hadoop LazyOutputFormat 源码

haddop LazyOutputFormat 代码

文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/output/LazyOutputFormat.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.hadoop.mapreduce.lib.output;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.JobContext;
import org.apache.hadoop.mapreduce.OutputCommitter;
import org.apache.hadoop.mapreduce.OutputFormat;
import org.apache.hadoop.mapreduce.RecordWriter;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.util.ReflectionUtils;

/**
 * A Convenience class that creates output lazily.
 * Use in conjuction with org.apache.hadoop.mapreduce.lib.output.MultipleOutputs to recreate the
 * behaviour of org.apache.hadoop.mapred.lib.MultipleTextOutputFormat (etc) of the old Hadoop API.
 * See {@link MultipleOutputs} documentation for more information.
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class LazyOutputFormat <K,V> extends FilterOutputFormat<K, V> {
  public static String OUTPUT_FORMAT = 
    "mapreduce.output.lazyoutputformat.outputformat";
  /**
   * Set the underlying output format for LazyOutputFormat.
   * @param job the {@link Job} to modify
   * @param theClass the underlying class
   */
  @SuppressWarnings("unchecked")
  public static void  setOutputFormatClass(Job job, 
                                     Class<? extends OutputFormat> theClass) {
      job.setOutputFormatClass(LazyOutputFormat.class);
      job.getConfiguration().setClass(OUTPUT_FORMAT, 
          theClass, OutputFormat.class);
  }

  @SuppressWarnings("unchecked")
  private void getBaseOutputFormat(Configuration conf) 
  throws IOException {
    baseOut =  ((OutputFormat<K, V>) ReflectionUtils.newInstance(
      conf.getClass(OUTPUT_FORMAT, null), conf));
    if (baseOut == null) {
      throw new IOException("Output Format not set for LazyOutputFormat");
    }
  }

  @Override
  public RecordWriter<K, V> getRecordWriter(TaskAttemptContext context)
  throws IOException, InterruptedException {
    if (baseOut == null) {
      getBaseOutputFormat(context.getConfiguration());
    }
    return new LazyRecordWriter<K, V>(baseOut, context);
  }
  
  @Override
  public void checkOutputSpecs(JobContext context) 
  throws IOException, InterruptedException {
    if (baseOut == null) {
      getBaseOutputFormat(context.getConfiguration());
    }
   super.checkOutputSpecs(context);
  }
  
  @Override
  public OutputCommitter getOutputCommitter(TaskAttemptContext context) 
  throws IOException, InterruptedException {
    if (baseOut == null) {
      getBaseOutputFormat(context.getConfiguration());
    }
    return super.getOutputCommitter(context);
  }
  
  /**
   * A convenience class to be used with LazyOutputFormat
   */
  private static class LazyRecordWriter<K,V> extends FilterRecordWriter<K,V> {

    final OutputFormat<K,V> outputFormat;
    final TaskAttemptContext taskContext;

    public LazyRecordWriter(OutputFormat<K,V> out, 
                            TaskAttemptContext taskContext)
    throws IOException, InterruptedException {
      this.outputFormat = out;
      this.taskContext = taskContext;
    }

    @Override
    public void write(K key, V value) throws IOException, InterruptedException {
      if (rawWriter == null) {
        rawWriter = outputFormat.getRecordWriter(taskContext);
      }
      rawWriter.write(key, value);
    }

    @Override
    public void close(TaskAttemptContext context) 
    throws IOException, InterruptedException {
      if (rawWriter != null) {
        rawWriter.close(context);
      }
    }

  }
}

相关信息

hadoop 源码目录

相关文章

hadoop BindingPathOutputCommitter 源码

hadoop FileOutputCommitter 源码

hadoop FileOutputCommitterFactory 源码

hadoop FileOutputFormat 源码

hadoop FileOutputFormatCounter 源码

hadoop FilterOutputFormat 源码

hadoop MapFileOutputFormat 源码

hadoop MultipleOutputs 源码

hadoop NamedCommitterFactory 源码

hadoop NullOutputFormat 源码