6RocketMQ 源码解析之 Broker 启动(上)

Posted 2022-04-15 carl-zhao

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上面一篇我们介绍了 RocketMQ 的元数据管理，它是通过自定义一个 KV 服务器。并且其它服务在 NameServer 注册服务信息的时候都是全量注册。如果 RocketMQ 的拓扑图当中有多台 NameServer 的时候，只要有一台存活的话 RocketMQ 集群就可以正常工作。

当 RocketMQ 作为消息队列要向外提供服务的时候，除了需要第一步启动 NameServer 用来保存元数据，还需要启动 RocketMQ 的 Broker。这样才能 Producer 才能发现消息到 Broker，然后 Consumer 才能从 Broker 消费消息。

RocketMQ 的 Broker 启动类为：org.apache.rocketmq.broker.BrokerStartup。下面我们来看一下 Broker 启动做了哪些事情。

1、解析启动命令

其实 BrokerStartup 只是一个启动类，Broker 的启动它其实是委托给 BrokerController 这个类来完成的。它的功能其实是非常强大的，要使用这个类来启动 MQ 的整个服务。Rocket 首先要对这个对象进行初始化，做为一个强大的中间件可配置化也是必须的。所以在初始化 BrokerController ，RocketMQ 会先解析我们的启动命令。还记得我们看源码的时候启动 RocketMQ 的启动命令么，如下所示：

-c /Users/carl/projects/idea/github/apache/rocketmq/config/conf/broker.conf -n localhost:9876

我们来看一下 RocketMQ 的 Broker 启动支持哪些命令：

Borker 启动命令列表

短命令	长命令	描述	解释
p	printConfigItem	Print all config item	打印所有配置项
c	configFile	Broker config properties file	Broker 的配置文件地址
h	help	Print help	打印帮助命令
m	printImportantConfig	Print important config item	打印所有重要的配置项(BrokerConfig类上面所有标注 @ImportantField 注解的属性)
n	namesrvAddr	Name server address list, eg: 192.168.0.1:9876;192.168.0.2:9876	命名服务地址列表

其实最重要的还是 Broker 的配置文件地址的解析，它会把配置文件解析成 Properties 对象，也就是 KV 键值对。然后把这些配置项赋值到以下的 Broker 配置对象当中。

BrokerConfig：Broker 服务相关的配置项
NettyServerConfig：Broker 对外暴露 Socket 服务相关的配置项(使用 Netty)
NettyClientConfig：Broker 对外调用 Socket 服务相关的配置项(使用 Netty)
MessageStoreConfig：Broker 消息存储相关的配置项

2、初始化 BrokerController

通过上面解析配置文件并把配置项添加到上面4个配置对象当中，然后调用 BrokerController 的构建函数创建它。

BrokerStartup.java

// 创建 BrokerController 对象
final BrokerController controller = new BrokerController(
    brokerConfig,
    nettyServerConfig,
    nettyClientConfig,
    messageStoreConfig);

下面我们来看一下在创建 BrokerController 做了哪些事。

    public BrokerController(
        final BrokerConfig brokerConfig,
        final NettyServerConfig nettyServerConfig,
        final NettyClientConfig nettyClientConfig,
        final MessageStoreConfig messageStoreConfig
    ) 
        this.brokerConfig = brokerConfig;
        this.nettyServerConfig = nettyServerConfig;
        this.nettyClientConfig = nettyClientConfig;
        this.messageStoreConfig = messageStoreConfig;
        // 消费者 offset 管理器
        this.consumerOffsetManager = new ConsumerOffsetManager(this);
        // Broker 的 Topic 管理器
        this.topicConfigManager = new TopicConfigManager(this);
        // 处理 Consumer 消息拉取处理器
        this.pullMessageProcessor = new PullMessageProcessor(this);
        // Consumer 消息拉取长轮训机制
        this.pullRequestHoldService = new PullRequestHoldService(this);
        // 监听收到 Producer 消息(通知 PullRequestHoldService)
        this.messageArrivingListener = new NotifyMessageArrivingListener(this.pullRequestHoldService);
        this.consumerIdsChangeListener = new DefaultConsumerIdsChangeListener(this);
        // 消费者管理器(消费者&消费者组信息)
        this.consumerManager = new ConsumerManager(this.consumerIdsChangeListener);
        // 消费者消费过滤器
        this.consumerFilterManager = new ConsumerFilterManager(this);
        // 生产者管理器(过期生产者剔除等功能)
        this.producerManager = new ProducerManager();
        // 心跳检测管理器(Producer/Consumer/FilterServer)
        this.clientHousekeepingService = new ClientHousekeepingService(this);
        // broker 与客户端通信类
        this.broker2Client = new Broker2Client(this);
        // consumer 配置管理器
        this.subscriptionGroupManager = new SubscriptionGroupManager(this);
        // broker 与外部通信 API(与 NameServer)
        this.brokerOuterAPI = new BrokerOuterAPI(nettyClientConfig);
        // Consumer 消息过滤器管理器
        this.filterServerManager = new FilterServerManager(this);
		// 消息主-从同步处理器
        this.slaveSynchronize = new SlaveSynchronize(this);

