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.mapreduce.lib.output;
020
021 import java.io.IOException;
022 import java.util.Arrays;
023
024 import org.apache.hadoop.fs.FileSystem;
025 import org.apache.hadoop.fs.Path;
026 import org.apache.hadoop.fs.FileUtil;
027
028 import org.apache.hadoop.io.MapFile;
029 import org.apache.hadoop.io.WritableComparable;
030 import org.apache.hadoop.io.Writable;
031 import org.apache.hadoop.io.SequenceFile.CompressionType;
032 import org.apache.hadoop.io.compress.CompressionCodec;
033 import org.apache.hadoop.io.compress.DefaultCodec;
034 import org.apache.hadoop.mapreduce.Partitioner;
035 import org.apache.hadoop.mapreduce.RecordWriter;
036 import org.apache.hadoop.mapreduce.TaskAttemptContext;
037 import org.apache.hadoop.util.ReflectionUtils;
038 import org.apache.hadoop.classification.InterfaceAudience;
039 import org.apache.hadoop.classification.InterfaceStability;
040 import org.apache.hadoop.conf.Configuration;
041
042 /**
043 * An {@link org.apache.hadoop.mapreduce.OutputFormat} that writes
044 * {@link MapFile}s.
045 */
046 @InterfaceAudience.Public
047 @InterfaceStability.Stable
048 public class MapFileOutputFormat
049 extends FileOutputFormat<WritableComparable<?>, Writable> {
050
051 public RecordWriter<WritableComparable<?>, Writable> getRecordWriter(
052 TaskAttemptContext context) throws IOException {
053 Configuration conf = context.getConfiguration();
054 CompressionCodec codec = null;
055 CompressionType compressionType = CompressionType.NONE;
056 if (getCompressOutput(context)) {
057 // find the kind of compression to do
058 compressionType = SequenceFileOutputFormat.getOutputCompressionType(context);
059
060 // find the right codec
061 Class<?> codecClass = getOutputCompressorClass(context,
062 DefaultCodec.class);
063 codec = (CompressionCodec) ReflectionUtils.newInstance(codecClass, conf);
064 }
065
066 Path file = getDefaultWorkFile(context, "");
067 FileSystem fs = file.getFileSystem(conf);
068 // ignore the progress parameter, since MapFile is local
069 final MapFile.Writer out =
070 new MapFile.Writer(conf, fs, file.toString(),
071 context.getOutputKeyClass().asSubclass(WritableComparable.class),
072 context.getOutputValueClass().asSubclass(Writable.class),
073 compressionType, codec, context);
074
075 return new RecordWriter<WritableComparable<?>, Writable>() {
076 public void write(WritableComparable<?> key, Writable value)
077 throws IOException {
078 out.append(key, value);
079 }
080
081 public void close(TaskAttemptContext context) throws IOException {
082 out.close();
083 }
084 };
085 }
086
087 /** Open the output generated by this format. */
088 public static MapFile.Reader[] getReaders(Path dir,
089 Configuration conf) throws IOException {
090 FileSystem fs = dir.getFileSystem(conf);
091 Path[] names = FileUtil.stat2Paths(fs.listStatus(dir));
092
093 // sort names, so that hash partitioning works
094 Arrays.sort(names);
095
096 MapFile.Reader[] parts = new MapFile.Reader[names.length];
097 for (int i = 0; i < names.length; i++) {
098 parts[i] = new MapFile.Reader(fs, names[i].toString(), conf);
099 }
100 return parts;
101 }
102
103 /** Get an entry from output generated by this class. */
104 public static <K extends WritableComparable<?>, V extends Writable>
105 Writable getEntry(MapFile.Reader[] readers,
106 Partitioner<K, V> partitioner, K key, V value) throws IOException {
107 int part = partitioner.getPartition(key, value, readers.length);
108 return readers[part].get(key, value);
109 }
110 }
111