NameServer架構設計

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Broker消息服務器在啟動時向所有NameServer注冊,消息生產者(Producer)在發送消息之前先從NameServer獲取Broker服務器地址列表,然后根據負載均衡算法從列表中選擇一臺服務器進行消息發送。NameServer與每臺Broker保持長連接,并間隔10s檢測Broker是否存活,如果檢測到Broker宕機,則從路由注冊表中將其移除。

但是路由變化不會馬上通知消息生產者,為什么要這樣設計呢?
這是為了降低NameServer實現的復雜性,在消息發送端提供容錯機制來保證消息發送的高可用性。

NameServer本身的高可用可通過部署多臺NameServer服務器來實現,但彼此之間互不通信,也就是NameServer服務器之間在某一時刻的數據并不會完全相同,但這對消息發送不會造成任何影響,這也是RocketMQ NameServer設計的一個亮點,RocketMQ NameServer設計追求簡單高效。

NameServer啟動流程

NameServer啟動類: org.apache.rocketmq.namesrv.NamesrvStartup
Step1: 首先來解析配置文件,需要填充NamesrvConfig、NettyServerConfig屬性值。

            final NamesrvConfig namesrvConfig = new NamesrvConfig();
            final NettyServerConfig nettyServerConfig = new NettyServerConfig();
            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);
                    MixAll.properties2Object(properties, namesrvConfig);
                    MixAll.properties2Object(properties, nettyServerConfig);

                    namesrvConfig.setConfigStorePath(file);

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

            if (commandLine.hasOption('p')) {
                MixAll.printObjectProperties(null, namesrvConfig);
                MixAll.printObjectProperties(null, nettyServerConfig);
                System.exit(0);
            }

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

從代碼我們可以知道先創建NamesrvConfig(NameServer業務參數)、NettyServerConfig(NameServer網絡參數),然后在解析啟動時把指定的配置文件或啟動命令中的選項值,填充到namesrvConfig,nettyServerConfig對象。
參數來源有如下兩種方式:
1、-c configFile通過-c命令指定配置文件的路徑
2、使用"--屬性名 屬性值",例如--listenPort 9876

NameServerConfig屬性

    private String rocketmqHome = System.getProperty(MixAll.ROCKETMQ_HOME_PROPERTY, System.getenv(MixAll.ROCKETMQ_HOME_ENV));
    private String kvConfigPath = System.getProperty("user.home") + File.separator + "namesrv" + File.separator + "kvConfig.json";
    private String configStorePath = System.getProperty("user.home") + File.separator + "namesrv" + File.separator + "namesrv.properties";
    private String productEnvName = "center";
    private boolean clusterTest = false;
    private boolean orderMessageEnable = false;

• rocketmqhome: rocketmq主目錄,可以通過-Drocketmq.home.dir=path或通過設置環境變量ROCKETMQ_HOME來配置RocketMQ的主目錄。
• kvConfigPath: NameServer存儲KV配置屬性的持久化路徑。
• configStorePath: nameServer默認配置文件路徑,不生效。nameServer啟動時如果要通過配置文件配置NameServer啟動屬性的話,請使用-c選項。
• orderMessageEnable: 是否支持順序消息,默認是不支持

NettyServerConfig屬性

    private int listenPort = 8888;
    private int serverWorkerThreads = 8;
    private int serverCallbackExecutorThreads = 0;
    private int serverSelectorThreads = 3;
    private int serverOnewaySemaphoreValue = 256;
    private int serverAsyncSemaphoreValue = 64;
    private int serverChannelMaxIdleTimeSeconds = 120;
    private int serverSocketSndBufSize = NettySystemConfig.socketSndbufSize;
    private int serverSocketRcvBufSize = NettySystemConfig.socketRcvbufSize;
    private boolean serverPooledByteBufAllocatorEnable = true;
    private boolean useEpollNativeSelector = false;

