前言

版本：RocketMQ4.4.0

RocketMQ架构

摘自《RocketMQ开发手册》

• Name Server是一个几乎无状态节点，可集群部署，节点之间无任何信息同步。
• Broker部署相对复杂，Broker分为Master和Slave，一个Master可以对应多个Slave，但是一个Slave只能对应一个Master，Master和Slave的对应关系通过指定相同的BrokerName，不同的BrokerId来定义，BrokerId为0表示Master，非0 表示Slave。Master也可以部署多个。每个Broker与NameServer集群中的所有节点建立长连接，定时注册Topic信息到所有NameServer。
• Producer和Name Server集群中的其中一个节点（随机选择）建立长连接，定期从Name Server获取Topic路由信息，并向提供Topic服务的Master建立长连接，且定时向Master发送心跳。Producer完全无状态，可集群部署。
• Consumer与Name Server集群中的其中一个节点（随机选择）建立长连接，定期从Name Server获取Topic路由信息，并向提供Topic服务的Master、Slave建立长连接，且定时向Master、Slave发送心跳。Consumer既可以从Master订阅消息，也可以从Slave订阅消息，订阅规则由Broker配置决定。

NameSrv集群是一个无状态节点，维护Broker注册的Topic信息，将向生产者和消费者提供Topic路由信息。

问题

看了RocketMQ架构，我们也大概了解了namesrv的作用，那么也产生了两个问题：

1. Broker注册信息，注册了哪些信息？也就是namesrv维护了集群中的哪些信息？
2. 由Broker定时上报注册信息，那么在Broker宕机时，无法注册信息，那么namesrv是如何处理已宕机的broker？

那么下面将进行阅读源码来解决这两个疑问。

Namesrv

RocketMQ包含的组件

• NameServer：单点，供Producer和Consumer获取Broker地址
• Producer：产生并发送消息
• Consumer：接收并消费消息
• Broker：消息存储，消息转发

namesrv组件

作用：Producer和Consumer获取Broker的地址。
目的：解耦Broker和Producer、Consumer。
原理：使用netty作为通信工具，监听指定端口，如果是broker注册，将broker的信息保存在内存中并保存到文件中，producer和consumer获取broker地址的请求

namesrv包结构说明

• NamesrvStartup为启动入口
• NamesrvController为启动控制器
• kvconfig为kv配置管理器
• processor为请求处理器，处理接收到的请求
• routeinfo为netty中实际存储路由信息的管理器/容器

NamesrvController包含的组件

• namesrvConfig：nameServer的配置
• nettyServerConfig：NameServer的netty配置
• remotingServer：NameServer 的netty服务器
• scheduledExecutorService：routeInfoManager和kvConfigManager使用的定时线程池
• remotingExecutor：netty使用的线程池
• brokerHosekeppingService：
• kvConfigManager：kv配置管理
• routeInfoManager：包含broker的ip和对应的队列信息，说明producer可以往哪一个broker发送消息，consumer从哪一个broker pull消息。
• fileWatchService：文件监控线程（4.3.0以上才拥有此功能）

NameServer启动

NamesrvStartup.main(0)

public static void main(String[] args) {
    main0(args);
}

public static NamesrvController main0(String[] args) {

    try {
        NamesrvController controller = createNamesrvController(args);
        start(controller);
        String tip = "The Name Server boot success. serializeType=" + RemotingCommand.getSerializeTypeConfigInThisServer();
        log.info(tip);
        System.out.printf("%s%n", tip);
        return controller;
    } catch (Throwable e) {
        e.printStackTrace();
        System.exit(-1);
    }

    return null;
}

public static NamesrvController createNamesrvController(String[] args) throws IOException, JoranException {
    System.setProperty(RemotingCommand.REMOTING_VERSION_KEY, Integer.toString(MQVersion.CURRENT_VERSION));
    //PackageConflictDetect.detectFastjson();

    Options options = ServerUtil.buildCommandlineOptions(new Options());
    commandLine = ServerUtil.parseCmdLine("mqnamesrv", args, buildCommandlineOptions(options), new PosixParser());
    if (null == commandLine) {
        System.exit(-1);
        return null;
    }
    //1.    NamesrvConfig配置
    final NamesrvConfig namesrvConfig = new NamesrvConfig();
    //2.    解析命令行参数，NettyServerConfig配置
    final NettyServerConfig nettyServerConfig = new NettyServerConfig();
    //配置监听端口
    nettyServerConfig.setListenPort(9876);
    if (commandLine.hasOption(‘c‘)) {
        String file = commandLine.getOptionValue(‘c‘);
        if (file != null) {
            InputStream in = new BufferedInputStream(new FileInputStream(file));
            properties = new Properties();
            properties.load(in);
            //读取properties文件，加载数据到内存对象中
            MixAll.properties2Object(properties, namesrvConfig);
            MixAll.properties2Object(properties, nettyServerConfig);

            namesrvConfig.setConfigStorePath(file);

