org.apache.spark.network.client.TransportClient.java Source code

Java tutorial

Introduction

Here is the source code for org.apache.spark.network.client.TransportClient.java

Source

/*
 * 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.spark.network.client;

import java.io.Closeable;
import java.io.IOException;
import java.net.SocketAddress;
import java.nio.ByteBuffer;
import java.util.UUID;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import javax.annotation.Nullable;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Objects;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import com.google.common.util.concurrent.SettableFuture;
import io.netty.channel.Channel;
import io.netty.util.concurrent.Future;
import io.netty.util.concurrent.GenericFutureListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.spark.network.buffer.ManagedBuffer;
import org.apache.spark.network.buffer.NioManagedBuffer;
import org.apache.spark.network.protocol.*;

import static org.apache.spark.network.util.NettyUtils.getRemoteAddress;

/**
 * Client for fetching consecutive chunks of a pre-negotiated stream. This API is intended to allow
 * efficient transfer of a large amount of data, broken up into chunks with size ranging from
 * hundreds of KB to a few MB.
 *
 * Note that while this client deals with the fetching of chunks from a stream (i.e., data plane),
 * the actual setup of the streams is done outside the scope of the transport layer. The convenience
 * method "sendRPC" is provided to enable control plane communication between the client and server
 * to perform this setup.
 *
 * For example, a typical workflow might be:
 * client.sendRPC(new OpenFile("/foo")) --> returns StreamId = 100
 * client.fetchChunk(streamId = 100, chunkIndex = 0, callback)
 * client.fetchChunk(streamId = 100, chunkIndex = 1, callback)
 * ...
 * client.sendRPC(new CloseStream(100))
 *
 * Construct an instance of TransportClient using {@link TransportClientFactory}. A single
 * TransportClient may be used for multiple streams, but any given stream must be restricted to a
 * single client, in order to avoid out-of-order responses.
 *
 * NB: This class is used to make requests to the server, while {@link TransportResponseHandler} is
 * responsible for handling responses from the server.
 *
 * Concurrency: thread safe and can be called from multiple threads.
 */
public class TransportClient implements Closeable {
    private static final Logger logger = LoggerFactory.getLogger(TransportClient.class);

    private final Channel channel;
    private final TransportResponseHandler handler;
    @Nullable
    private String clientId;
    private volatile boolean timedOut;

    public TransportClient(Channel channel, TransportResponseHandler handler) {
        this.channel = Preconditions.checkNotNull(channel);
        this.handler = Preconditions.checkNotNull(handler);
        this.timedOut = false;
    }

    public Channel getChannel() {
        return channel;
    }

    public boolean isActive() {
        return !timedOut && (channel.isOpen() || channel.isActive());
    }

    public SocketAddress getSocketAddress() {
        return channel.remoteAddress();
    }

    /**
     * Returns the ID used by the client to authenticate itself when authentication is enabled.
     *
     * @return The client ID, or null if authentication is disabled.
     */
    public String getClientId() {
        return clientId;
    }

    /**
     * Sets the authenticated client ID. This is meant to be used by the authentication layer.
     *
     * Trying to set a different client ID after it's been set will result in an exception.
     */
    public void setClientId(String id) {
        Preconditions.checkState(clientId == null, "Client ID has already been set.");
        this.clientId = id;
    }

    /**
     * Requests a single chunk from the remote side, from the pre-negotiated streamId.
     *
     * Chunk indices go from 0 onwards. It is valid to request the same chunk multiple times, though
     * some streams may not support this.
     *
     * Multiple fetchChunk requests may be outstanding simultaneously, and the chunks are guaranteed
     * to be returned in the same order that they were requested, assuming only a single
     * TransportClient is used to fetch the chunks.
     *
     * @param streamId Identifier that refers to a stream in the remote StreamManager. This should
     *                 be agreed upon by client and server beforehand.
     * @param chunkIndex 0-based index of the chunk to fetch
     * @param callback Callback invoked upon successful receipt of chunk, or upon any failure.
     */
    public void fetchChunk(long streamId, int chunkIndex, ChunkReceivedCallback callback) {
        if (logger.isDebugEnabled()) {
            logger.debug("Sending fetch chunk request {} to {}", chunkIndex, getRemoteAddress(channel));
        }

        StreamChunkId streamChunkId = new StreamChunkId(streamId, chunkIndex);
        StdChannelListener listener = new StdChannelListener(streamChunkId) {
            @Override
            void handleFailure(String errorMsg, Throwable cause) {
                handler.removeFetchRequest(streamChunkId);
                callback.onFailure(chunkIndex, new IOException(errorMsg, cause));
            }
        };
        handler.addFetchRequest(streamChunkId, callback);

        channel.writeAndFlush(new ChunkFetchRequest(streamChunkId)).addListener(listener);
    }

    /**
     * Request to stream the data with the given stream ID from the remote end.
     *
     * @param streamId The stream to fetch.
     * @param callback Object to call with the stream data.
     */
    public void stream(String streamId, StreamCallback callback) {
        StdChannelListener listener = new StdChannelListener(streamId) {
            @Override
            void handleFailure(String errorMsg, Throwable cause) throws Exception {
                callback.onFailure(streamId, new IOException(errorMsg, cause));
            }
        };
        if (logger.isDebugEnabled()) {
            logger.debug("Sending stream request for {} to {}", streamId, getRemoteAddress(channel));
        }

        // Need to synchronize here so that the callback is added to the queue and the RPC is
        // written to the socket atomically, so that callbacks are called in the right order
        // when responses arrive.
        synchronized (this) {
            handler.addStreamCallback(streamId, callback);
            channel.writeAndFlush(new StreamRequest(streamId)).addListener(listener);
        }
    }