• listenPort: NameServer監聽端口,該值默認會被初始化9876。
• serverWorkerThreads: Netty業務線程池線程個數。
• serverCallbackExecutorThreads: Netty public 任務線程池線程個數,Netty網絡設計,根據業務類型會常見不同的線程池,比如處理消息發送、消息消費、心跳檢測等等。如果該業務類型(RequestCode)未注冊線程池,則由public線程池執行。
• serverSelectorThreads:IO線程池線程個數,主要是NameServer、Broker端解析請求、返回相應的線程個數,這類線程主要是處理網絡請求的,解析請求包,然后轉發到各個業務線程池完成具體的業務操作,然后將結果返回調用方。
• serverOnewaySemaphoreValue: send oneway消息請求并發度(Broker端參數)。
• serverAsyncSemaphoreValue: 異步消息發送最大并發度(Broker端參數)。
• serverChannelMaxIdleTimeSeconds: 網絡連接最大空閑時間,默認120s。如果連接空閑時間超過該參數設置的值,連接將被關閉。
• serverSocketSndBufSize: 網絡socket發送緩存區大小,默認64k。
• serverSocketRecBufSize: 網絡socket接收緩存區大小,默認64k。
• serverPooledByteBufAllocatorEnable: ByteBuffer是否開啟緩存,建議開啟。
• useEpollNativeSelector: 是否啟用Epoll IO模型,Linux環境建議開啟。

在啟動NameServer時,可以先使用./mqnameserver -c configFile -p 打印當前加載的配置屬性。

Step2: 根據啟動屬性創建NamesrvController實例,并初始化該實例,NamesrvController實例為NameServer核心控制器。

NamesrvController#initialize代碼片段

    public boolean initialize() {

        this.kvConfigManager.load();

        this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.brokerHousekeepingService);

        this.remotingExecutor =
            Executors.newFixedThreadPool(nettyServerConfig.getServerWorkerThreads(), new ThreadFactoryImpl("RemotingExecutorThread_"));

        this.registerProcessor();

        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

            @Override
            public void run() {
                NamesrvController.this.routeInfoManager.scanNotActiveBroker();
            }
        }, 5, 10, TimeUnit.SECONDS);

        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

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

        return true;
    }

加載KV配置,創建NettyServer網絡處理對象,然后開啟兩個定時任務,在RocketMQ中此類定時任務統稱為心跳檢測。

• 定時任務1: NameServer每隔10s掃描一次Broker,移除處于不激活狀態的Broker。
• 定時任務2: NameServer每隔十分鐘打印一次KV配置。

Step3: 注冊JVM鉤子函數并啟動服務器,以便監聽Broker、消息生產者的網絡請求。

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

            controller.start();

NameServer路由注冊、故障剔除

NameServer主要作用是為消息生產者和消息消費者提供關于主題Topic的路由信息,那么NameServer需要存儲路由的基礎信息,還要能夠管理Broker節點,包括路由注冊、路由刪除等功能。

路由元信息

NameServer路由實現類: org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager,在了解路由注冊之前,我們首先看一下NameServer到底存儲哪些信息。

    private final HashMap<String/* topic */, List<QueueData>> topicQueueTable;
    private final HashMap<String/* brokerName */, BrokerData> brokerAddrTable;
    private final HashMap<String/* clusterName */, Set<String/* brokerName */>> clusterAddrTable;
    private final HashMap<String/* brokerAddr */, BrokerLiveInfo> brokerLiveTable;
    private final HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;

• topicQueueTable: Topic消息隊列路由信息,消息發送時根據路由表進行負載均衡。
• brokerAddrTable: Broker基礎信息,包含BrokerName、所屬集群名稱、主備Broker地址。
• clusterAddrTable: Broker集群信息,存儲集群中所有Broker名稱。
• brokerLiveTable: Broker狀態信息。NameServer每次收到心跳包時會替換該信息。
• filterServerTable: Broker上的FilterServer列表,用于類模式消息過濾。

