edu.stolaf.cs.wmrserver.streaming.PipeReducer.java Source code

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Here is the source code for edu.stolaf.cs.wmrserver.streaming.PipeReducer.java

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/**
 * 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.
 * 
 * Modified by the WebMapReduce developers.
 */

package edu.stolaf.cs.wmrserver.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.util.StringUtils;

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.
        return (argv != null);
    }

    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("mapred.skip.on", 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:"
                                + StringUtils.stringifyException(outerrThreadsThrowable));
                    }
                    write(key);
                    clientOut_.write(getInputSeparator());
                    write(val);
                    clientOut_.write('\n');
                } 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";
            }
            ;
            appendLogToJobLog("failure");
            mapRedFinished();
            throw new IOException(extraInfo + getContext() + io.getMessage());
        }
    }

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

    byte[] getInputSeparator() {
        return reduceInputFieldSeparator;
    }

    @Override
    byte[] getFieldSeparator() {
        return reduceOutFieldSeparator;
    }

    @Override
    int getNumOfKeyFields() {
        return numOfReduceOutputKeyFields;
    }

}