031import org.apache.hadoop.io.compress.DefaultCodec;
032import org.apache.hadoop.classification.InterfaceAudience;
033import org.apache.hadoop.classification.InterfaceStability;
034import org.apache.hadoop.conf.Configuration;
035import org.apache.hadoop.util.Progressable;
036import org.apache.hadoop.util.ReflectionUtils;
037
038/** An {@link OutputFormat} that writes {@link MapFile}s.
039 */
040@InterfaceAudience.Public
041@InterfaceStability.Stable
042public class MapFileOutputFormat 
043extends FileOutputFormat<WritableComparable, Writable> {
044
045  public RecordWriter<WritableComparable, Writable> getRecordWriter(FileSystem ignored, JobConf job,
046                                      String name, Progressable progress)
047    throws IOException {
048    // get the path of the temporary output file 
049    Path file = FileOutputFormat.getTaskOutputPath(job, name);
050    
051    FileSystem fs = file.getFileSystem(job);
052    CompressionCodec codec = null;
053    CompressionType compressionType = CompressionType.NONE;
054    if (getCompressOutput(job)) {
055      // find the kind of compression to do
056      compressionType = SequenceFileOutputFormat.getOutputCompressionType(job);
057
058      // find the right codec
059      Class<? extends CompressionCodec> codecClass = getOutputCompressorClass(job,
060          DefaultCodec.class);
061      codec = ReflectionUtils.newInstance(codecClass, job);
062    }
063    
064    // ignore the progress parameter, since MapFile is local
065    final MapFile.Writer out =
066      new MapFile.Writer(job, fs, file.toString(),
067                         job.getOutputKeyClass().asSubclass(WritableComparable.class),
068                         job.getOutputValueClass().asSubclass(Writable.class),
069                         compressionType, codec,
070                         progress);
071
072    return new RecordWriter<WritableComparable, Writable>() {
073
074        public void write(WritableComparable key, Writable value)
075          throws IOException {
076
077          out.append(key, value);
078        }
079
080        public void close(Reporter reporter) throws IOException { out.close();}
081      };
082  }
083
084  /** Open the output generated by this format. */
085  public static MapFile.Reader[] getReaders(FileSystem ignored, Path dir,
086                                            Configuration conf)
087      throws IOException {
088    return org.apache.hadoop.mapreduce.lib.output.MapFileOutputFormat.
089      getReaders(dir, conf);
090  }
091    
092  /** Get an entry from output generated by this class. */
093  public static <K extends WritableComparable, V extends Writable>
094  Writable getEntry(MapFile.Reader[] readers,
095                                  Partitioner<K, V> partitioner,
096                                  K key,
097                                  V value) throws IOException {
098    int part = partitioner.getPartition(key, value, readers.length);
099    return readers[part].get(key, value);
100  }
101
102}
103