    /**
     * Sends an opaque message to the RpcHandler on the server-side. The callback will be invoked
     * with the server's response or upon any failure.
     *
     * @param message The message to send.
     * @param callback Callback to handle the RPC's reply.
     * @return The RPC's id.
     */
    public long sendRpc(ByteBuffer message, RpcResponseCallback callback) {
        if (logger.isTraceEnabled()) {
            logger.trace("Sending RPC to {}", getRemoteAddress(channel));
        }

        long requestId = requestId();
        handler.addRpcRequest(requestId, callback);

        RpcChannelListener listener = new RpcChannelListener(requestId, callback);
        channel.writeAndFlush(new RpcRequest(requestId, new NioManagedBuffer(message))).addListener(listener);

        return requestId;
    }

    /**
     * Send data to the remote end as a stream.  This differs from stream() in that this is a request
     * to *send* data to the remote end, not to receive it from the remote.
     *
     * @param meta meta data associated with the stream, which will be read completely on the
     *             receiving end before the stream itself.
     * @param data this will be streamed to the remote end to allow for transferring large amounts
     *             of data without reading into memory.
     * @param callback handles the reply -- onSuccess will only be called when both message and data
     *                 are received successfully.
     */
    public long uploadStream(ManagedBuffer meta, ManagedBuffer data, RpcResponseCallback callback) {
        if (logger.isTraceEnabled()) {
            logger.trace("Sending RPC to {}", getRemoteAddress(channel));
        }

        long requestId = requestId();
        handler.addRpcRequest(requestId, callback);

        RpcChannelListener listener = new RpcChannelListener(requestId, callback);
        channel.writeAndFlush(new UploadStream(requestId, meta, data)).addListener(listener);

        return requestId;
    }

    /**
     * Synchronously sends an opaque message to the RpcHandler on the server-side, waiting for up to
     * a specified timeout for a response.
     */
    public ByteBuffer sendRpcSync(ByteBuffer message, long timeoutMs) {
        final SettableFuture<ByteBuffer> result = SettableFuture.create();

        sendRpc(message, new RpcResponseCallback() {
            @Override
            public void onSuccess(ByteBuffer response) {
                try {
                    ByteBuffer copy = ByteBuffer.allocate(response.remaining());
                    copy.put(response);
                    // flip "copy" to make it readable
                    copy.flip();
                    result.set(copy);
                } catch (Throwable t) {
                    logger.warn("Error in responding PRC callback", t);
                    result.setException(t);
                }
            }

            @Override
            public void onFailure(Throwable e) {
                result.setException(e);
            }
        });

        try {
            return result.get(timeoutMs, TimeUnit.MILLISECONDS);
        } catch (ExecutionException e) {
            throw Throwables.propagate(e.getCause());
        } catch (Exception e) {
            throw Throwables.propagate(e);
        }
    }

    /**
     * Sends an opaque message to the RpcHandler on the server-side. No reply is expected for the
     * message, and no delivery guarantees are made.
     *
     * @param message The message to send.
     */
    public void send(ByteBuffer message) {
        channel.writeAndFlush(new OneWayMessage(new NioManagedBuffer(message)));
    }

    /**
     * Removes any state associated with the given RPC.
     *
     * @param requestId The RPC id returned by {@link #sendRpc(ByteBuffer, RpcResponseCallback)}.
     */
    public void removeRpcRequest(long requestId) {
        handler.removeRpcRequest(requestId);
    }

    /** Mark this channel as having timed out. */
    public void timeOut() {
        this.timedOut = true;
    }

    @VisibleForTesting
    public TransportResponseHandler getHandler() {
        return handler;
    }

    @Override
    public void close() {
        // close is a local operation and should finish with milliseconds; timeout just to be safe
        channel.close().awaitUninterruptibly(10, TimeUnit.SECONDS);
    }

    @Override
    public String toString() {
        return Objects.toStringHelper(this).add("remoteAdress", channel.remoteAddress()).add("clientId", clientId)
                .add("isActive", isActive()).toString();
    }

    private static long requestId() {
        return Math.abs(UUID.randomUUID().getLeastSignificantBits());
    }

    private class StdChannelListener implements GenericFutureListener<Future<? super Void>> {
        final long startTime;
        final Object requestId;

        StdChannelListener(Object requestId) {
            this.startTime = System.currentTimeMillis();
            this.requestId = requestId;
        }

        @Override
        public void operationComplete(Future<? super Void> future) throws Exception {
            if (future.isSuccess()) {
                if (logger.isTraceEnabled()) {
                    long timeTaken = System.currentTimeMillis() - startTime;
                    logger.trace("Sending request {} to {} took {} ms", requestId, getRemoteAddress(channel),
                            timeTaken);
                }
            } else {
                String errorMsg = String.format("Failed to send RPC %s to %s: %s", requestId,
                        getRemoteAddress(channel), future.cause());
                logger.error(errorMsg, future.cause());
                channel.close();
                try {
                    handleFailure(errorMsg, future.cause());
                } catch (Exception e) {
                    logger.error("Uncaught exception in RPC response callback handler!", e);
                }
            }
        }

        void handleFailure(String errorMsg, Throwable cause) throws Exception {
        }
    }

    private class RpcChannelListener extends StdChannelListener {
        final long rpcRequestId;
        final RpcResponseCallback callback;

        RpcChannelListener(long rpcRequestId, RpcResponseCallback callback) {
            super("RPC " + rpcRequestId);
            this.rpcRequestId = rpcRequestId;
            this.callback = callback;
        }

        @Override
        void handleFailure(String errorMsg, Throwable cause) {
            handler.removeRpcRequest(rpcRequestId);
            callback.onFailure(new IOException(errorMsg, cause));
        }
    }

}