alluxio.client.netty.NettyUnderFileSystemFileReader.java Source code

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Here is the source code for alluxio.client.netty.NettyUnderFileSystemFileReader.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.client.netty;

import alluxio.Constants;
import alluxio.exception.ExceptionMessage;
import alluxio.network.protocol.RPCErrorResponse;
import alluxio.network.protocol.RPCFileReadRequest;
import alluxio.network.protocol.RPCFileReadResponse;
import alluxio.network.protocol.RPCMessage;
import alluxio.network.protocol.RPCResponse;

import io.netty.bootstrap.Bootstrap;
import io.netty.channel.Channel;
import io.netty.channel.ChannelFuture;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.Closeable;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.util.concurrent.TimeUnit;

import javax.annotation.concurrent.NotThreadSafe;

/**
 * Reader for an under file system file through a worker's data server. This class does not hold
 * any state specific to the file being read and can be used to read multiple files, but not
 * concurrently. Close should be called on the reader if the caller no longer intends to use the
 * reader in order to clean up any lingering data from the last read.
 */
@NotThreadSafe
public final class NettyUnderFileSystemFileReader implements Closeable {
    private static final Logger LOG = LoggerFactory.getLogger(Constants.LOGGER_TYPE);

    /** Netty bootstrap for the connection. */
    private final Bootstrap mClientBootstrap;
    /** Handler for Netty messages. */
    private final ClientHandler mHandler;
    /** A reference to read response so we can explicitly release the resource after reading. */
    private RPCFileReadResponse mReadResponse;

    /**
     * Creates a new reader for a file in an under file system through a worker's data server.
     */
    public NettyUnderFileSystemFileReader() {
        mHandler = new ClientHandler();
        mClientBootstrap = NettyClient.createClientBootstrap(mHandler);
    }

    /**
     * Reads data from the specified worker for a file in the under file system.
     *
     * @param address the worker address to read from
     * @param ufsFileId the worker specific file id referencing the file to read
     * @param offset the offset in the file to read from
     * @param length the length to read
     * @return a byte buffer with the requested data, null if EOF is reached
     * @throws IOException if an error occurs communicating with the worker
     */
    public ByteBuffer read(InetSocketAddress address, long ufsFileId, long offset, long length) throws IOException {
        // For a zero length read, directly return without trying the Netty call.
        if (length == 0) {
            return ByteBuffer.allocate(0);
        }
        SingleResponseListener listener = null;
        try {
            ChannelFuture f = mClientBootstrap.connect(address).sync();

            LOG.debug("Connected to remote machine {}", address);
            Channel channel = f.channel();
            listener = new SingleResponseListener();
            mHandler.addListener(listener);
            channel.writeAndFlush(new RPCFileReadRequest(ufsFileId, offset, length));

            RPCResponse response = listener.get(NettyClient.TIMEOUT_MS, TimeUnit.MILLISECONDS);
            channel.close().sync();

            switch (response.getType()) {
            case RPC_FILE_READ_RESPONSE:
                RPCFileReadResponse resp = (RPCFileReadResponse) response;
                LOG.debug("Data for ufs file id {} from machine {} received", ufsFileId, address);
                RPCResponse.Status status = resp.getStatus();
                if (status == RPCResponse.Status.SUCCESS) {
                    // always clear the previous response before reading another one
                    cleanup();
                    // End of file reached
                    if (resp.isEOF()) {
                        return null;
                    }
                    mReadResponse = resp;
                    return resp.getPayloadDataBuffer().getReadOnlyByteBuffer();
                }
                throw new IOException(status.getMessage() + " response: " + resp);
            case RPC_ERROR_RESPONSE:
                RPCErrorResponse error = (RPCErrorResponse) response;
                throw new IOException(error.getStatus().getMessage());
            default:
                throw new IOException(ExceptionMessage.UNEXPECTED_RPC_RESPONSE.getMessage(response.getType(),
                        RPCMessage.Type.RPC_FILE_READ_RESPONSE));
            }
        } catch (Exception e) {
            throw new IOException(e);
        } finally {
            if (listener != null) {
                mHandler.removeListener(listener);
            }
        }
    }

    /**
     * {@inheritDoc}
     *
     * Releases the underlying buffer of previous/current read response.
     */
    @Override
    public void close() {
        cleanup();
    }

    /**
     * Releases the underlying buffer of previous/current read response.
     */
    private void cleanup() {
        if (mReadResponse != null) {
            mReadResponse.getPayloadDataBuffer().release();
            mReadResponse = null;
        }
    }
}