            System.out.printf("load config properties file OK, %s%n", file);
            in.close();
        }
    }

    if (commandLine.hasOption(‘p‘)) {
        InternalLogger console = InternalLoggerFactory.getLogger(LoggerName.NAMESRV_CONSOLE_NAME);
        MixAll.printObjectProperties(console, namesrvConfig);
        MixAll.printObjectProperties(console, nettyServerConfig);
        System.exit(0);
    }

    MixAll.properties2Object(ServerUtil.commandLine2Properties(commandLine), namesrvConfig);

    if (null == namesrvConfig.getRocketmqHome()) {
        System.out.printf("Please set the %s variable in your environment to match the location of the RocketMQ installation%n", MixAll.ROCKETMQ_HOME_ENV);
        System.exit(-2);
    }
    //3.    logback配置
    LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory();
    JoranConfigurator configurator = new JoranConfigurator();
    configurator.setContext(lc);
    lc.reset();
    configurator.doConfigure(namesrvConfig.getRocketmqHome() + "/conf/logback_namesrv.xml");

    log = InternalLoggerFactory.getLogger(LoggerName.NAMESRV_LOGGER_NAME);

    MixAll.printObjectProperties(log, namesrvConfig);
    MixAll.printObjectProperties(log, nettyServerConfig);
    //4.    NamesrvController初始化，initialize
    final NamesrvController controller = new NamesrvController(namesrvConfig, nettyServerConfig);

    // remember all configs to prevent discard
    // 将读取的配置导入，防止丢失
    controller.getConfiguration().registerConfig(properties);

    return controller;
}

public static NamesrvController start(final NamesrvController controller) throws Exception {

    if (null == controller) {
        throw new IllegalArgumentException("NamesrvController is null");
    }

    boolean initResult = controller.initialize();
    if (!initResult) {
        controller.shutdown();
        System.exit(-3);
    }

    Runtime.getRuntime().addShutdownHook(new ShutdownHookThread(log, new Callable<Void>() {
        @Override
            public Void call() throws Exception {
            controller.shutdown();
            return null;
        }
    }));

    controller.start();

    return controller;
}

说明：

1. NamesrvConfig配置
2. 解析命令行参数，NettyServerConfig配置
3. logback配置
4. 创建NamesrvController并初始化参数。
5. NamesrvStartup.start()
6. NamesrvController.initialize()
7. 注册shutdown钩子
8. NamesrvController.start()

NamesrvController.initialize()

public boolean initialize() {
    //1.    KVConfigManager.load加载原来的key-value文件到内存中
    this.kvConfigManager.load();
    //2.    初始化NettyRemotingServer
    this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.brokerHousekeepingService);
    //3.    初始化nettyRomote线程池，默认8个，该线程池中队列为LinkedBlockingQueue，为无界队列
    this.remotingExecutor =
        Executors.newFixedThreadPool(nettyServerConfig.getServerWorkerThreads(), new ThreadFactoryImpl("RemotingExecutorThread_"));
    //4.    注册requestProcessor，默认为DefaultRequestProcessor，用来处理netty接收到的信息
    this.registerProcessor();
    //5.    启动定时线程，延迟5秒执行，每隔10s判断broker是否依然存活
    this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

        @Override
            public void run() {
            NamesrvController.this.routeInfoManager.scanNotActiveBroker();
        }
    }, 5, 10, TimeUnit.SECONDS);
    //6.    启动定时线程，延迟1秒执行，每隔10min打印出所有k-v
    this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

        @Override
            public void run() {
            NamesrvController.this.kvConfigManager.printAllPeriodically();
        }
    }, 1, 10, TimeUnit.MINUTES);

    if (TlsSystemConfig.tlsMode != TlsMode.DISABLED) {
        // Register a listener to reload SslContext
        try {
            fileWatchService = new FileWatchService(
                new String[]{
                    TlsSystemConfig.tlsServerCertPath,
                    TlsSystemConfig.tlsServerKeyPath,
                    TlsSystemConfig.tlsServerTrustCertPath
                },
                new FileWatchService.Listener() {
                    boolean certChanged, keyChanged = false;

