nameServer

nameServer是一個服務中心, 用於broker的註冊, 然後consumer和producer通過連線namesrv獲取broker的資訊, namesrv是無狀態的節點, 這意味著它不會有主從之分

以下是官方文件對namesrv的概念說明

名稱服務充當路由訊息的提供者。生產者或消費者能夠通過名字服務查詢各主題相應的Broker IP列表。多個Namesrv例項組成叢集，但相互獨立，沒有資訊交換。

namesrv的啟動需要設定啟動引數

-c /home/rocketmq/conf/namesrv.properties 設定配置檔案

在配置檔案中可以設定rocketmqHome, 它的作用會在後面namesrv原始碼中有所體現

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

    public static NamesrvController main0(String[] args) {

        try {
            // 建立namesrv的控制器
            NamesrvController controller = createNamesrvController(args);
            // 啟動控制器, 啟動namesrv服務
            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;
    }

main方法很簡單, 他僅僅建立了一個nameSrv的控制器, 然後啟動控制器而已

這裡只給出重要的部分

public static NamesrvController createNamesrvController(String[] args) throws IOException, JoranException {
        // 構建命令列選項nameServer地址和help
        Options options = ServerUtil.buildCommandlineOptions(new Options());
        // 如果options中是help則列印help資訊然後退出
        // 給options中新增c:{配置檔案}和p:{列印配置資訊}引數
        commandLine = ServerUtil.parseCmdLine("mqnamesrv", args, buildCommandlineOptions(options), new PosixParser());
        if (null == commandLine) {
            System.exit(-1);
            return null;
        }

        final NamesrvConfig namesrvConfig = new NamesrvConfig();
        final NettyServerConfig nettyServerConfig = new NettyServerConfig();
    	// 設定了namesrv的埠資訊
        nettyServerConfig.setListenPort(9876);
        if (commandLine.hasOption('c')) {
            // 獲取配置檔案地址
            String file = commandLine.getOptionValue('c');
            if (file != null) {
                // 建立輸入流讀取配置檔案
                InputStream in = new BufferedInputStream(new FileInputStream(file));
                properties = new Properties();
                properties.load(in);
                // 通過反射設定物件引數
                MixAll.properties2Object(properties, namesrvConfig);
                MixAll.properties2Object(properties, nettyServerConfig);

                namesrvConfig.setConfigStorePath(file);

                System.out.printf("load config properties file OK, %s%n", file);
                in.close();
            }
        }
        MixAll.properties2Object(ServerUtil.commandLine2Properties(commandLine), namesrvConfig);
        // rocketmqHome的值是從args中獲取的, 啟動時需要配置
        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);
        }

        final NamesrvController controller = new NamesrvController(namesrvConfig, nettyServerConfig);

        // remember all configs to prevent discard
        controller.getConfiguration().registerConfig(properties);

        return controller;
    }

controller的建立就是

1. 設定rocketmq的版本
2. 設定namesrv埠
3. 讀取預設的配置檔案

接下去就是controller的啟動

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

        if (null == controller) {
            throw new IllegalArgumentException("NamesrvController is null");
        }
		// 做controller的初始化
        boolean initResult = controller.initialize();
        if (!initResult) {
            controller.shutdown();
            System.exit(-3);
        }
        // 新增結束的鉤子函式
        Runtime.getRuntime().addShutdownHook(new ShutdownHookThread(log, new Callable<Void>() {
            @Override
            public Void call() throws Exception {
                controller.shutdown();
                return null;
            }
        }));
		//啟動
        controller.start();

        return controller;
    }

在controller的初始化中做了以下幾件事情

1. 將namesrv的配置檔案中設定的kvConfig讀取出來
2. 開始初始化netty, 根據作業系統(linux是epoll)設定了bossLoop和selector
3. 根據配置中設定的執行緒數量設定並初始化了netty使用到的執行緒池
4. 註冊了處理器(處理器用於netty的業務邏輯處理), 由於rocketmq的所有模組使用的netty程式都是相同的一段, 所以這裡使用到了享元模式將netty中處理業務邏輯的部分抽離出來
5. 啟動一個服務, 每十秒掃描一次停止活動的broker, 並且移除
6. 啟動一個服務, 每十秒列印一次所有配置

