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

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Here is the source code for org.apache.hadoop.mapred.FadvisedChunkedFile.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 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.handler.stream.ChunkedFile;

public class FadvisedChunkedFile extends ChunkedFile {

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

    private final boolean manageOsCache;
    private final int readaheadLength;
    private final ReadaheadPool readaheadPool;
    private final FileDescriptor fd;
    private final String identifier;

    private ReadaheadRequest readaheadRequest;

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

    @Override
    public Object nextChunk() throws Exception {
        if (manageOsCache && readaheadPool != null) {
            readaheadRequest = readaheadPool.readaheadStream(identifier, fd, getCurrentOffset(), readaheadLength,
                    getEndOffset(), readaheadRequest);
        }
        return super.nextChunk();
    }

    @Override
    public void close() throws Exception {
        if (readaheadRequest != null) {
            readaheadRequest.cancel();
        }
        if (manageOsCache && getEndOffset() - getStartOffset() > 0) {
            try {
                NativeIO.POSIX.getCacheManipulator().posixFadviseIfPossible(identifier, fd, getStartOffset(),
                        getEndOffset() - getStartOffset(), POSIX_FADV_DONTNEED);
            } catch (Throwable t) {
                LOG.warn("Failed to manage OS cache for " + identifier, t);
            }
        }
        super.close();
    }
}