                    @Override
                        public void onChanged(String path) {
                        if (path.equals(TlsSystemConfig.tlsServerTrustCertPath)) {
                            log.info("The trust certificate changed, reload the ssl context");
                            reloadServerSslContext();
                        }
                        if (path.equals(TlsSystemConfig.tlsServerCertPath)) {
                            certChanged = true;
                        }
                        if (path.equals(TlsSystemConfig.tlsServerKeyPath)) {
                            keyChanged = true;
                        }
                        if (certChanged && keyChanged) {
                            log.info("The certificate and private key changed, reload the ssl context");
                            certChanged = keyChanged = false;
                            reloadServerSslContext();
                        }
                    }

                    private void reloadServerSslContext() {
                        ((NettyRemotingServer) remotingServer).loadSslContext();
                    }
                });
        } catch (Exception e) {
            log.warn("FileWatchService created error, can‘t load the certificate dynamically");
        }
    }

    return true;
}

说明：

1. KVConfigManager.load加载原来的key-value文件到内存中
2. 初始化NettyRemotingServer
3. 初始化nettyRomote线程池，默认8个
4. 注册requestProcessor，默认为DefaultRequestProcessor，用来处理netty接收到的信息
5. 启动定时线程，延迟5秒执行，每隔10s扫描未活动的Broker，这个是否用于解决问题2
6. 启动定时线程，延迟1秒执行，每隔10min打印出所有k-v

NamesrvController.start()

启动netty server

public void start() throws Exception {
    this.remotingServer.start();

    if (this.fileWatchService != null) {
        this.fileWatchService.start();
    }
}

启动Netty服务端

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());
            }
        });

    ServerBootstrap childHandler =
        this.serverBootstrap.group(this.eventLoopGroupBoss, this.eventLoopGroupSelector)
        .channel(useEpoll() ? EpollServerSocketChannel.class : NioServerSocketChannel.class)
        .option(ChannelOption.SO_BACKLOG, 1024)
        .option(ChannelOption.SO_REUSEADDR, true)
        .option(ChannelOption.SO_KEEPALIVE, false)
        .childOption(ChannelOption.TCP_NODELAY, true)
        .childOption(ChannelOption.SO_SNDBUF, nettyServerConfig.getServerSocketSndBufSize())
        .childOption(ChannelOption.SO_RCVBUF, nettyServerConfig.getServerSocketRcvBufSize())
        .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,
                             new HandshakeHandler(TlsSystemConfig.tlsMode))
                    .addLast(defaultEventExecutorGroup,
                             new NettyEncoder(),
                             new NettyDecoder(),
                             new IdleStateHandler(0, 0, nettyServerConfig.getServerChannelMaxIdleTimeSeconds()),
                             new NettyConnectManageHandler(),
                             new NettyServerHandler()
                            );
            }
        });

    if (nettyServerConfig.isServerPooledByteBufAllocatorEnable()) {
        childHandler.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
    }

    try {
        ChannelFuture sync = this.serverBootstrap.bind().sync();
        InetSocketAddress addr = (InetSocketAddress) sync.channel().localAddress();
        this.port = addr.getPort();
    } catch (InterruptedException e1) {
        throw new RuntimeException("this.serverBootstrap.bind().sync() InterruptedException", e1);
    }

    if (this.channelEventListener != null) {
        this.nettyEventExecutor.start();
    }

    this.timer.scheduleAtFixedRate(new TimerTask() {

        @Override
            public void run() {
            try {
                NettyRemotingServer.this.scanResponseTable();
            } catch (Throwable e) {
                log.error("scanResponseTable exception", e);
            }
        }
    }, 1000 * 3, 1000);
}

对于RocketMQ使用Netty进行集群之间的通信，后面会有单独章节用于讲解该模块：RocketMQ-remoting。

NameServer处理信息

netty收到的所有消息都是org.apache.rocketmq.namesrv.processor.DefaultRequestProcessor.processRequest处理的,根据不同的RequestCode执行不同的操作。

public RemotingCommand processRequest(ChannelHandlerContext ctx,
                                      RemotingCommand request) throws RemotingCommandException {

    if (ctx != null) {
        log.debug("receive request, {} {} {}",
                  request.getCode(),
                  RemotingHelper.parseChannelRemoteAddr(ctx.channel()),
                  request);
    }


