[SPARK-24355] Spark external shuffle server improvement to better handle block fetch requests. #22173
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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. | ||
| */ | ||
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| package org.apache.spark.network.server; | ||
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| import java.net.SocketAddress; | ||
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| import com.google.common.base.Throwables; | ||
| import io.netty.channel.Channel; | ||
| import io.netty.channel.ChannelFuture; | ||
| import io.netty.channel.ChannelFutureListener; | ||
| import io.netty.channel.ChannelHandlerContext; | ||
| import io.netty.channel.SimpleChannelInboundHandler; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
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| import org.apache.spark.network.buffer.ManagedBuffer; | ||
| import org.apache.spark.network.client.TransportClient; | ||
| import org.apache.spark.network.protocol.ChunkFetchFailure; | ||
| import org.apache.spark.network.protocol.ChunkFetchRequest; | ||
| import org.apache.spark.network.protocol.ChunkFetchSuccess; | ||
| import org.apache.spark.network.protocol.Encodable; | ||
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| import static org.apache.spark.network.util.NettyUtils.*; | ||
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| /** | ||
| * A dedicated ChannelHandler for processing ChunkFetchRequest messages. When sending response | ||
| * of ChunkFetchRequest messages to the clients, the thread performing the I/O on the underlying | ||
| * channel could potentially be blocked due to disk contentions. If several hundreds of clients | ||
| * send ChunkFetchRequest to the server at the same time, it could potentially occupying all | ||
| * threads from TransportServer's default EventLoopGroup for waiting for disk reads before it | ||
| * can send the block data back to the client as part of the ChunkFetchSuccess messages. As a | ||
| * result, it would leave no threads left to process other RPC messages, which takes much less | ||
| * time to process, and could lead to client timing out on either performing SASL authentication, | ||
| * registering executors, or waiting for response for an OpenBlocks messages. | ||
| */ | ||
| public class ChunkFetchRequestHandler extends SimpleChannelInboundHandler<ChunkFetchRequest> { | ||
| private static final Logger logger = LoggerFactory.getLogger(ChunkFetchRequestHandler.class); | ||
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| private final TransportClient client; | ||
| private final StreamManager streamManager; | ||
| /** The max number of chunks being transferred and not finished yet. */ | ||
| private final long maxChunksBeingTransferred; | ||
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| public ChunkFetchRequestHandler( | ||
| TransportClient client, | ||
| StreamManager streamManager, | ||
| Long maxChunksBeingTransferred) { | ||
| this.client = client; | ||
| this.streamManager = streamManager; | ||
| this.maxChunksBeingTransferred = maxChunksBeingTransferred; | ||
| } | ||
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| @Override | ||
| public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { | ||
| logger.warn("Exception in connection from " + getRemoteAddress(ctx.channel()), | ||
| cause); | ||
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| ctx.close(); | ||
| } | ||
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| @Override | ||
| protected void channelRead0(ChannelHandlerContext ctx, | ||
| final ChunkFetchRequest msg) throws Exception { | ||
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| Channel channel = ctx.channel(); | ||
| if (logger.isTraceEnabled()) { | ||
| logger.trace("Received req from {} to fetch block {}", getRemoteAddress(channel), | ||
| msg.streamChunkId); | ||
| } | ||
| long chunksBeingTransferred = streamManager.chunksBeingTransferred(); | ||
| if (chunksBeingTransferred >= maxChunksBeingTransferred) { | ||
| logger.warn("The number of chunks being transferred {} is above {}, close the connection.", | ||
| chunksBeingTransferred, maxChunksBeingTransferred); | ||
| channel.close(); | ||
| return; | ||
| } | ||
| ManagedBuffer buf; | ||
| try { | ||
| streamManager.checkAuthorization(client, msg.streamChunkId.streamId); | ||
| streamManager.registerChannel(channel, msg.streamChunkId.streamId); | ||
| buf = streamManager.getChunk(msg.streamChunkId.streamId, msg.streamChunkId.chunkIndex); | ||
| } catch (Exception e) { | ||
| logger.error(String.format("Error opening block %s for request from %s", | ||
| msg.streamChunkId, getRemoteAddress(channel)), e); | ||
| respond(channel, | ||
| new ChunkFetchFailure(msg.streamChunkId, | ||
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| Throwables.getStackTraceAsString(e))); | ||
| return; | ||
| } | ||
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| streamManager.chunkBeingSent(msg.streamChunkId.streamId); | ||
| respond(channel, new ChunkFetchSuccess(msg.streamChunkId, buf)).addListener( | ||
| (ChannelFutureListener) future -> streamManager.chunkSent(msg.streamChunkId.streamId)); | ||
| } | ||
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| /** | ||
| * The invocation to channel.writeAndFlush is async, and the actual I/O on the | ||
| * channel will be handled by the EventLoop the channel is registered to. So even | ||
| * though we are processing the ChunkFetchRequest in a separate thread pool, the actual I/O, | ||
| * which is the potentially blocking call that could deplete server handler threads, is still | ||
| * being processed by TransportServer's default EventLoopGroup. In order to throttle the max | ||
| * number of threads that channel I/O for sending response to ChunkFetchRequest, the thread | ||
| * calling channel.writeAndFlush will wait for the completion of sending response back to | ||
| * client by invoking sync(). This will throttle the rate at which threads from | ||
| * ChunkFetchRequest dedicated EventLoopGroup submit channel I/O requests to TransportServer's | ||
| * default EventLoopGroup, thus making sure that we can reserve some threads in | ||
| * TransportServer's default EventLoopGroup for handling other RPC messages. | ||
| */ | ||
| private ChannelFuture respond(final Channel channel, | ||
| final Encodable result) throws InterruptedException { | ||
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| final SocketAddress remoteAddress = channel.remoteAddress(); | ||
| return channel.writeAndFlush(result).sync().addListener((ChannelFutureListener) future -> { | ||
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| if (future.isSuccess()) { | ||
| logger.trace("Sent result {} to client {}", result, remoteAddress); | ||
| } else { | ||
| logger.error(String.format("Error sending result %s to %s; closing connection", | ||
| result, remoteAddress), future.cause()); | ||
| channel.close(); | ||
| } | ||
| }); | ||
| } | ||
| } | ||
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Is there any special reason that this must be a global one? I have not yet looked the details. But looks like this may cause ChunkFetchIntegrationSuite flaky as there is no isolation between tests.
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I haven't been able to reproduce this but the number of threads used for this tests are 2* number of cores or spark.shuffle.io.serverThreads.