alluxio.worker.netty.DataServerBlockReadHandler.java Source code

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Here is the source code for alluxio.worker.netty.DataServerBlockReadHandler.java

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/*
 * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
 * (the "License"). You may not use this work except in compliance with the License, which is
 * available at www.apache.org/licenses/LICENSE-2.0
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied, as more fully set forth in the License.
 *
 * See the NOTICE file distributed with this work for information regarding copyright ownership.
 */

package alluxio.worker.netty;

import alluxio.metrics.MetricsSystem;
import alluxio.network.protocol.RPCProtoMessage;
import alluxio.network.protocol.databuffer.DataBuffer;
import alluxio.network.protocol.databuffer.DataFileChannel;
import alluxio.network.protocol.databuffer.DataNettyBufferV2;
import alluxio.proto.dataserver.Protocol;
import alluxio.worker.block.BlockWorker;
import alluxio.worker.block.io.BlockReader;

import com.codahale.metrics.Counter;
import com.google.common.base.Preconditions;
import io.netty.buffer.ByteBuf;
import io.netty.channel.Channel;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;
import java.nio.channels.FileChannel;
import java.util.concurrent.ExecutorService;

import javax.annotation.concurrent.NotThreadSafe;

/**
 * This handler handles block read request. Check more information in {@link DataServerReadHandler}.
 */
@NotThreadSafe
final class DataServerBlockReadHandler extends DataServerReadHandler {
    private static final Logger LOG = LoggerFactory.getLogger(DataServerBlockReadHandler.class);

    /** The Block Worker which handles blocks stored in the Alluxio storage of the worker. */
    private final BlockWorker mWorker;
    /** The transfer type used by the data server. */
    private final FileTransferType mTransferType;

    /**
     * The block read request internal representation.
     */
    private final class BlockReadRequestInternal extends ReadRequestInternal {
        final BlockReader mBlockReader;

        /**
         * Creates an instance of {@link BlockReadRequestInternal}.
         *
         * @param request the block read request
         * @throws Exception if it fails to create the object
         */
        BlockReadRequestInternal(Protocol.ReadRequest request) throws Exception {
            super(request.getId(), request.getOffset(), request.getOffset() + request.getLength());
            mBlockReader = mWorker.readBlockRemote(request.getSessionId(), request.getId(), request.getLockId());
            mWorker.accessBlock(request.getSessionId(), mId);

            ((FileChannel) mBlockReader.getChannel()).position(mStart);
        }

        @Override
        public void close() throws IOException {
            if (mBlockReader != null) {
                mBlockReader.close();
            }
        }
    }

    /**
     * Creates an instance of {@link DataServerReadHandler}.
     *
     * @param executorService the executor service to run {@link PacketReader}s
     * @param blockWorker the block worker
     * @param fileTransferType the file transfer type
     */
    DataServerBlockReadHandler(ExecutorService executorService, BlockWorker blockWorker,
            FileTransferType fileTransferType) {
        super(executorService);
        mWorker = blockWorker;
        mTransferType = fileTransferType;
    }

    @Override
    protected boolean acceptMessage(Object object) {
        if (!super.acceptMessage(object)) {
            return false;
        }
        Protocol.ReadRequest request = ((RPCProtoMessage) object).getMessage().getMessage();
        return request.getType() == Protocol.RequestType.ALLUXIO_BLOCK;
    }

    @Override
    protected void initializeRequest(Protocol.ReadRequest request) throws Exception {
        mRequest = new BlockReadRequestInternal(request);
    }

    @Override
    protected DataBuffer getDataBuffer(Channel channel, long offset, int len) throws IOException {
        BlockReader blockReader = ((BlockReadRequestInternal) mRequest).mBlockReader;
        Preconditions.checkArgument(blockReader.getChannel() instanceof FileChannel,
                "Only FileChannel is supported!");
        switch (mTransferType) {
        case MAPPED:
            ByteBuf buf = channel.alloc().buffer(len, len);
            try {
                FileChannel fileChannel = (FileChannel) blockReader.getChannel();
                Preconditions.checkState(fileChannel.position() == offset);
                while (buf.writableBytes() > 0 && buf.writeBytes(fileChannel, buf.writableBytes()) != -1) {
                }
                return new DataNettyBufferV2(buf);
            } catch (Throwable e) {
                buf.release();
                throw e;
            }
        case TRANSFER: // intend to fall through as TRANSFER is the default type.
        default:
            return new DataFileChannel((FileChannel) blockReader.getChannel(), offset, len);
        }
    }

    @Override
    protected void incrementMetrics(long bytesRead) {
        Metrics.BYTES_READ_REMOTE.inc(bytesRead);
    }

    /**
     * Class that contains metrics for BlockDataServerHandler.
     */
    private static final class Metrics {
        private static final Counter BYTES_READ_REMOTE = MetricsSystem.workerCounter("BytesReadRemote");

        private Metrics() {
        } // prevent instantiation
    }
}