        this.sendThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getSendThreadPoolQueueCapacity());
        this.pullThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getPullThreadPoolQueueCapacity());
        this.replyThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getReplyThreadPoolQueueCapacity());
        this.queryThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getQueryThreadPoolQueueCapacity());
        this.clientManagerThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getClientManagerThreadPoolQueueCapacity());
        this.consumerManagerThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getConsumerManagerThreadPoolQueueCapacity());
        this.heartbeatThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getHeartbeatThreadPoolQueueCapacity());
        this.endTransactionThreadPoolQueue = new LinkedBlockingQueue<Runnable>(this.brokerConfig.getEndTransactionPoolQueueCapacity());

        this.brokerStatsManager = new BrokerStatsManager(this.brokerConfig.getBrokerClusterName());
        this.setStoreHost(new InetSocketAddress(this.getBrokerConfig().getBrokerIP1(), this.getNettyServerConfig().getListenPort()));

        this.brokerFastFailure = new BrokerFastFailure(this);
        this.configuration = new Configuration(
            log,
            BrokerPathConfigHelper.getBrokerConfigPath(),
            this.brokerConfig, this.nettyServerConfig, this.nettyClientConfig, this.messageStoreConfig
        );

上面 Borker 的主要功能类已经注释了。关于上面的功能可以结合 RocketMQ 的 github 地址的特性结合起来理解。在构建了 BrokerController 对象之后，会调用 BrokerController#initialize 方法对它进行初始化。

BrokerController#initialize

    public boolean initialize() throws CloneNotSupportedException 
        boolean result = this.topicConfigManager.load();

        result = result && this.consumerOffsetManager.load();
        result = result && this.subscriptionGroupManager.load();
        result = result && this.consumerFilterManager.load();

        if (result) 
            try 
                this.messageStore =
                    new DefaultMessageStore(this.messageStoreConfig, this.brokerStatsManager, this.messageArrivingListener,
                        this.brokerConfig);
                if (messageStoreConfig.isEnableDLegerCommitLog()) 
                    DLedgerRoleChangeHandler roleChangeHandler = new DLedgerRoleChangeHandler(this, (DefaultMessageStore) messageStore);
                    ((DLedgerCommitLog)((DefaultMessageStore) messageStore).getCommitLog()).getdLedgerServer().getdLedgerLeaderElector().addRoleChangeHandler(roleChangeHandler);
                
                this.brokerStats = new BrokerStats((DefaultMessageStore) this.messageStore);
                //load plugin
                MessageStorePluginContext context = new MessageStorePluginContext(messageStoreConfig, brokerStatsManager, messageArrivingListener, brokerConfig);
                this.messageStore = MessageStoreFactory.build(context, this.messageStore);
                this.messageStore.getDispatcherList().addFirst(new CommitLogDispatcherCalcBitMap(this.brokerConfig, this.consumerFilterManager));
             catch (IOException e) 
                result = false;
                log.error("Failed to initialize", e);
            