RocketMQ基于訂閱發布機制,一個Topic擁有多個消息隊列,一個Broker為每一主題默認創建4個讀隊列4個寫隊列。多個Broker組成一個集群,BrokerName由相同的多臺Broker組成Master-Slave架構,brokerId為0表示Master,大于0表示Slave。BrokerLiveInfo中的lastUpdateTimestamp存儲上次收到Broker心跳包的時間。

QueueData

    private String brokerName;
    private int readQueueNums;
    private int writeQueueNums;
    private int perm;
    private int topicSynFlag;

BrokerData

    private String cluster;
    private String brokerName;
    // brokerId為0表示Master,大于0表示Slave
    private HashMap<Long/* brokerId */, String/* broker address */> brokerAddrs;

BrokerLiveInfo

    private long lastUpdateTimestamp;
    private DataVersion dataVersion;
    private Channel channel;
    private String haServerAddr;

路由注冊

RocketMQ路由注冊是通過Broker與NameServer的心跳功能實現的。Broker啟動時向集群中所有的NameServer發送心跳語句,每隔30秒向集群中所有NameServer發送心跳包,NameServer收到Broker心跳包時會更新brokerLiveTable緩存中BrokerLiveInfo的lastUpdateTimestamp,然后NameServer每隔10秒掃描brokerLiveTable,如果連續120s沒有收到心跳包,NameServer將移除該Broker的路由信息同時關閉Socket連接。

Broker發送心跳包

Broker發送心跳包的核心代碼如下所示。

Broker端心跳包發送(BrokerController#start)

        this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                try {
                    BrokerController.this.registerBrokerAll(true, false);
                } catch (Throwable e) {
                    log.error("registerBrokerAll Exception", e);
                }
            }
        }, 1000 * 10, 1000 * 30, TimeUnit.MILLISECONDS);

BrokerOuterAPI#registerBrokerAll

        List<String> nameServerAddressList = this.remotingClient.getNameServerAddressList();
        if (nameServerAddressList != null) {
            for (String namesrvAddr : nameServerAddressList) {// 遍歷所有NameServer列表
                try {
                    RegisterBrokerResult result = this.registerBroker(namesrvAddr, clusterName, brokerAddr, brokerName, brokerId,
                        haServerAddr, topicConfigWrapper, filterServerList, oneway, timeoutMills);// 分別向NameServer注冊
                    if (result != null) {
                        registerBrokerResult = result;
                    }

                    log.info("register broker to name server {} OK", namesrvAddr);
                } catch (Exception e) {
                    log.warn("registerBroker Exception, {}", namesrvAddr, e);
                }
            }
        }

BrokerOuteAPI#registerBroker(網絡發送代碼)

        RegisterBrokerRequestHeader requestHeader = new RegisterBrokerRequestHeader();
        requestHeader.setBrokerAddr(brokerAddr);
        requestHeader.setBrokerId(brokerId);
        requestHeader.setBrokerName(brokerName);
        requestHeader.setClusterName(clusterName);
        requestHeader.setHaServerAddr(haServerAddr);
        RemotingCommand request = RemotingCommand.createRequestCommand(RequestCode.REGISTER_BROKER, requestHeader);

        RegisterBrokerBody requestBody = new RegisterBrokerBody();
        requestBody.setTopicConfigSerializeWrapper(topicConfigWrapper);
        requestBody.setFilterServerList(filterServerList);
        request.setBody(requestBody.encode());

        if (oneway) {
            try {
                this.remotingClient.invokeOneway(namesrvAddr, request, timeoutMills);
            } catch (RemotingTooMuchRequestException e) {
                // Ignore
            }
            return null;
        }

        RemotingCommand response = this.remotingClient.invokeSync(namesrvAddr, request, timeoutMills);

