hadoop PipeReducer 源码

haddop PipeReducer 代码

文件路径：/hadoop-tools/hadoop-streaming/src/main/java/org/apache/hadoop/streaming/PipeReducer.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.streaming;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Iterator;
import java.net.URLDecoder;

import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.SkipBadRecords;
import org.apache.hadoop.mapreduce.MRJobConfig;
import org.apache.hadoop.streaming.io.InputWriter;
import org.apache.hadoop.streaming.io.OutputReader;

import org.apache.hadoop.io.Writable;

/** A generic Reducer bridge.
 *  It delegates operations to an external program via stdin and stdout.
 */
public class PipeReducer extends PipeMapRed implements Reducer {

  private byte[] reduceOutFieldSeparator;
  private byte[] reduceInputFieldSeparator;
  private int numOfReduceOutputKeyFields = 1;
  private boolean skipping = false;
  
  String getPipeCommand(JobConf job) {
    String str = job.get("stream.reduce.streamprocessor");
    if (str == null) {
      return str;
    }
    try {
      return URLDecoder.decode(str, "UTF-8");
    } catch (UnsupportedEncodingException e) {
      System.err.println("stream.reduce.streamprocessor in jobconf not found");
      return null;
    }
  }

  boolean getDoPipe() {
    String argv = getPipeCommand(job_);
    // Currently: null is identity reduce. REDUCE_NONE is no-map-outputs.
    return (argv != null) && !StreamJob.REDUCE_NONE.equals(argv);
  }

  public void configure(JobConf job) {
    super.configure(job);
    //disable the auto increment of the counter. For streaming, no of 
    //processed records could be different(equal or less) than the no of 
    //records input.
    SkipBadRecords.setAutoIncrReducerProcCount(job, false);
    skipping = job.getBoolean(MRJobConfig.SKIP_RECORDS, false);

    try {
      reduceOutFieldSeparator = job_.get("stream.reduce.output.field.separator", "\t").getBytes("UTF-8");
      reduceInputFieldSeparator = job_.get("stream.reduce.input.field.separator", "\t").getBytes("UTF-8");
      this.numOfReduceOutputKeyFields = job_.getInt("stream.num.reduce.output.key.fields", 1);
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException("The current system does not support UTF-8 encoding!", e);
    }
  }

  public void reduce(Object key, Iterator values, OutputCollector output,
                     Reporter reporter) throws IOException {

    // init
    if (doPipe_ && outThread_ == null) {
      startOutputThreads(output, reporter);
    }
    try {
      while (values.hasNext()) {
        Writable val = (Writable) values.next();
        numRecRead_++;
        maybeLogRecord();
        if (doPipe_) {
          if (outerrThreadsThrowable != null) {
            mapRedFinished();
            throw new IOException("MROutput/MRErrThread failed:",
                outerrThreadsThrowable);
          }
          inWriter_.writeKey(key);
          inWriter_.writeValue(val);
        } else {
          // "identity reduce"
          output.collect(key, val);
        }
      }
      if(doPipe_ && skipping) {
        //flush the streams on every record input if running in skip mode
        //so that we don't buffer other records surrounding a bad record. 
        clientOut_.flush();
      }
    } catch (IOException io) {
      // a common reason to get here is failure of the subprocess.
      // Document that fact, if possible.
      String extraInfo = "";
      try {
        int exitVal = sim.exitValue();
	if (exitVal == 0) {
	  extraInfo = "subprocess exited successfully\n";
	} else {
	  extraInfo = "subprocess exited with error code " + exitVal + "\n";
	};
      } catch (IllegalThreadStateException e) {
        // hmm, but child is still running.  go figure.
	extraInfo = "subprocess still running\n";
      };
      mapRedFinished();
      throw new IOException(extraInfo + getContext() + io.getMessage());
    }
  }

  public void close() {
    mapRedFinished();
  }

  @Override
  public byte[] getInputSeparator() {
    return reduceInputFieldSeparator;
  }

  @Override
  public byte[] getFieldSeparator() {
    return reduceOutFieldSeparator;
  }
  
  @Override
  public int getNumOfKeyFields() {
    return numOfReduceOutputKeyFields;
  }
  
  @Override
  InputWriter createInputWriter() throws IOException {
    return super.createInputWriter(reduceInputWriterClass_);
  }

  @Override
  OutputReader createOutputReader() throws IOException {
    return super.createOutputReader(reduceOutputReaderClass_);
  }

}

相关信息

hadoop 源码目录

相关文章

hadoop AutoInputFormat 源码

hadoop DumpTypedBytes 源码

hadoop Environment 源码

hadoop HadoopStreaming 源码

hadoop JarBuilder 源码

hadoop LoadTypedBytes 源码

hadoop PathFinder 源码

hadoop PipeCombiner 源码

hadoop PipeMapRed 源码

hadoop PipeMapRunner 源码