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.lib;
020    
021    import java.io.IOException;
022    import java.util.List;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.classification.InterfaceStability;
026    import org.apache.hadoop.fs.FileStatus;
027    import org.apache.hadoop.fs.FileSystem;
028    import org.apache.hadoop.fs.Path;
029    import org.apache.hadoop.fs.PathFilter;
030    import org.apache.hadoop.io.compress.CompressionCodec;
031    import org.apache.hadoop.io.compress.CompressionCodecFactory;
032    import org.apache.hadoop.io.compress.SplittableCompressionCodec;
033    import org.apache.hadoop.mapred.InputFormat;
034    import org.apache.hadoop.mapred.InputSplit;
035    import org.apache.hadoop.mapred.JobConf;
036    import org.apache.hadoop.mapred.RecordReader;
037    import org.apache.hadoop.mapred.Reporter;
038    import org.apache.hadoop.mapreduce.Job;
039    import org.apache.hadoop.mapreduce.JobContext;
040    import 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
063    public 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(new Job(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(new Job(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    }