以下是部分原始碼

public boolean initialize() {

        this.kvConfigManager.load();

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

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

        // 註冊處理器, 這裡註冊了存放了註冊broker的處理器
        this.registerProcessor();

        // 掃描停止活動的broker 10秒執行一次
        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;
    }

在controller的啟動流程中, 僅僅是做了兩件事情

1. 啟動netty服務
2. 如果檔案監聽服務存在則啟動

namesrv提供的是服務, 所以只需要啟動netty的服務端

        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, handshakeHandler)
                            .addLast(defaultEventExecutorGroup,
                                encoder,
                                new NettyDecoder(),
                                new IdleStateHandler(0, 0, nettyServerConfig.getServerChannelMaxIdleTimeSeconds()),
                                connectionManageHandler,
                                serverHandler
                            );
                    }
                });

可以看見這裡設定了serverHandler這個處理器來處理事件

而serverHandler中的channelRead0方法呼叫了抽象類NettyRemotingAbstract的processMessageReceived方法

public void processMessageReceived(ChannelHandlerContext ctx, RemotingCommand msg) throws Exception {
        final RemotingCommand cmd = msg;
        if (cmd != null) {
            switch (cmd.getType()) {
                case REQUEST_COMMAND:
                    processRequestCommand(ctx, cmd);
                    break;
                case RESPONSE_COMMAND:
                    processResponseCommand(ctx, cmd);
                    break;
                default:
                    break;
            }
        }
    }

由於該方法被client和server都會呼叫, 所以需要判斷訊息是請求還是響應型別, 顯然傳送給server的訊息都是請求型別

processRequestCommand該方法會判斷訊息中的code來判斷使用何種處理器, 這裡的處理器就是在初始化的時候註冊的

public void processRequestCommand(final ChannelHandlerContext ctx, final RemotingCommand cmd) {
        // 根據RequestCode獲取具體的處理器
        final Pair<NettyRequestProcessor, ExecutorService> matched = this.processorTable.get(cmd.getCode());
        // 沒有獲取到處理器就用預先設定的預設處理器
        final Pair<NettyRequestProcessor, ExecutorService> pair = null == matched ? this.defaultRequestProcessor : matched;
        final int opaque = cmd.getOpaque();

        if (pair != null) {
            Runnable run = new Runnable() {
                @Override
                public void run() {
                    try {
                        doBeforeRpcHooks(RemotingHelper.parseChannelRemoteAddr(ctx.channel()), cmd);
                        final RemotingResponseCallback callback = new RemotingResponseCallback() {
                            @Override
                            public void callback(RemotingCommand response) {
                                doAfterRpcHooks(RemotingHelper.parseChannelRemoteAddr(ctx.channel()), cmd, response);
                                if (!cmd.isOnewayRPC()) {
                                    if (response != null) {
                                        response.setOpaque(opaque);
                                        response.markResponseType();
                                        try {
                                            ctx.writeAndFlush(response);
                                        } catch (Throwable e) {
                                            log.error("process request over, but response failed", e);
                                            log.error(cmd.toString());
                                            log.error(response.toString());
                                        }
                                    } else {
                                    }
                                }
                            }
                        };
                        // 根據不同的處理器使用不同方法, 非同步請求則非同步處理
                        if (pair.getObject1() instanceof AsyncNettyRequestProcessor) {
                            AsyncNettyRequestProcessor processor = (AsyncNettyRequestProcessor)pair.getObject1();
                            processor.asyncProcessRequest(ctx, cmd, callback);
                        } else {
                            NettyRequestProcessor processor = pair.getObject1();
                            RemotingCommand response = processor.processRequest(ctx, cmd);
                            callback.callback(response);
                        }
                    } catch (Throwable e) {
                        log.error("process request exception", e);
                        log.error(cmd.toString());

