rocketmq-netty通信设计-request和response

chudaxiakkk

已于 2025-02-14 14:06:08 修改

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分类专栏： rocketmq源码解读专栏文章标签： rocketmq netty通信

于 2025-02-13 18:30:41 首次发布

本文链接：https://blog.youkuaiyun.com/chudaxiakkk/article/details/145616888

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1、NettyRemotingServer启动分析

org.apache.rocketmq.remoting.netty.NettyRemotingServer#start

public void start() {
   
        this.defaultEventExecutorGroup = new DefaultEventExecutorGroup(
            nettyServerConfig.getServerWorkerThreads(),
            new ThreadFactory() {
   

                private AtomicInteger threadIndex = new AtomicInteger(0);

                @Override
                public Thread newThread(Runnable r) {
   
                    return new Thread(r, "NettyServerCodecThread_" + this.threadIndex.incrementAndGet());
                }
            });

        prepareSharableHandlers();

        ServerBootstrap childHandler =
            this.serverBootstrap.group(this.eventLoopGroupBoss, this.eventLoopGroupSelector)
                .channel(useEpoll() ? EpollServerSocketChannel.class : NioServerSocketChannel.class)
                .option(ChannelOption.SO_BACKLOG, nettyServerConfig.getServerSocketBacklog())
                .option(ChannelOption.SO_REUSEADDR, true)
                .option(ChannelOption.SO_KEEPALIVE, false)
                .childOption(ChannelOption.TCP_NODELAY, true)
                .localAddress(new InetSocketAddress(this.nettyServerConfig.getListenPort()))
                .childHandler(new ChannelInitializer<SocketChannel>() {
   
                    @Override
                    public void initChannel(SocketChannel ch) throws Exception {
   
                        ch.pipeline()
                            .addLast(defaultEventExecutorGroup, HANDSHAKE_HANDLER_NAME, handshakeHandler)
                            .addLast(defaultEventExecutorGroup,
                                encoder,
                                new NettyDecoder(),
                                new IdleStateHandler(0, 0, nettyServerConfig.getServerChannelMaxIdleTimeSeconds()),
                                connectionManageHandler,
                                serverHandler
                            );
                    }
                });

ServerBootstrap是netty作为服务端的启动入口。首先绑定了两个线程池。也就是boss线程池、worker线程池。
这里分析，也就是eventLoopGroupBoss和eventLoopGroupSelector

ServerBootstrap启动分析

查看初始化源码

if (useEpoll()) {
   
    this.eventLoopGroupBoss = new EpollEventLoopGroup(1, new ThreadFactory() {
   
        private AtomicInteger threadIndex = new AtomicInteger(0);

        @Override
        public Thread newThread(Runnable r) {
   
            return new Thread(r, String.format("NettyEPOLLBoss_%d", this.threadIndex.incrementAndGet()));
        }
    });

    this.eventLoopGroupSelector = new EpollEventLoopGroup(nettyServerConfig.getServerSelectorThreads(), new ThreadFactory() {
   
        private AtomicInteger threadIndex = new AtomicInteger(0);
        private int threadTotal = nettyServerConfig.getServerSelectorThreads();

        @Override
        public Thread newThread(Runnable r) {
   
            return new Thread(r, String.format("NettyServerEPOLLSelector_%d_%d", threadTotal, this.threadIndex.incrementAndGet()));
        }
    });
} else {
   
    this.eventLoopGroupBoss = new NioEventLoopGroup(1, new ThreadFactory() {
   
        private AtomicInteger threadIndex = new AtomicInteger(0);

        @Override
        public Thread newThread(Runnable r) {
   
            return new Thread(r, String.format("NettyNIOBoss_%d", this.threadIndex.incrementAndGet()));
        }
    });

    this.eventLoopGroupSelector = new NioEventLoopGroup(nettyServerConfig.getServerSelectorThreads(), new ThreadFactory() {
   
        private AtomicInteger threadIndex = new AtomicInteger(0);
        private int threadTotal = nettyServerConfig.getServerSelectorThreads();

        @Override
        public Thread newThread(Runnable r) {
   
            return new Thread(r, String.format("NettyServerNIOSelector_%d_%d", threadTotal, this.threadIndex.incrementAndGet()));
        }
    });
}

不同平台，实现方式不一样。linux上会使用Epoll，其他会使用java提供的跨平台的NIO
eventLoopGroupBoss默认线程数是1
eventLoopGroupSelector默认线程数是3

再看defaultEventExecutorGroup。
.childHandler()方式指定了channelHandle的线程池。看线程名称NettyServerCodecThread_，可猜测该线程池主要功能是做编码解码。

.addLast(defaultEventExecutorGroup, HANDSHAKE_HANDLER_NAME, handshakeHandler)
目的是做TSL的加解密
.addLast(defaultEventExecutorGroup,
encoder,
new NettyDecoder(),
new IdleStateHandler(0, 0, nettyServerConfig.getServerChannelMaxIdleTimeSeconds()),
connectionManageHandler,
serverHandler
);

encoder是做编码。将本地msg转成byte[]，传输到远端
NettyDecoder是做解码，将远端byte[]解码成本地msg。这里比较关键。将请求体转换成RemotingCommand类。详情看org.apache.rocketmq.remoting.netty.NettyDecoder#decode

connectionManageHandler 看代码可知，是channel有特定事件时打印日志。注册、取消注册、激活、取消激活等
serverHandler就是业务的request、response处理类。处理RemotingCommand消息

class NettyServerHandler extends SimpleChannelInboundHandler<RemotingCommand> {
   

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {
   
            processMessageReceived(ctx, msg);
        }
    }

查看NettyServerHandler 的处理流程

org.apache.rocketmq.remoting.netty.NettyRemotingAbstract#processRequestCommand

public void processRequestCommand(final ChannelHandlerContext ctx, final RemotingCommand cmd) {
   
        final Pair<NettyRequestProcessor,

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