發送心跳包具體邏輯,首先封裝請求包頭(Header)。

• brokerAddr: broker地址。
• brokerId: brokerId,0: Master ; 大于0: Slave。
• brokerName: broker名稱。
• clusterName: 集群名稱。
• haServerAddr: master地址,初次請求時該值為空,slave向Nameserver注冊后返回。
• requestBody:
  • filterServerList: 消息過濾服務器列表。
  • topicConfigWapper: 主題配置,topicConfigWrapper內部封裝的是TopicConfigManager中的topicConfigTable,內部存儲的是Broker啟動時默認的一些Topic,MixAll.SELF_TEST_TOPIC、MixAll.DEFAULT_TOPICC(AutoCreateTopicEnable=true)、MixAll.BENCHMARK_TOPIC、MixAll.OFFSET_MOVED_EVENT、BrokerConfig#brokerClusterName、BrokerConfig#brokerName。Broker中Topic默認存儲在${Rocket_Home}/store/config/topics.json中。

NameServer處理心跳包

org.apache.rocketmq.namesrv.processor.DefaultRequestProcessor網絡處理器解析請求類型,如果請求類型為RequestCode.REGISTER_BROKER,則請求最終轉發到RouteInfoManager#registerBroker。

Step1: 路由注冊需要加寫鎖,防止并發修改RouteInfoManager中的路由表。首先判斷Broker所屬集群是否存在,如果不存在,則創建,然后將broker名加入到集群Broker集合中。

RouteInfoManager#registerBroker clusterAddrTable維護

                this.lock.writeLock().lockInterruptibly();
                Set<String> brokerNames = this.clusterAddrTable.get(clusterName);
                if (null == brokerNames) {
                    brokerNames = new HashSet<String>();
                    this.clusterAddrTable.put(clusterName, brokerNames);
                }
                brokerNames.add(brokerName);

Step2: 維護BrokerData信息,首先從brokerAddrTable根據BrokerName嘗試獲取Broker信息,如果不存在,則新建BrokerData并放入brokerAddrTable,registerFirst設置為true;如果存在,直接替換原先的,registerFirst設置為false,表示非第一次注冊

RouteInfoManager#registerBroker brokerAddrTable維護

                BrokerData brokerData = this.brokerAddrTable.get(brokerName);
                if (null == brokerData) {
                    registerFirst = true;
                    brokerData = new BrokerData(clusterName, brokerName, new HashMap<Long, String>());
                    this.brokerAddrTable.put(brokerName, brokerData);
                }
                String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);
                registerFirst = registerFirst || (null == oldAddr);

Step3: 如果Broker為Master,并且Broker Topic配置信息發變化或者是初次注冊,則需要創建或更新Topic路由元數據,填充topicQueueTable,其實就是為默認主題自動注冊路由信息,其中包含MixAll.DEFAULT_TOPIC的路由信息。當消費生產者發送主題時,如果該主題未創建并且BrokerConfig的autoCreateTopicEnable為true時,則返回MixAll.DEFAULT_TOPIC的路由信息。

                if (null != topicConfigWrapper
                    && MixAll.MASTER_ID == brokerId) {
                    if (this.isBrokerTopicConfigChanged(brokerAddr, topicConfigWrapper.getDataVersion())
                        || registerFirst) {
                        ConcurrentMap<String, TopicConfig> tcTable =
                            topicConfigWrapper.getTopicConfigTable();
                        if (tcTable != null) {
                            for (Map.Entry<String, TopicConfig> entry : tcTable.entrySet()) {
                                this.createAndUpdateQueueData(brokerName, entry.getValue());
                            }
                        }
                    }
                }

根據TopicConfig創建QueueData數據結構,然后更新topicQueueTable
RouteInfoManager#createAndUpdateQueueData

    private void createAndUpdateQueueData(final String brokerName, final TopicConfig topicConfig) {
        QueueData queueData = new QueueData();
        queueData.setBrokerName(brokerName);
        queueData.setWriteQueueNums(topicConfig.getWriteQueueNums());
        queueData.setReadQueueNums(topicConfig.getReadQueueNums());
        queueData.setPerm(topicConfig.getPerm());
        queueData.setTopicSynFlag(topicConfig.getTopicSysFlag());

