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    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import org.apache.hadoop.classification.InterfaceStability;
025    import org.apache.hadoop.mapreduce.JobContext;
026    import org.apache.hadoop.mapreduce.OutputCommitter;
027    import org.apache.hadoop.mapreduce.OutputFormat;
028    import org.apache.hadoop.mapreduce.RecordWriter;
029    import org.apache.hadoop.mapreduce.TaskAttemptContext;
030    
031    /**
032     * Consume all outputs and put them in /dev/null. 
033     */
034    @InterfaceAudience.Public
035    @InterfaceStability.Stable
036    public class NullOutputFormat<K, V> extends OutputFormat<K, V> {
037      
038      @Override
039      public RecordWriter<K, V> 
040             getRecordWriter(TaskAttemptContext context) {
041        return new RecordWriter<K, V>(){
042            public void write(K key, V value) { }
043            public void close(TaskAttemptContext context) { }
044          };
045      }
046      
047      @Override
048      public void checkOutputSpecs(JobContext context) { }
049      
050      @Override
051      public OutputCommitter getOutputCommitter(TaskAttemptContext context) {
052        return new OutputCommitter() {
053          public void abortTask(TaskAttemptContext taskContext) { }
054          public void cleanupJob(JobContext jobContext) { }
055          public void commitTask(TaskAttemptContext taskContext) { }
056          public boolean needsTaskCommit(TaskAttemptContext taskContext) {
057            return false;
058          }
059          public void setupJob(JobContext jobContext) { }
060          public void setupTask(TaskAttemptContext taskContext) { }
061    
062          @Override
063          public boolean isRecoverySupported() {
064            return true;
065          }
066    
067          @Override
068          public void recoverTask(TaskAttemptContext taskContext)
069              throws IOException {
070            // Nothing to do for recovering the task.
071          }
072        };
073      }
074    }