                        if (!cmd.isOnewayRPC()) {
                            final RemotingCommand response = RemotingCommand.createResponseCommand(RemotingSysResponseCode.SYSTEM_ERROR,
                                RemotingHelper.exceptionSimpleDesc(e));
                            response.setOpaque(opaque);
                            ctx.writeAndFlush(response);
                        }
                    }
                }
            };
    }

broker的註冊

預設請求處理器中的switch存在如下程式碼

case RequestCode.REGISTER_BROKER: // 註冊broker
                Version brokerVersion = MQVersion.value2Version(request.getVersion());
                if (brokerVersion.ordinal() >= MQVersion.Version.V3_0_11.ordinal()) {
                    return this.registerBrokerWithFilterServer(ctx, request);
                } else {
                    return this.registerBroker(ctx, request);
                }

broker註冊的時候, code會被設定為REGISTER_BROKER

namesrv識別到這一code就會進入註冊方法, 在3.0.11版本後加入了請求過濾

RocketMQ的消費者可以根據Tag進行訊息過濾，也支援自定義屬性過濾。訊息過濾目前是在Broker端實現的，優點是減少了對於Consumer無用訊息的網路傳輸，缺點是增加了Broker的負擔、而且實現相對複雜。

訊息過濾的實現本文暫時不細究

在registerBrokerWithFilterServer方法中設定了響應頭, 呼叫了broker的註冊方法

響應頭資訊尤為重要, 該響應頭中帶有高可用服務地址和master的地址, 該資訊對於broker的高可用服務的通訊有影響

下面看看registerBroker方法是如何註冊的

    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 {
                this.lock.writeLock().lockInterruptibly();
                // 獲取該broker叢集下面的所有broker名稱
                Set<String> brokerNames = this.clusterAddrTable.get(clusterName);
                if (null == brokerNames) {
                    brokerNames = new HashSet<String>();
                    this.clusterAddrTable.put(clusterName, brokerNames);
                }
                // 新增當前註冊的broker
                brokerNames.add(brokerName);

                boolean registerFirst = false;

                // 此前如果有註冊過就直接獲取, 沒註冊過就註冊
                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);
                }
                Map<Long, String> brokerAddrsMap = brokerData.getBrokerAddrs();
                //Switch slave to master: first remove <1, IP:PORT> in namesrv, then add <0, IP:PORT>
                //The same IP:PORT must only have one record in brokerAddrTable
                // 主從broker的brokername是一樣的
                // 這裡用於從服務升級為主服務
                Iterator<Entry<Long, String>> it = brokerAddrsMap.entrySet().iterator();
                while (it.hasNext()) {
                    Entry<Long, String> item = it.next();
                    // 如果原先該地址已經註冊過, 並且brokerId與此前不同則從map中移除該元素
                    if (null != brokerAddr && brokerAddr.equals(item.getValue()) && brokerId != item.getKey()) {
                        it.remove();
                    }
                }
                
                String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);
                registerFirst = registerFirst || (null == oldAddr);

                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()) {
                                // topicQueueTable中存入broker資訊
                                this.createAndUpdateQueueData(brokerName, entry.getValue());
                            }
                        }
                    }
                }
			   // 設定broker的實時資訊
                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);
                }

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

                // 如果是slave註冊, 則會設定一個master地址
                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 {
                this.lock.writeLock().unlock();
            }
        } catch (Exception e) {
            log.error("registerBroker Exception", e);
        }

        return result;
    }

註冊broker的時候在namesrv中用0, 1 來標識了broker的主從, 並且會給從服務設定主服務的地址

consumer根據topic獲取broker資訊

consumer獲取broker資訊的時候code會設定為GET_ROUTEINFO_BY_TOPIC

然後去namesrv獲取該topic下的broker資訊

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

        // 這裡根據topic從topicQueueTable獲取brokerName
        // 而後根據brokerName從brokerAddrTable獲取broker資訊
        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;
    }

獲取broker資訊的過程很簡單, 僅僅就是根據topic去獲取之前註冊broker的時候存入的資訊就行了

後記

個人感覺namesrv是整個rocketmq中最簡單的模組, 畢竟之前是使用zookeeper做註冊中心的, namesrv主要的功能就是接受broker的註冊, 然後處理consumer和producer的獲取broker資訊請求