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.lib;
020
021import java.io.IOException;
022import java.util.List;
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026import org.apache.hadoop.fs.FileStatus;
027import org.apache.hadoop.fs.FileSystem;
028import org.apache.hadoop.fs.Path;
029import org.apache.hadoop.fs.PathFilter;
030import org.apache.hadoop.io.compress.CompressionCodec;
031import org.apache.hadoop.io.compress.CompressionCodecFactory;
032import org.apache.hadoop.io.compress.SplittableCompressionCodec;
033import org.apache.hadoop.mapred.InputFormat;
034import org.apache.hadoop.mapred.InputSplit;
035import org.apache.hadoop.mapred.JobConf;
036import org.apache.hadoop.mapred.RecordReader;
037import org.apache.hadoop.mapred.Reporter;
038import org.apache.hadoop.mapreduce.Job;
039import org.apache.hadoop.mapreduce.JobContext;
040import org.apache.hadoop.mapreduce.TaskAttemptContext;
041
042/**
043 * An abstract {@link org.apache.hadoop.mapred.InputFormat} that returns {@link CombineFileSplit}'s
044 * in {@link org.apache.hadoop.mapred.InputFormat#getSplits(JobConf, int)} method. 
045 * Splits are constructed from the files under the input paths. 
046 * A split cannot have files from different pools.
047 * Each split returned may contain blocks from different files.
048 * If a maxSplitSize is specified, then blocks on the same node are
049 * combined to form a single split. Blocks that are left over are
050 * then combined with other blocks in the same rack. 
051 * If maxSplitSize is not specified, then blocks from the same rack
052 * are combined in a single split; no attempt is made to create
053 * node-local splits.
054 * If the maxSplitSize is equal to the block size, then this class
055 * is similar to the default spliting behaviour in Hadoop: each
056 * block is a locally processed split.
057 * Subclasses implement {@link org.apache.hadoop.mapred.InputFormat#getRecordReader(InputSplit, JobConf, Reporter)}
058 * to construct <code>RecordReader</code>'s for <code>CombineFileSplit</code>'s.
059 * @see CombineFileSplit
060 */
061@InterfaceAudience.Public
062@InterfaceStability.Stable
063public abstract class CombineFileInputFormat<K, V>
064  extends org.apache.hadoop.mapreduce.lib.input.CombineFileInputFormat<K, V> 
065  implements InputFormat<K, V>{
066
067  /**
068   * default constructor
069   */
070  public CombineFileInputFormat() {
071  }
072
073  public InputSplit[] getSplits(JobConf job, int numSplits) 
074    throws IOException {
075    List<org.apache.hadoop.mapreduce.InputSplit> newStyleSplits =
076      super.getSplits(Job.getInstance(job));
077    InputSplit[] ret = new InputSplit[newStyleSplits.size()];
078    for(int pos = 0; pos < newStyleSplits.size(); ++pos) {
079      org.apache.hadoop.mapreduce.lib.input.CombineFileSplit newStyleSplit = 
080        (org.apache.hadoop.mapreduce.lib.input.CombineFileSplit) newStyleSplits.get(pos);
081      ret[pos] = new CombineFileSplit(job, newStyleSplit.getPaths(),
082        newStyleSplit.getStartOffsets(), newStyleSplit.getLengths(),
083        newStyleSplit.getLocations());
084    }
085    return ret;
086  }
087  
088  /**
089   * Create a new pool and add the filters to it.
090   * A split cannot have files from different pools.
091   * @deprecated Use {@link #createPool(List)}.
092   */
093  @Deprecated
094  protected void createPool(JobConf conf, List<PathFilter> filters) {
095    createPool(filters);
096  }
097
098  /**
099   * Create a new pool and add the filters to it. 
100   * A pathname can satisfy any one of the specified filters.
101   * A split cannot have files from different pools.
102   * @deprecated Use {@link #createPool(PathFilter...)}.
103   */
104  @Deprecated
105  protected void createPool(JobConf conf, PathFilter... filters) {
106    createPool(filters);
107  }
108
109  /**
110   * This is not implemented yet. 
111   */
112  public abstract RecordReader<K, V> getRecordReader(InputSplit split,
113                                      JobConf job, Reporter reporter)
114    throws IOException;
115
116  // abstract method from super class implemented to return null
117  public org.apache.hadoop.mapreduce.RecordReader<K, V> createRecordReader(
118      org.apache.hadoop.mapreduce.InputSplit split,
119      TaskAttemptContext context) throws IOException {
120    return null;
121  }
122  
123  /** List input directories.
124   * Subclasses may override to, e.g., select only files matching a regular
125   * expression. 
126   * 
127   * @param job the job to list input paths for
128   * @return array of FileStatus objects
129   * @throws IOException if zero items.
130   */
131  protected FileStatus[] listStatus(JobConf job) throws IOException {
132    List<FileStatus> result = super.listStatus(Job.getInstance(job));
133    return result.toArray(new FileStatus[result.size()]);
134  }
135
136  /**
137   * Subclasses should avoid overriding this method and should instead only
138   * override {@link #isSplitable(FileSystem, Path)}.  The implementation of
139   * this method simply calls the other method to preserve compatibility.
140   * @see <a href="https://issues.apache.org/jira/browse/MAPREDUCE-5530">
141   * MAPREDUCE-5530</a>
142   *
143   * @param context the job context
144   * @param file the file name to check
145   * @return is this file splitable?
146   */
147  @InterfaceAudience.Private
148  @Override
149  protected boolean isSplitable(JobContext context, Path file) {
150    try {
151      return isSplitable(FileSystem.get(context.getConfiguration()), file);
152    }
153    catch (IOException ioe) {
154      throw new RuntimeException(ioe);
155    }
156  }
157
158  protected boolean isSplitable(FileSystem fs, Path file) {
159    final CompressionCodec codec =
160      new CompressionCodecFactory(fs.getConf()).getCodec(file);
161    if (null == codec) {
162      return true;
163    }
164    return codec instanceof SplittableCompressionCodec;
165  }
166}