    switch (request.getCode()) {
        case RequestCode.PUT_KV_CONFIG:
        return this.putKVConfig(ctx, request);
        case RequestCode.GET_KV_CONFIG:
        return this.getKVConfig(ctx, request);
        case RequestCode.DELETE_KV_CONFIG:
        return this.deleteKVConfig(ctx, request);
        case RequestCode.QUERY_DATA_VERSION:
        return queryBrokerTopicConfig(ctx, request);
        case RequestCode.REGISTER_BROKER:// 注册borker信息
        // 获取Broker的版本信息
        Version brokerVersion = MQVersion.value2Version(request.getVersion());
        if (brokerVersion.ordinal() >= MQVersion.Version.V3_0_11.ordinal()) {
            // 3.0.11版本后的处理方式
            return this.registerBrokerWithFilterServer(ctx, request);
        } else {
            // 3.0.11版本之前的处理方式
            return this.registerBroker(ctx, request);
        }
        case RequestCode.UNREGISTER_BROKER:
        return this.unregisterBroker(ctx, request);// 取消注册broker
        case RequestCode.GET_ROUTEINTO_BY_TOPIC:
        return this.getRouteInfoByTopic(ctx, request);// 根据topic获取路由信息，在producer发送消息和consumer在pull消息的时候的时候会从nameServer 中获取
        case RequestCode.GET_BROKER_CLUSTER_INFO:
        return this.getBrokerClusterInfo(ctx, request);
        case RequestCode.WIPE_WRITE_PERM_OF_BROKER:
        return this.wipeWritePermOfBroker(ctx, request);
        case RequestCode.GET_ALL_TOPIC_LIST_FROM_NAMESERVER:
        return getAllTopicListFromNameserver(ctx, request);
        case RequestCode.DELETE_TOPIC_IN_NAMESRV:
        return deleteTopicInNamesrv(ctx, request);
        case RequestCode.GET_KVLIST_BY_NAMESPACE:
        return this.getKVListByNamespace(ctx, request);
        case RequestCode.GET_TOPICS_BY_CLUSTER:
        return this.getTopicsByCluster(ctx, request);
        case RequestCode.GET_SYSTEM_TOPIC_LIST_FROM_NS:
        return this.getSystemTopicListFromNs(ctx, request);
        case RequestCode.GET_UNIT_TOPIC_LIST:
        return this.getUnitTopicList(ctx, request);
        case RequestCode.GET_HAS_UNIT_SUB_TOPIC_LIST:
        return this.getHasUnitSubTopicList(ctx, request);
        case RequestCode.GET_HAS_UNIT_SUB_UNUNIT_TOPIC_LIST:
        return this.getHasUnitSubUnUnitTopicList(ctx, request);
        case RequestCode.UPDATE_NAMESRV_CONFIG:
        return this.updateConfig(ctx, request);
        case RequestCode.GET_NAMESRV_CONFIG:
        return this.getConfig(ctx, request);
        default:
        break;
    }
    return null;
}

注册Broker

case RequestCode.REGISTER_BROKER:// 注册borker信息
    // 获取Broker的版本信息
    Version brokerVersion = MQVersion.value2Version(request.getVersion());
    if (brokerVersion.ordinal() >= MQVersion.Version.V3_0_11.ordinal()) {
        // 3.0.11版本后的处理方式
        return this.registerBrokerWithFilterServer(ctx, request);
    } else {
        // 3.0.11版本之前的处理方式
        return this.registerBroker(ctx, request);
    }

org.apache.rocketmq.namesrv.processor.DefaultRequestProcessor#registerBrokerWithFilterServer

public RemotingCommand registerBrokerWithFilterServer(ChannelHandlerContext ctx, RemotingCommand request)
    throws RemotingCommandException {
    // 解析请求，获取RequestHeader
    final RemotingCommand response = RemotingCommand.createResponseCommand(RegisterBrokerResponseHeader.class);
    final RegisterBrokerResponseHeader responseHeader = (RegisterBrokerResponseHeader) response.readCustomHeader();
    final RegisterBrokerRequestHeader requestHeader =
        (RegisterBrokerRequestHeader) request.decodeCommandCustomHeader(RegisterBrokerRequestHeader.class);

    if (!checksum(ctx, request, requestHeader)) {
        response.setCode(ResponseCode.SYSTEM_ERROR);
        response.setRemark("crc32 not match");
        return response;
    }

    RegisterBrokerBody registerBrokerBody = new RegisterBrokerBody();

    // 获取RegisterBrokerBody
    if (request.getBody() != null) {
        try {
            registerBrokerBody = RegisterBrokerBody.decode(request.getBody(), requestHeader.isCompressed());
        } catch (Exception e) {
            throw new RemotingCommandException("Failed to decode RegisterBrokerBody", e);
        }
    } else {
        registerBrokerBody.getTopicConfigSerializeWrapper().getDataVersion().setCounter(new AtomicLong(0));
        registerBrokerBody.getTopicConfigSerializeWrapper().getDataVersion().setTimestamp(0);
    }

