RocketMQ源码分析----Producer启动过程

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总体流程

首先从demo为入口分析整个启动过程

	public static void main(String[] args) throws MQClientException {DefaultMQProducer producer = new DefaultMQProducer("ProducerGroupName");producer.setNamesrvAddr("127.0.0.1:9876");producer.start();try {String message = "send message";final Message msg = new Message("topic", "tag",// tagmessage.getBytes());// bodySendResult sendResult = producer.send(msg);producer.shutdown();} catch (Exception e) {e.printStackTrace();}}

DefaultMQProducer构造方法如下：

    public DefaultMQProducer(final String producerGroup, RPCHook rpcHook) {this.producerGroup = producerGroup;defaultMQProducerImpl = new DefaultMQProducerImpl(this, rpcHook);}public DefaultMQProducer(final String producerGroup) {this(producerGroup, null);}

然后调用start方法后，即开始初始化流程，其间接调用了DefaultMQProducerImpl的start方法，即上面构造方法创建的DefaultMQProducerImpl，代码如下：

    public void start() throws MQClientException {this.start(true);}public void start(final boolean startFactory) throws MQClientException {switch (this.serviceState) {case CREATE_JUST:this.serviceState = ServiceState.START_FAILED;// 检查producerGroupthis.checkConfig();// 如果producerGroup为该值，则改变instanceName为pidif (!this.defaultMQProducer.getProducerGroup().equals(MixAll.CLIENT_INNER_PRODUCER_GROUP)) {this.defaultMQProducer.changeInstanceNameToPID();}// 获取或者创建客户端实例this.mQClientFactory = MQClientManager.getInstance().getAndCreateMQClientInstance(this.defaultMQProducer, rpcHook);// 实例注册，实际是放到一个map中，producerGroupboolean registerOK = mQClientFactory.registerProducer(this.defaultMQProducer.getProducerGroup(), this);if (!registerOK) {this.serviceState = ServiceState.CREATE_JUST;throw new MQClientException("The producer group[" + this.defaultMQProducer.getProducerGroup()+ "] has been created before, specify another name please." + FAQUrl.suggestTodo(FAQUrl.GROUP_NAME_DUPLICATE_URL),null);}this.topicPublishInfoTable.put(this.defaultMQProducer.getCreateTopicKey(), new TopicPublishInfo());if (startFactory) {// 是否要启动该实例mQClientFactory.start();}this.serviceState = ServiceState.RUNNING;break;case 其他状态不处理://....}// 心跳发送this.mQClientFactory.sendHeartbeatToAllBrokerWithLock();}

MQClientInstance创建和启动

MQClientInstance主要是客户端的一些操作的集合(不知道该怎么总结好…)，通过MQClientManager的getAndCreateMQClientInstance方法创建，这里使用了单例模式去创建MQClientManager

   public MQClientInstance getAndCreateMQClientInstance(final ClientConfig clientConfig) {return getAndCreateMQClientInstance(clientConfig, null);}public MQClientInstance getAndCreateMQClientInstance(final ClientConfig clientConfig, RPCHook rpcHook) {//ip@instanceName@unitNameString clientId = clientConfig.buildMQClientId();MQClientInstance instance = this.factoryTable.get(clientId);if (null == instance) {// 创建MQClientInstance并放入map中instance =new MQClientInstance(clientConfig.cloneClientConfig(),this.factoryIndexGenerator.getAndIncrement(), clientId, rpcHook);MQClientInstance prev = this.factoryTable.putIfAbsent(clientId, instance);if (prev != null) {instance = prev;} else {}}return instance;}

构造方法如下：

    public MQClientInstance(ClientConfig clientConfig, int instanceIndex, String clientId, RPCHook rpcHook) {this.clientConfig = clientConfig;this.instanceIndex = instanceIndex;// 通信服务的一些配置this.nettyClientConfig = new NettyClientConfig();//设置线程数this.nettyClientConfig.setClientCallbackExecutorThreads(clientConfig.getClientCallbackExecutorThreads());//网络请求的处理器this.clientRemotingProcessor = new ClientRemotingProcessor(this);// 客户端一些基础APIthis.mQClientAPIImpl = new MQClientAPIImpl(this.nettyClientConfig, this.clientRemotingProcessor, rpcHook, clientConfig);if (this.clientConfig.getNamesrvAddr() != null) {this.mQClientAPIImpl.updateNameServerAddressList(this.clientConfig.getNamesrvAddr());}this.clientId = clientId;this.mQAdminImpl = new MQAdminImpl(this);// 拉取消息服务this.pullMessageService = new PullMessageService(this);// rebalance服务this.rebalanceService = new RebalanceService(this);//创建一个group为CLIENT_INNER_PRODUCER_GROUP的producer// 该producer主要用于将消息发回Brokerthis.defaultMQProducer = new DefaultMQProducer(MixAll.CLIENT_INNER_PRODUCER_GROUP);// 将用户自建的producer属性复制过来lithis.defaultMQProducer.resetClientConfig(clientConfig);// Consumer一些消费情况(TPS,RT等)的统计管理this.consumerStatsManager = new ConsumerStatsManager(this.scheduledExecutorService);}

可以看到MQClientInstance里包含了客户端(Producer、Consumer)的一些通用操作以及一些属性的保存，其中一些具体是功能后续文章分析

上面有点需要注意：

在判断producerGroup为MixAll.CLIENT_INNER_PRODUCER_GROUP时会改变InstanceName为pid，为什么需要这样做呢？

个人理解如下：
由于该Producer是系统内置的producer，用户系统行为的消息发送，如果一个JVM内用户启动了多个Producer，那么内置的producer是可以用一个的，所以这里将instanceName改成pid就好了，那么在getAndCreateMQClientInstance中获取的clientId(ip@instanceName@unitName)就会一样，就能取出之前创建的MQClientInstance对象

启动方法如下：

    public void start() throws MQClientException {synchronized (this) {switch (this.serviceState) {case CREATE_JUST:this.serviceState = ServiceState.START_FAILED;// If not specified,looking address from name serverif (null == this.clientConfig.getNamesrvAddr()) {this.clientConfig.setNamesrvAddr(this.mQClientAPIImpl.fetchNameServerAddr());}//netty相关通信的初始化，然后开启一个定时任务扫描responseTablethis.mQClientAPIImpl.start();// 启动定时任务this.startScheduledTask();// 启动消息拉取服务this.pullMessageService.start();// 启动Rebalance拉取服务this.rebalanceService.start();// 启动内置producerthis.defaultMQProducer.getDefaultMQProducerImpl().start(false);this.serviceState = ServiceState.RUNNING;break;case//其他状态不处理;}}}