        

        result = result && this.messageStore.load();

        if (result) 
            this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.clientHousekeepingService);
            NettyServerConfig fastConfig = (NettyServerConfig) this.nettyServerConfig.clone();
            fastConfig.setListenPort(nettyServerConfig.getListenPort() - 2);
            this.fastRemotingServer = new NettyRemotingServer(fastConfig, this.clientHousekeepingService);
            this.sendMessageExecutor = new BrokerFixedThreadPoolExecutor(
                this.brokerConfig.getSendMessageThreadPoolNums(),
                this.brokerConfig.getSendMessageThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.sendThreadPoolQueue,
                new ThreadFactoryImpl("SendMessageThread_"));

            this.pullMessageExecutor = new BrokerFixedThreadPoolExecutor(
                this.brokerConfig.getPullMessageThreadPoolNums(),
                this.brokerConfig.getPullMessageThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.pullThreadPoolQueue,
                new ThreadFactoryImpl("PullMessageThread_"));

            this.replyMessageExecutor = new BrokerFixedThreadPoolExecutor(
                this.brokerConfig.getProcessReplyMessageThreadPoolNums(),
                this.brokerConfig.getProcessReplyMessageThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.replyThreadPoolQueue,
                new ThreadFactoryImpl("ProcessReplyMessageThread_"));

            this.queryMessageExecutor = new BrokerFixedThreadPoolExecutor(
                this.brokerConfig.getQueryMessageThreadPoolNums(),
                this.brokerConfig.getQueryMessageThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.queryThreadPoolQueue,
                new ThreadFactoryImpl("QueryMessageThread_"));

            this.adminBrokerExecutor =
                Executors.newFixedThreadPool(this.brokerConfig.getAdminBrokerThreadPoolNums(), new ThreadFactoryImpl(
                    "AdminBrokerThread_"));

            this.clientManageExecutor = new ThreadPoolExecutor(
                this.brokerConfig.getClientManageThreadPoolNums(),
                this.brokerConfig.getClientManageThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.clientManagerThreadPoolQueue,
                new ThreadFactoryImpl("ClientManageThread_"));

            this.heartbeatExecutor = new BrokerFixedThreadPoolExecutor(
                this.brokerConfig.getHeartbeatThreadPoolNums(),
                this.brokerConfig.getHeartbeatThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.heartbeatThreadPoolQueue,
                new ThreadFactoryImpl("HeartbeatThread_", true));

            this.endTransactionExecutor = new BrokerFixedThreadPoolExecutor(
                this.brokerConfig.getEndTransactionThreadPoolNums(),
                this.brokerConfig.getEndTransactionThreadPoolNums(),
                1000 * 60,
                TimeUnit.MILLISECONDS,
                this.endTransactionThreadPoolQueue,
                new ThreadFactoryImpl("EndTransactionThread_"));

            this.consumerManageExecutor =
                Executors.newFixedThreadPool(this.brokerConfig.getConsumerManageThreadPoolNums(), new ThreadFactoryImpl(
                    "ConsumerManageThread_"));

            this.registerProcessor();

            final long initialDelay = UtilAll.computeNextMorningTimeMillis() - System.currentTimeMillis();
            final long period = 1000 * 60 * 60 * 24;
            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() 
                @Override
                public void run() 
                    try 
                        BrokerController.this.getBrokerStats().record();
                     catch (Throwable e) 
                        log.error("schedule record error.", e);
                    
                
            , initialDelay, period, TimeUnit.MILLISECONDS);

            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() 
                @Override
                public void run() 
                    try 
                        BrokerController.this.consumerOffsetManager.persist();
                     catch (Throwable e) 
                        log.error("schedule persist consumerOffset error.", e);
                    
                
            , 1000 * 10, this.brokerConfig.getFlushConsumerOffsetInterval(), TimeUnit.MILLISECONDS);

            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() 
                @Override
                public void run() 
                    try 
                        BrokerController.this.consumerFilterManager.persist();
                     catch (Throwable e) 
                        log.error("schedule persist consumer filter error.", e);
                    
                
            , 1000 * 10, 1000 * 10, TimeUnit.MILLISECONDS);

            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() 
                @Override
                public void run() 
                    try 
                        BrokerController.this.protectBroker();
                     catch (Throwable e) 
                        log.error("protectBroker error.", e);
                    
                
            , 3, 3, TimeUnit.MINUTES);

            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() 
                @Override
                public void run() 
                    try 
                        BrokerController.this.printWaterMark();
                     catch (Throwable e) 
                        log.error("printWaterMark error.", e);
                    
                
            , 10, 1, TimeUnit.SECONDS);

            this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() 

                @Override
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