    // 注册Broker
    RegisterBrokerResult result = this.namesrvController.getRouteInfoManager().registerBroker(
        requestHeader.getClusterName(),
        requestHeader.getBrokerAddr(),
        requestHeader.getBrokerName(),
        requestHeader.getBrokerId(),
        requestHeader.getHaServerAddr(),
        registerBrokerBody.getTopicConfigSerializeWrapper(),
        registerBrokerBody.getFilterServerList(),
        ctx.channel());

    // 设置响应结果
    responseHeader.setHaServerAddr(result.getHaServerAddr());
    responseHeader.setMasterAddr(result.getMasterAddr());

    byte[] jsonValue = this.namesrvController.getKvConfigManager().getKVListByNamespace(NamesrvUtil.NAMESPACE_ORDER_TOPIC_CONFIG);
    response.setBody(jsonValue);

    response.setCode(ResponseCode.SUCCESS);
    response.setRemark(null);
    return response;
}

对于netty通信这块这里不过多深究，我们知道由Broker发送过来的消息带有以下这些消息：

RouteInfoManager

org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager

结构说明

//topic队列信息
private final HashMap<String/* topic */, List<QueueData>> topicQueueTable;
//broker信息
private final HashMap<String/* brokerName */, BrokerData> brokerAddrTable;
//cluster信息
private final HashMap<String/* clusterName */, Set<String/* brokerName */>> clusterAddrTable;
//存活的broker信息
private final HashMap<String/* brokerAddr */, BrokerLiveInfo> brokerLiveTable;
//broker filter
private final HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;

RouteInfoManager为管理Broker所注册的Topic路由信息和集群的信息。其实就是维护了相对应的几个Map

注册Broker：registerBroker

org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager#registerBroker

public RegisterBrokerResult registerBroker(
    final String clusterName,
    final String brokerAddr,
    final String brokerName,
    final long brokerId,
    final String haServerAddr,
    final TopicConfigSerializeWrapper topicConfigWrapper,
    final List<String> filterServerList,
    final Channel channel) {
    RegisterBrokerResult result = new RegisterBrokerResult();
    try {
        try {
            // 获取写锁
            this.lock.writeLock().lockInterruptibly();
            // 获取该Cluster下的所有Broker,并添加该Broker
            Set<String> brokerNames = this.clusterAddrTable.get(clusterName);
            if (null == brokerNames) {
                brokerNames = new HashSet<String>();
                this.clusterAddrTable.put(clusterName, brokerNames);
            }
            brokerNames.add(brokerName);
            // 是否第一次注册，标志位
            boolean registerFirst = false;
            // 获取该BrokerName的BrokerData信息
            BrokerData brokerData = this.brokerAddrTable.get(brokerName);
            if (null == brokerData) {
                // 为空，第一次注册，构建信息存入
                registerFirst = true;
                brokerData = new BrokerData(clusterName, brokerName, new HashMap<Long, String>());
                this.brokerAddrTable.put(brokerName, brokerData);
            }
            // 存入brokerAddrs信息，若oldAddr为null则为第一次put
            String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);
            registerFirst = registerFirst || (null == oldAddr);
            // 若TopicConfigSerializeWrapper不为空，该类为TopicConfig信息的包装类，方便传输
            // 且该broker为主，即 brokerId==0
            if (null != topicConfigWrapper
                && MixAll.MASTER_ID == brokerId) {
                // 判断Broker的TopicConfig信息是否改变||第一注册Broker信息
                if (this.isBrokerTopicConfigChanged(brokerAddr, topicConfigWrapper.getDataVersion()) || registerFirst) {
                    ConcurrentMap<String, TopicConfig> tcTable = topicConfigWrapper.getTopicConfigTable();
                    if (tcTable != null) {
                        for (Map.Entry<String, TopicConfig> entry : tcTable.entrySet()) {
                            // 填充topicQueueTable
                            this.createAndUpdateQueueData(brokerName, entry.getValue());
                        }
                    }
                }
            }
            // 填充brokerLiveTable
            BrokerLiveInfo prevBrokerLiveInfo = this.brokerLiveTable.put(brokerAddr,
                                                                         new BrokerLiveInfo(
                                                                             System.currentTimeMillis(),
                                                                             topicConfigWrapper.getDataVersion(),
                                                                             channel,
                                                                             haServerAddr));
            // 第一次注册
            if (null == prevBrokerLiveInfo) {
                log.info("new broker registered, {} HAServer: {}", brokerAddr, haServerAddr);
            }

