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
019 package org.apache.hadoop.mapred;
020
021 import java.io.IOException;
022
023 import org.apache.hadoop.fs.FileSystem;
024 import org.apache.hadoop.fs.Path;
025
026 import org.apache.hadoop.io.MapFile;
027 import org.apache.hadoop.io.WritableComparable;
028 import org.apache.hadoop.io.Writable;
029 import org.apache.hadoop.io.SequenceFile.CompressionType;
030 import org.apache.hadoop.io.compress.CompressionCodec;
031 import org.apache.hadoop.io.compress.DefaultCodec;
032 import org.apache.hadoop.classification.InterfaceAudience;
033 import org.apache.hadoop.classification.InterfaceStability;
034 import org.apache.hadoop.conf.Configuration;
035 import org.apache.hadoop.util.Progressable;
036 import org.apache.hadoop.util.ReflectionUtils;
037
038 /** An {@link OutputFormat} that writes {@link MapFile}s.
039 */
040 @InterfaceAudience.Public
041 @InterfaceStability.Stable
042 public class MapFileOutputFormat
043 extends 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