hadoop MultiFileInputFormat 源码

  • 2022-10-20
  • 浏览 (159)

haddop MultiFileInputFormat 代码

文件路径:/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MultiFileInputFormat.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.mapred;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.FileUtil;
import org.apache.hadoop.fs.Path;

/**
 * An abstract {@link InputFormat} that returns {@link MultiFileSplit}'s
 * in {@link #getSplits(JobConf, int)} method. Splits are constructed from 
 * the files under the input paths. Each split returned contains <i>nearly</i>
 * equal content length. <br>  
 * Subclasses implement {@link #getRecordReader(InputSplit, JobConf, Reporter)}
 * to construct <code>RecordReader</code>'s for <code>MultiFileSplit</code>'s.
 * @see MultiFileSplit
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public abstract class MultiFileInputFormat<K, V>
  extends FileInputFormat<K, V> {

  @Override
  public InputSplit[] getSplits(JobConf job, int numSplits) 
    throws IOException {
    
    Path[] paths = FileUtil.stat2Paths(listStatus(job));
    List<MultiFileSplit> splits = new ArrayList<MultiFileSplit>(Math.min(numSplits, paths.length));
    if (paths.length != 0) {
      // HADOOP-1818: Manage splits only if there are paths
      long[] lengths = new long[paths.length];
      long totLength = 0;
      for(int i=0; i<paths.length; i++) {
        FileSystem fs = paths[i].getFileSystem(job);
        lengths[i] = fs.getContentSummary(paths[i]).getLength();
        totLength += lengths[i];
      }
      double avgLengthPerSplit = ((double)totLength) / numSplits;
      long cumulativeLength = 0;

      int startIndex = 0;

      for(int i=0; i<numSplits; i++) {
        int splitSize = findSize(i, avgLengthPerSplit, cumulativeLength
            , startIndex, lengths);
        if (splitSize != 0) {
          // HADOOP-1818: Manage split only if split size is not equals to 0
          Path[] splitPaths = new Path[splitSize];
          long[] splitLengths = new long[splitSize];
          System.arraycopy(paths, startIndex, splitPaths , 0, splitSize);
          System.arraycopy(lengths, startIndex, splitLengths , 0, splitSize);
          splits.add(new MultiFileSplit(job, splitPaths, splitLengths));
          startIndex += splitSize;
          for(long l: splitLengths) {
            cumulativeLength += l;
          }
        }
      }
    }
    return splits.toArray(new MultiFileSplit[splits.size()]);    
  }

  private int findSize(int splitIndex, double avgLengthPerSplit
      , long cumulativeLength , int startIndex, long[] lengths) {
    
    if(splitIndex == lengths.length - 1)
      return lengths.length - startIndex;
    
    long goalLength = (long)((splitIndex + 1) * avgLengthPerSplit);
    long partialLength = 0;
    // accumulate till just above the goal length;
    for(int i = startIndex; i < lengths.length; i++) {
      partialLength += lengths[i];
      if(partialLength + cumulativeLength >= goalLength) {
        return i - startIndex + 1;
      }
    }
    return lengths.length - startIndex;
  }
  
  @Override
  public abstract RecordReader<K, V> getRecordReader(InputSplit split,
      JobConf job, Reporter reporter)
      throws IOException;
}

相关信息

hadoop 源码目录

相关文章

hadoop AMFeedback 源码

hadoop BackupStore 源码

hadoop BasicTypeSorterBase 源码

hadoop BufferSorter 源码

hadoop CleanupQueue 源码

hadoop Clock 源码

hadoop ClusterStatus 源码

hadoop Counters 源码

hadoop CumulativePeriodicStats 源码

hadoop DeprecatedQueueConfigurationParser 源码

0  赞