            if (filterServerList != null) {
                if (filterServerList.isEmpty()) {
                    this.filterServerTable.remove(brokerAddr);
                } else {
                    this.filterServerTable.put(brokerAddr, filterServerList);
                }
            }
            // 备机处理，获取Master地址，构建返回结果
            if (MixAll.MASTER_ID != brokerId) {
                String masterAddr = brokerData.getBrokerAddrs().get(MixAll.MASTER_ID);
                if (masterAddr != null) {
                    BrokerLiveInfo brokerLiveInfo = this.brokerLiveTable.get(masterAddr);
                    if (brokerLiveInfo != null) {
                        result.setHaServerAddr(brokerLiveInfo.getHaServerAddr());
                        result.setMasterAddr(masterAddr);
                    }
                }
            }
        } finally {
            // 释放写锁
            this.lock.writeLock().unlock();
        }
    } catch (Exception e) {
        log.error("registerBroker Exception", e);
    }

    return result;
}

说明：

1. 填充clusterAddrTable
2. 填充brokerAddrTable
3. 填充topicQueueTable
4. 填充brokerLiveTable
5. 填充filterServerTable

自此整个Broker的注册过程完结，其实就是填充这5个Map的过程。问题1答案也浮出水面。

如何处理未存活的Broker

Broker未存活的判断

1. Broker和Namesrv的Channel通道发生close、excepiton、idle事件，namesrv端将调用onChannelDestroy进行处理
2. Namesrv将启动一个定时线程每隔10s扫描已上报的brokerLiveTable中所有Broker信息是否已超时上报，默认超时为120s，若超时，调用onChannelDestroy进行处理。

BrokerHousekeepingService

org.apache.rocketmq.namesrv.routeinfo.BrokerHousekeepingService implement ChannelEventListener

在发生Channel Event时将回调该方法：

public class BrokerHousekeepingService implements ChannelEventListener {
    private static final InternalLogger log = InternalLoggerFactory.getLogger(LoggerName.NAMESRV_LOGGER_NAME);
    private final NamesrvController namesrvController;

    public BrokerHousekeepingService(NamesrvController namesrvController) {
        this.namesrvController = namesrvController;
    }

    @Override
    public void onChannelConnect(String remoteAddr, Channel channel) {
    }

    @Override
    public void onChannelClose(String remoteAddr, Channel channel) {
        this.namesrvController.getRouteInfoManager().onChannelDestroy(remoteAddr, channel);
    }

    @Override
    public void onChannelException(String remoteAddr, Channel channel) {
        this.namesrvController.getRouteInfoManager().onChannelDestroy(remoteAddr, channel);
    }

    @Override
    public void onChannelIdle(String remoteAddr, Channel channel) {
        this.namesrvController.getRouteInfoManager().onChannelDestroy(remoteAddr, channel);
    }
}

定时线程scanNotActiveBroker

org.apache.rocketmq.namesrv.NamesrvController#initialize

public boolean initialize() {
    // ...省略代码
    //5.    启动定时线程，延迟5秒执行，每隔10s判断broker是否依然存活
    this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

        @Override
            public void run() {
            NamesrvController.this.routeInfoManager.scanNotActiveBroker();
        }
    }, 5, 10, TimeUnit.SECONDS);
    // ...省略代码
    return true;
}

org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager#scanNotActiveBroker

public void scanNotActiveBroker() {
    Iterator<Entry<String, BrokerLiveInfo>> it = this.brokerLiveTable.entrySet().iterator();
    while (it.hasNext()) {
        Entry<String, BrokerLiveInfo> next = it.next();
        long last = next.getValue().getLastUpdateTimestamp();
        if ((last + BROKER_CHANNEL_EXPIRED_TIME) < System.currentTimeMillis()) {
            RemotingUtil.closeChannel(next.getValue().getChannel());
            it.remove();
            log.warn("The broker channel expired, {} {}ms", next.getKey(), BROKER_CHANNEL_EXPIRED_TIME);
            this.onChannelDestroy(next.getKey(), next.getValue().getChannel());
        }
    }
}

若超时，也是调用onChannelDestroy方法进行移除路由信息

RouteInfoManager#onChannelDestroy

org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager#onChannelDestroy

public void onChannelDestroy(String remoteAddr, Channel channel) {
    // 获取BrokerAddr,注意remoteAddr是Broker与netty连接的地址，并不是Broker nettyServer所监听的地址
    String brokerAddrFound = null;
    if (channel != null) {
        try {
            try {
                this.lock.readLock().lockInterruptibly();
                Iterator<Entry<String, BrokerLiveInfo>> itBrokerLiveTable =
                    this.brokerLiveTable.entrySet().iterator();
                while (itBrokerLiveTable.hasNext()) {
                    Entry<String, BrokerLiveInfo> entry = itBrokerLiveTable.next();
                    if (entry.getValue().getChannel() == channel) {
                        brokerAddrFound = entry.getKey();
                        break;
                    }
                }
            } finally {
                this.lock.readLock().unlock();
            }
        } catch (Exception e) {
            log.error("onChannelDestroy Exception", e);
        }
    }

