pipemapper.java

hadoop:Nutch集群平台

/**
 * Copyright 2006 The Apache Software Foundation
 *
 * Licensed 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.*;

import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.OutputCollector;

import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.Writable;

/** A generic Mapper bridge.
 *  It delegates operations to an external program via stdin and stdout.
 *  @author Michel Tourn
 */
public class PipeMapper extends PipeMapRed implements Mapper {

  String getPipeCommand(JobConf job) {
    return job.get("stream.map.streamprocessor");
  }

  String getKeyColPropName() {
    return "mapKeyCols";
  }

  boolean getUseSideEffect() {
    return StreamUtil.getUseMapSideEffect(job_);
  }

  boolean getDoPipe() {
    return true;
  }

  // Do NOT declare default constructor
  // (MapRed creates it reflectively)

  public void map(WritableComparable key, Writable value, OutputCollector output, Reporter reporter) throws IOException {
    // init
    if (outThread_ == null) {
      startOutputThreads(output, reporter);
    }
    try {
      // 1/4 Hadoop in
      numRecRead_++;
      maybeLogRecord();
      if (debugFailDuring_ && numRecRead_ == 3) {
        throw new IOException("debugFailDuring_");
      }

      // 2/4 Hadoop to Tool
      if (numExceptions_ == 0) {
        if (optUseKey_) {
          write(key);
          clientOut_.write('\t');
        }
        write(value);
        clientOut_.write('\n');
        clientOut_.flush();
      } else {
        numRecSkipped_++;
      }
    } catch (IOException io) {
      numExceptions_++;
      if (numExceptions_ > 1 || numRecWritten_ < minRecWrittenToEnableSkip_) {
        // terminate with failure
        String msg = logFailure(io);
        appendLogToJobLog("failure");
        mapRedFinished();
        throw new IOException(msg);
      } else {
        // terminate with success:
        // swallow input records although the stream processor failed/closed
      }
    }
  }

  public void close() {
    appendLogToJobLog("success");
    mapRedFinished();
  }

}