        List<QueueData> queueDataList = this.topicQueueTable.get(topicConfig.getTopicName());
        if (null == queueDataList) {
            queueDataList = new LinkedList<QueueData>();
            queueDataList.add(queueData);
            this.topicQueueTable.put(topicConfig.getTopicName(), queueDataList);
            log.info("new topic registered, {} {}", topicConfig.getTopicName(), queueData);
        } else {
            boolean addNewOne = true;

            Iterator<QueueData> it = queueDataList.iterator();
            while (it.hasNext()) {
                QueueData qd = it.next();
                if (qd.getBrokerName().equals(brokerName)) {
                    if (qd.equals(queueData)) {
                        addNewOne = false;
                    } else {
                        log.info("topic changed, {} OLD: {} NEW: {}", topicConfig.getTopicName(), qd,
                            queueData);
                        it.remove();
                    }
                }
            }

            if (addNewOne) {
                queueDataList.add(queueData);
            }
        }
    }

Step4: 更新BrokerLiveInfo,存活Broker信息表,BrokerLiveInfo是執行路由刪除的重要依據

RouteInfoManager#registerBroker

                BrokerLiveInfo prevBrokerLiveInfo = this.brokerLiveTable.put(brokerAddr,
                    new BrokerLiveInfo(
                        System.currentTimeMillis(),
                        topicConfigWrapper.getDataVersion(),
                        channel,
                        haServerAddr));
                if (null == prevBrokerLiveInfo) {
                    log.info("new broker registered, {} HAServer: {}", brokerAddr, haServerAddr);
                }

Step5: 注冊Broker的過濾器Server地址列表,一個Broker上會關聯多個FilterServer消息過濾服務器;如果此Broker為從節點,則需要查找該Broker的Master的節點信息,并更新對應的masterAddr屬性。

                if (filterServerList != null) {
                    if (filterServerList.isEmpty()) {
                        this.filterServerTable.remove(brokerAddr);
                    } else {
                        this.filterServerTable.put(brokerAddr, filterServerList);
                    }
                }

                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);
                        }
                    }
                }

路由刪除

NameServer會每隔10s掃描brokerLiveTable狀態表,如果BrokerLive的lastUpdateTimestamp的時間戳距當前時間超過120s,則認為Broker失效,移除該Broker,關閉與Broker連接,并同時更新topicQueueTable、brokerAddrTable、brokerLiveTable、filterServerTable。

RocketMQ有兩個觸發點來出發路由刪除。
1、NameServer定時掃描brokerLiveTable檢測上次心跳包與當前系統時間的時間差,如果時間戳大于120s,則需要移除該Broker信息。
2、Broker在正常被關閉的情況下,會執行unregisterBroker指令。
由于不管是何種方式出發的路由刪除,路由刪除的方法都是一樣的,就是從topicQueueTable、brokerAddrTable、brokerLiveTable、filterServerTable刪除與該Broker相關的信息。

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());
            }
        }
    }

遍歷brokerLiveInfo路由表(HashMap),檢測BrokerLiveInfo的lastUpdateTimestamp上次收到心跳包的時間如果超過當前時間120s,NameServer則認為該Broker已不可用,故需要將它移除,關閉Channel,然后刪除與該Broker相關的路由信息,路由表維護過程,需要申請寫鎖。

Step1: 申請寫鎖,根據brokerAddress從brokerLiveTable、filterServerTable移除

RouteInfoManager#onChannelDestroy

                    this.lock.writeLock().lockInterruptibly();
                    this.brokerLiveTable.remove(brokerAddrFound);
                    this.filterServerTable.remove(brokerAddrFound);