    if (null == brokerAddrFound) {
        brokerAddrFound = remoteAddr;
    } else {
        log.info("the broker‘s channel destroyed, {}, clean it‘s data structure at once", brokerAddrFound);
    }

    if (brokerAddrFound != null && brokerAddrFound.length() > 0) {

        try {
            try {
                this.lock.writeLock().lockInterruptibly();
                // 1.移除brokerLiveTable
                this.brokerLiveTable.remove(brokerAddrFound);
                // 2.移除filterServerTable
                this.filterServerTable.remove(brokerAddrFound);
                String brokerNameFound = null;
                boolean removeBrokerName = false;
                // 3.移除brokerAddrTable
                Iterator<Entry<String, BrokerData>> itBrokerAddrTable =
                    this.brokerAddrTable.entrySet().iterator();
                while (itBrokerAddrTable.hasNext() && (null == brokerNameFound)) {
                    BrokerData brokerData = itBrokerAddrTable.next().getValue();

                    Iterator<Entry<Long, String>> it = brokerData.getBrokerAddrs().entrySet().iterator();
                    while (it.hasNext()) {
                        Entry<Long, String> entry = it.next();
                        Long brokerId = entry.getKey();
                        String brokerAddr = entry.getValue();
                        if (brokerAddr.equals(brokerAddrFound)) {
                            brokerNameFound = brokerData.getBrokerName();
                            it.remove();
                            log.info("remove brokerAddr[{}, {}] from brokerAddrTable, because channel destroyed",
                                     brokerId, brokerAddr);
                            break;
                        }
                    }

                    if (brokerData.getBrokerAddrs().isEmpty()) {
                        removeBrokerName = true;
                        itBrokerAddrTable.remove();
                        log.info("remove brokerName[{}] from brokerAddrTable, because channel destroyed",
                                 brokerData.getBrokerName());
                    }
                }
                // 4.移除clusterAddrTable
                if (brokerNameFound != null && removeBrokerName) {
                    Iterator<Entry<String, Set<String>>> it = this.clusterAddrTable.entrySet().iterator();
                    while (it.hasNext()) {
                        Entry<String, Set<String>> entry = it.next();
                        String clusterName = entry.getKey();
                        Set<String> brokerNames = entry.getValue();
                        boolean removed = brokerNames.remove(brokerNameFound);
                        if (removed) {
                            log.info("remove brokerName[{}], clusterName[{}] from clusterAddrTable, because channel destroyed",
                                     brokerNameFound, clusterName);

                            if (brokerNames.isEmpty()) {
                                log.info("remove the clusterName[{}] from clusterAddrTable, because channel destroyed and no broker in this cluster",
                                         clusterName);
                                it.remove();
                            }

                            break;
                        }
                    }
                }
                // 5.移除topicQueueTable
                if (removeBrokerName) {
                    Iterator<Entry<String, List<QueueData>>> itTopicQueueTable =
                        this.topicQueueTable.entrySet().iterator();
                    while (itTopicQueueTable.hasNext()) {
                        Entry<String, List<QueueData>> entry = itTopicQueueTable.next();
                        String topic = entry.getKey();
                        List<QueueData> queueDataList = entry.getValue();

                        Iterator<QueueData> itQueueData = queueDataList.iterator();
                        while (itQueueData.hasNext()) {
                            QueueData queueData = itQueueData.next();
                            if (queueData.getBrokerName().equals(brokerNameFound)) {
                                itQueueData.remove();
                                log.info("remove topic[{} {}], from topicQueueTable, because channel destroyed",
                                         topic, queueData);
                            }
                        }

                        if (queueDataList.isEmpty()) {
                            itTopicQueueTable.remove();
                            log.info("remove topic[{}] all queue, from topicQueueTable, because channel destroyed",
                                     topic);
                        }
                    }
                }
            } finally {
                this.lock.writeLock().unlock();
            }
        } catch (Exception e) {
            log.error("onChannelDestroy Exception", e);
        }
    }
}

