org.apache.hama.bsp.message.io.CombineSpilledDataProcessor.java Source code

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Here is the source code for org.apache.hama.bsp.message.io.CombineSpilledDataProcessor.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.
 */
package org.apache.hama.bsp.message.io;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.ByteBuffer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Writable;
import org.apache.hama.Constants;
import org.apache.hama.bsp.Combiner;
import org.apache.hama.util.ReflectionUtils;

/**
 * This data processor adds a stage in between the spillage of data. Based on
 * the combiner provided it combines the bunch of messages in the byte buffer
 * and then writes them to the file writer using the base class handle method.
 * TODO: Experiment the feature with pipelining design.
 */
public class CombineSpilledDataProcessor<M extends Writable> extends WriteSpilledDataProcessor {

    public static Log LOG = LogFactory.getLog(CombineSpilledDataProcessor.class);

    Combiner<M> combiner;
    M writableObject;
    ReusableByteBuffer<M> iterator;
    DirectByteBufferOutputStream combineOutputBuffer;
    ByteBuffer combineBuffer;

    public CombineSpilledDataProcessor(String fileName) throws FileNotFoundException {
        super(fileName);
    }

    @Override
    public boolean init(Configuration conf) {
        if (!super.init(conf)) {
            return false;
        }
        String className = conf.get(Constants.COMBINER_CLASS);

        if (className == null)
            return true;
        try {
            combiner = ReflectionUtils.newInstance(className);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
        className = conf.get(Constants.MESSAGE_CLASS);

        if (className != null) {
            try {
                writableObject = ReflectionUtils.newInstance(className);
                iterator = new ReusableByteBuffer<M>(writableObject);
            } catch (ClassNotFoundException e) {
                LOG.error("Error combining the records.", e);
                return false;
            }
        }

        combineOutputBuffer = new DirectByteBufferOutputStream();
        combineBuffer = ByteBuffer.allocateDirect(Constants.BUFFER_DEFAULT_SIZE);
        combineOutputBuffer.setBuffer(combineBuffer);
        return true;
    }

    @Override
    public boolean handleSpilledBuffer(SpilledByteBuffer buffer) {

        if (combiner == null || writableObject == null) {
            return super.handleSpilledBuffer(buffer);
        }

        try {
            iterator.set(buffer);
        } catch (IOException e1) {
            LOG.error("Error setting buffer for combining data", e1);
            return false;
        }
        Writable combinedMessage = combiner.combine(iterator);
        try {
            iterator.prepareForNext();
        } catch (IOException e1) {
            LOG.error("Error preparing for next buffer.", e1);
            return false;
        }
        try {
            combinedMessage.write(this.combineOutputBuffer);
        } catch (IOException e) {
            LOG.error("Error writing the combiner output.", e);
            return false;
        }
        try {
            this.combineOutputBuffer.flush();
        } catch (IOException e) {
            LOG.error("Error flushing the combiner output.", e);
            return false;
        }
        this.combineOutputBuffer.getBuffer().flip();
        try {
            return super.handleSpilledBuffer(new SpilledByteBuffer(this.combineOutputBuffer.getBuffer(),
                    this.combineOutputBuffer.getBuffer().remaining()));
        } finally {
            this.combineOutputBuffer.clear();
        }
    }

    @Override
    public boolean close() {
        return true;
    }

}