Step2: 維護brokerAddrTable。遍歷從HashMap<String/* brokerName * /, BrokerData> brokerAddrTable,從BrokerData的HashMap<Long/* brokerId * /, String/* broker address * /> brokerAddrs中,找到具體的Broker,從BrokerData中移除,如果移除后在BrokerData中不再包含其他Broker,則在brokerAddrTable中移除該brokerName對應的條目。

RouteInfoManager#onChannelDestroy

                    String brokerNameFound = null;
                    boolean removeBrokerName = false;
                    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());
                        }

Step3: 根據BrokerName,從clusterAddrTable中找到Broker并從集群中移除。如果移除后,集群中不包含任何Broker,則將該集群從clusterAddrTable中移除。

RouteInfoManager#onChannelDestroy

                    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;
                            }
                        }
                    }

Step4: 根據brokerName,遍歷所有主題的隊列,如果隊列中包含了當前Broker的隊列,則移除,如果topic只包含待移除Broker的隊列的話,從路由表中刪除該topic。

RouteInfoManager#onChannelDestroy

                    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);
                            }
                        }
                    }

Step5: 釋放鎖,完成路由刪除。

RouteInfoManager#onChannelDestroy

                finally {
                    this.lock.writeLock().unlock();
                }

路由發現

RocketMQ路由發現是非實時的,當Topic路由出現變化后,NameServer不主動推送給客戶端,而是由客戶端定時拉取主題最新的路由。根據主題名稱拉取路由信息的命令編碼為: GET_ROUTEINFO_BY_TOPIC。

private String orderTopicConf;
private List<QueueData> queueDatas;
private List<BrokerData> brokerDatas;
private HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;

• orderTopicConf: 順序消息配置內容,來自于kvConfig。
• List<QueueData> queueDatas: topic隊列元數據
• List<BrokerData> brokerDatas: topic分布的broker元數據
• HashMap<String/* brokerAddr /, List<String>/ Filter Server */> filterServerTable: broker上過濾服務器地址列表。

NameServer路由發現實現類: DefaultRequestProcessor#getRouteInfoByTopic

DefaultRequestProcessor#getRouteInfoByTopic

    public RemotingCommand getRouteInfoByTopic(ChannelHandlerContext ctx,
        RemotingCommand request) throws RemotingCommandException {
        final RemotingCommand response = RemotingCommand.createResponseCommand(null);
        final GetRouteInfoRequestHeader requestHeader =
            (GetRouteInfoRequestHeader) request.decodeCommandCustomHeader(GetRouteInfoRequestHeader.class);

        TopicRouteData topicRouteData = this.namesrvController.getRouteInfoManager().pickupTopicRouteData(requestHeader.getTopic());

        if (topicRouteData != null) {
            if (this.namesrvController.getNamesrvConfig().isOrderMessageEnable()) {
                String orderTopicConf =
                    this.namesrvController.getKvConfigManager().getKVConfig(NamesrvUtil.NAMESPACE_ORDER_TOPIC_CONFIG,
                        requestHeader.getTopic());
                topicRouteData.setOrderTopicConf(orderTopicConf);
            }

            byte[] content = topicRouteData.encode();
            response.setBody(content);
            response.setCode(ResponseCode.SUCCESS);
            response.setRemark(null);
            return response;
        }

        response.setCode(ResponseCode.TOPIC_NOT_EXIST);
        response.setRemark("No topic route info in name server for the topic: " + requestHeader.getTopic()
            + FAQUrl.suggestTodo(FAQUrl.APPLY_TOPIC_URL));
        return response;
    }

Step1: 調用RouterInfoManager的方法,從路由表topicQueueTable、brokerAddrTable、filterServerTable中分別填充TopicRouteData中的List<QueueData>、List<BrokerData>和filterServer地址表。
Step2: 如果找到主題對應的路由信息并且該主題為順序消息,則從NameServer KVconfig中獲取關于順序消息相關的配置填充路由信息。如果找不到路由信息CODE則使用TOPIC_NOT_EXISTS,表示沒有找到對應的路由。

有些內容摘錄在<<RocketMQ技術內幕>>