Java tutorial
/* * 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.server; import io.netty.channel.ChannelHandlerContext; import io.netty.channel.ChannelInboundHandlerAdapter; import io.netty.handler.timeout.IdleState; import io.netty.handler.timeout.IdleStateEvent; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.apache.spark.network.client.TransportClient; import org.apache.spark.network.client.TransportResponseHandler; import org.apache.spark.network.protocol.RequestMessage; import org.apache.spark.network.protocol.ResponseMessage; import static org.apache.spark.network.util.NettyUtils.getRemoteAddress; /** * The single Transport-level Channel handler which is used for delegating requests to the * {@link TransportRequestHandler} and responses to the {@link TransportResponseHandler}. * * All channels created in the transport layer are bidirectional. When the Client initiates a Netty * Channel with a RequestMessage (which gets handled by the Server's RequestHandler), the Server * will produce a ResponseMessage (handled by the Client's ResponseHandler). However, the Server * also gets a handle on the same Channel, so it may then begin to send RequestMessages to the * Client. * This means that the Client also needs a RequestHandler and the Server needs a ResponseHandler, * for the Client's responses to the Server's requests. * * This class also handles timeouts from a {@link io.netty.handler.timeout.IdleStateHandler}. * We consider a connection timed out if there are outstanding fetch or RPC requests but no traffic * on the channel for at least `requestTimeoutMs`. Note that this is duplex traffic; we will not * timeout if the client is continuously sending but getting no responses, for simplicity. */ public class TransportChannelHandler extends ChannelInboundHandlerAdapter { private static final Logger logger = LoggerFactory.getLogger(TransportChannelHandler.class); private final TransportClient client; private final TransportResponseHandler responseHandler; private final TransportRequestHandler requestHandler; private final long requestTimeoutNs; private final boolean closeIdleConnections; public TransportChannelHandler(TransportClient client, TransportResponseHandler responseHandler, TransportRequestHandler requestHandler, long requestTimeoutMs, boolean closeIdleConnections) { this.client = client; this.responseHandler = responseHandler; this.requestHandler = requestHandler; this.requestTimeoutNs = requestTimeoutMs * 1000L * 1000; this.closeIdleConnections = closeIdleConnections; } public TransportClient getClient() { return client; } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { logger.warn("Exception in connection from " + getRemoteAddress(ctx.channel()), cause); requestHandler.exceptionCaught(cause); responseHandler.exceptionCaught(cause); ctx.close(); } @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { try { requestHandler.channelActive(); } catch (RuntimeException e) { logger.error("Exception from request handler while channel is active", e); } try { responseHandler.channelActive(); } catch (RuntimeException e) { logger.error("Exception from response handler while channel is active", e); } super.channelActive(ctx); } @Override public void channelInactive(ChannelHandlerContext ctx) throws Exception { try { requestHandler.channelInactive(); } catch (RuntimeException e) { logger.error("Exception from request handler while channel is inactive", e); } try { responseHandler.channelInactive(); } catch (RuntimeException e) { logger.error("Exception from response handler while channel is inactive", e); } super.channelInactive(ctx); } @Override public void channelRead(ChannelHandlerContext ctx, Object request) throws Exception { if (request instanceof RequestMessage) { requestHandler.handle((RequestMessage) request); } else if (request instanceof ResponseMessage) { responseHandler.handle((ResponseMessage) request); } else { ctx.fireChannelRead(request); } } /** Triggered based on events from an {@link io.netty.handler.timeout.IdleStateHandler}. */ @Override public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception { if (evt instanceof IdleStateEvent) { IdleStateEvent e = (IdleStateEvent) evt; // See class comment for timeout semantics. In addition to ensuring we only timeout while // there are outstanding requests, we also do a secondary consistency check to ensure // there's no race between the idle timeout and incrementing the numOutstandingRequests // (see SPARK-7003). // // To avoid a race between TransportClientFactory.createClient() and this code which could // result in an inactive client being returned, this needs to run in a synchronized block. synchronized (this) { boolean isActuallyOverdue = System.nanoTime() - responseHandler.getTimeOfLastRequestNs() > requestTimeoutNs; if (e.state() == IdleState.ALL_IDLE && isActuallyOverdue) { if (responseHandler.numOutstandingRequests() > 0) { String address = getRemoteAddress(ctx.channel()); logger.error("Connection to {} has been quiet for {} ms while there are outstanding " + "requests. Assuming connection is dead; please adjust spark.network.timeout if " + "this is wrong.", address, requestTimeoutNs / 1000 / 1000); client.timeOut(); ctx.close(); } else if (closeIdleConnections) { // While CloseIdleConnections is enable, we also close idle connection client.timeOut(); ctx.close(); } } } } ctx.fireUserEventTriggered(evt); } public TransportResponseHandler getResponseHandler() { return responseHandler; } }