日志

20:18:32.951 [NettyServerCodecThread_1] WARN  RocketmqRemoting - NETTY SERVER PIPELINE: exceptionCaught 127.0.0.1:8078
20:18:32.960 [NettyServerCodecThread_1] WARN  RocketmqRemoting - NETTY SERVER PIPELINE: exceptionCaught exception.
java.io.IOException: 远程主机强迫关闭了一个现有的连接。
    at sun.nio.ch.SocketDispatcher.read0(Native Method) ~[na:1.8.0_111]
    at sun.nio.ch.SocketDispatcher.read(SocketDispatcher.java:43) ~[na:1.8.0_111]
    at sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:223) ~[na:1.8.0_111]
    at sun.nio.ch.IOUtil.read(IOUtil.java:192) ~[na:1.8.0_111]
    at sun.nio.ch.SocketChannelImpl.read(SocketChannelImpl.java:380) ~[na:1.8.0_111]
    at io.netty.buffer.PooledUnsafeDirectByteBuf.setBytes(PooledUnsafeDirectByteBuf.java:221) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.buffer.AbstractByteBuf.writeBytes(AbstractByteBuf.java:899) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.channel.socket.nio.NioSocketChannel.doReadBytes(NioSocketChannel.java:275) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:119) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:652) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:575) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:489) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:451) ~[netty-all-4.0.42.Final.jar:4.0.42.Final]
    at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:140) [netty-all-4.0.42.Final.jar:4.0.42.Final]
    at java.lang.Thread.run(Thread.java:745) [na:1.8.0_111]
20:18:32.963 [NettyServerNIOSelector_3_1] INFO  RocketmqRemoting - closeChannel: close the connection to remote address[127.0.0.1:8078] result: true
20:18:32.963 [NettyServerCodecThread_1] INFO  RocketmqRemoting - NETTY SERVER PIPELINE: channelInactive, the channel[127.0.0.1:8078]
20:18:32.963 [NettyServerCodecThread_1] INFO  RocketmqRemoting - NETTY SERVER PIPELINE: channelUnregistered, the channel[127.0.0.1:8078]
20:19:19.394 [NettyEventExecutor] INFO  RocketmqNamesrv - the broker‘s channel destroyed, 192.168.72.1:10911, clean it‘s data structure at once
20:20:29.565 [NettyEventExecutor] INFO  RocketmqNamesrv - remove brokerAddr[0, 192.168.72.1:10911] from brokerAddrTable, because channel destroyed
20:20:50.713 [NettyEventExecutor] INFO  RocketmqNamesrv - remove brokerName[broker-a] from brokerAddrTable, because channel destroyed
20:21:34.787 [NettyEventExecutor] INFO  RocketmqNamesrv - remove brokerName[broker-a], clusterName[DefaultCluster] from clusterAddrTable, because channel destroyed
20:21:36.033 [NettyEventExecutor] INFO  RocketmqNamesrv - remove the clusterName[DefaultCluster] from clusterAddrTable, because channel destroyed and no broker in this cluster
20:21:56.126 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[broker-a QueueData [brokerName=broker-a, readQueueNums=1, writeQueueNums=1, perm=7, topicSynFlag=0]], from topicQueueTable, because channel destroyed
20:22:02.100 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[broker-a] all queue, from topicQueueTable, because channel destroyed
20:22:07.553 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[SELF_TEST_TOPIC QueueData [brokerName=broker-a, readQueueNums=1, writeQueueNums=1, perm=6, topicSynFlag=0]], from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[SELF_TEST_TOPIC] all queue, from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[TBW102 QueueData [brokerName=broker-a, readQueueNums=8, writeQueueNums=8, perm=7, topicSynFlag=0]], from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[TBW102] all queue, from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[BenchmarkTest QueueData [brokerName=broker-a, readQueueNums=1024, writeQueueNums=1024, perm=6, topicSynFlag=0]], from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[BenchmarkTest] all queue, from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[DefaultCluster QueueData [brokerName=broker-a, readQueueNums=16, writeQueueNums=16, perm=7, topicSynFlag=0]], from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[DefaultCluster] all queue, from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[OFFSET_MOVED_EVENT QueueData [brokerName=broker-a, readQueueNums=1, writeQueueNums=1, perm=6, topicSynFlag=0]], from topicQueueTable, because channel destroyed
20:22:07.554 [NettyEventExecutor] INFO  RocketmqNamesrv - remove topic[OFFSET_MOVED_EVENT] all queue, from topicQueueTable, because channel destroyed

说明：

实质就是移除RouteInfoManager中的5个Map

总结

NameSrv集群是一个无状态节点，维护Broker注册的Topic信息，将向生产者和消费者提供Topic路由信息。
对于提出的两个问题：
问题1：RouteInfoManager中有5个Map用于存储Broker的路由信息。
问题2：Namesrv中两种方式来处理Broker异常的情况，一是使用netty的channel事件机制实现不同事件的回调处理方法，该方式主要为处理channel通道发生异常情况。二是使用一个定时线程检测最新上报时间是否已超时（120s），若超时则认为该Broker断掉。