org.apache.hadoop.mapred.FadvisedFileRegion.java Source code

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Here is the source code for org.apache.hadoop.mapred.FadvisedFileRegion.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.hadoop.mapred;

import java.io.FileDescriptor;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.WritableByteChannel;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.io.ReadaheadPool;
import org.apache.hadoop.io.ReadaheadPool.ReadaheadRequest;
import org.apache.hadoop.io.nativeio.NativeIO;

import static org.apache.hadoop.io.nativeio.NativeIO.POSIX.POSIX_FADV_DONTNEED;

import org.jboss.netty.channel.DefaultFileRegion;

import com.google.common.annotations.VisibleForTesting;

public class FadvisedFileRegion extends DefaultFileRegion {

    private static final Log LOG = LogFactory.getLog(FadvisedFileRegion.class);

    private final boolean manageOsCache;
    private final int readaheadLength;
    private final ReadaheadPool readaheadPool;
    private final FileDescriptor fd;
    private final String identifier;
    private final long count;
    private final long position;
    private final int shuffleBufferSize;
    private final boolean shuffleTransferToAllowed;
    private final FileChannel fileChannel;

    private ReadaheadRequest readaheadRequest;

    public FadvisedFileRegion(RandomAccessFile file, long position, long count, boolean manageOsCache,
            int readaheadLength, ReadaheadPool readaheadPool, String identifier, int shuffleBufferSize,
            boolean shuffleTransferToAllowed) throws IOException {
        super(file.getChannel(), position, count);
        this.manageOsCache = manageOsCache;
        this.readaheadLength = readaheadLength;
        this.readaheadPool = readaheadPool;
        this.fd = file.getFD();
        this.identifier = identifier;
        this.fileChannel = file.getChannel();
        this.count = count;
        this.position = position;
        this.shuffleBufferSize = shuffleBufferSize;
        this.shuffleTransferToAllowed = shuffleTransferToAllowed;
    }

    @Override
    public long transferTo(WritableByteChannel target, long position) throws IOException {
        if (readaheadPool != null && readaheadLength > 0) {
            readaheadRequest = readaheadPool.readaheadStream(identifier, fd, getPosition() + position,
                    readaheadLength, getPosition() + getCount(), readaheadRequest);
        }

        if (this.shuffleTransferToAllowed) {
            return super.transferTo(target, position);
        } else {
            return customShuffleTransfer(target, position);
        }
    }

    /**
     * This method transfers data using local buffer. It transfers data from 
     * a disk to a local buffer in memory, and then it transfers data from the 
     * buffer to the target. This is used only if transferTo is disallowed in
     * the configuration file. super.TransferTo does not perform well on Windows 
     * due to a small IO request generated. customShuffleTransfer can control 
     * the size of the IO requests by changing the size of the intermediate 
     * buffer.
     */
    @VisibleForTesting
    long customShuffleTransfer(WritableByteChannel target, long position) throws IOException {
        long actualCount = this.count - position;
        if (actualCount < 0 || position < 0) {
            throw new IllegalArgumentException(
                    "position out of range: " + position + " (expected: 0 - " + (this.count - 1) + ')');
        }
        if (actualCount == 0) {
            return 0L;
        }

        long trans = actualCount;
        int readSize;
        ByteBuffer byteBuffer = ByteBuffer.allocate(this.shuffleBufferSize);

        while (trans > 0L && (readSize = fileChannel.read(byteBuffer, this.position + position)) > 0) {
            //adjust counters and buffer limit
            if (readSize < trans) {
                trans -= readSize;
                position += readSize;
                byteBuffer.flip();
            } else {
                //We can read more than we need if the actualCount is not multiple 
                //of the byteBuffer size and file is big enough. In that case we cannot
                //use flip method but we need to set buffer limit manually to trans.
                byteBuffer.limit((int) trans);
                byteBuffer.position(0);
                position += trans;
                trans = 0;
            }

            //write data to the target
            while (byteBuffer.hasRemaining()) {
                target.write(byteBuffer);
            }

            byteBuffer.clear();
        }

        return actualCount - trans;
    }

    @Override
    public void releaseExternalResources() {
        if (readaheadRequest != null) {
            readaheadRequest.cancel();
        }
        super.releaseExternalResources();
    }

    /**
     * Call when the transfer completes successfully so we can advise the OS that
     * we don't need the region to be cached anymore.
     */
    public void transferSuccessful() {
        if (manageOsCache && getCount() > 0) {
            try {
                NativeIO.POSIX.getCacheManipulator().posixFadviseIfPossible(identifier, fd, getPosition(),
                        getCount(), POSIX_FADV_DONTNEED);
            } catch (Throwable t) {
                LOG.warn("Failed to manage OS cache for " + identifier, t);
            }
        }
    }
}