在创建完成Producer后，就进入了Producer的start()方法。start()方法DefaultMQProducerImpl的start()方法。
this.serviceState = ServiceState.START_FAILED;
this.checkConfig();
if (!this.defaultMQProducer.getProducerGroup().equals(MixAll.CLIENT_INNER_PRODUCER_GROUP)) {
this.defaultMQProducer.changeInstanceNameToPID();
}
this.mQClientFactory = MQClientManager.getInstance().getAndCreateMQClientInstance(this.defaultMQProducer, rpcHook);
boolean 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) {
mQClientFactory.start();
}
log.info("the producer [{}] start OK. sendMessageWithVIPChannel={}", this.defaultMQProducer.getProducerGroup(),
this.defaultMQProducer.isSendMessageWithVIPChannel());
this.serviceState = ServiceState.RUNNING;
上面现将状态设置为START_FAILED，启动成功后再设置为RUNNING状态。
this.checkConfig(); 检查是否设置group
前面的代码都是做下缓存，没有功能的实际意义，真正的启动是在
mQClientFactory.start();
this.serviceState = ServiceState.START_FAILED;
// If not specified,looking address from name server
if (null == this.clientConfig.getNamesrvAddr()) {
this.mQClientAPIImpl.fetchNameServerAddr();
}
// Start request-response channel
this.mQClientAPIImpl.start();
// Start various schedule tasks
this.startScheduledTask();
// Start pull service
this.pullMessageService.start();
// Start rebalance service
this.rebalanceService.start();
// Start push service
this.defaultMQProducer.getDefaultMQProducerImpl().start(false);
log.info("the client factory [{}] start OK", this.clientId);
this.serviceState = ServiceState.RUNNING;
1、获取NameServer
if (null == this.clientConfig.getNamesrvAddr()) {
this.mQClientAPIImpl.fetchNameServerAddr();
}
上面这段是获取NameServer
2、启动channel
众所周知，RocketMQ通讯是通过Netty的，Netty的通信需要通过channel
this.mQClientAPIImpl.start();
就是初始化channel。
这个start()方法，进入了NettyRemotingClient的start()方法，这这个start方法的前面一部分是在创建netty通讯的客户端
Bootstrap handler = this.bootstrap.group(this.eventLoopGroupWorker).channel(NioSocketChannel.class)
this.timer.scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
try {
NettyRemotingClient.this.scanResponseTable();
} catch (Throwable e) {
log.error("scanResponseTable exception", e);
}
}
}, 1000 * 3, 1000);
是检查发送的消息是否超时，并做相应处理。
this.timer.scheduleAtFixedRate(new TimerTask() {
@Override
public void run() {
try {
NettyRemotingClient.this.scanChannelTablesOfNameServer();
} catch (Exception e) {
log.error("scanChannelTablesOfNameServer exception", e);
}
}
}, 1000 * 3, 10 * 1000);
上面这段代码是通过心跳检查查看NameServer的连接是佛正常。
3、启动多个定时任务
this.startScheduledTask();
其中的方法拆开分析如下：
if (null == this.clientConfig.getNamesrvAddr()) {
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.mQClientAPIImpl.fetchNameServerAddr();
} catch (Exception e) {
log.error("ScheduledTask fetchNameServerAddr exception", e);
}
}
}, 1000 * 10, 1000 * 60 * 2, TimeUnit.MILLISECONDS);
}
每个2分钟更新一个NameServer。
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.updateTopicRouteInfoFromNameServer();
} catch (Exception e) {
log.error("ScheduledTask updateTopicRouteInfoFromNameServer exception", e);
}
}
}, 10, this.clientConfig.getPollNameServerInterval(), TimeUnit.MILLISECONDS);
更新topic在NameServer中的路由信息。
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.cleanOfflineBroker();
MQClientInstance.this.sendHeartbeatToAllBrokerWithLock();
} catch (Exception e) {
log.error("ScheduledTask sendHeartbeatToAllBroker exception", e);
}
}
}, 1000, this.clientConfig.getHeartbeatBrokerInterval(), TimeUnit.MILLISECONDS);
上面这段是清除下线的Broker，并与Broker的心跳检测，后面发送消息，真正的通讯是与Broker直接进行的。
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.persistAllConsumerOffset();
} catch (Exception e) {
log.error("ScheduledTask persistAllConsumerOffset exception", e);
}
}
}, 1000 * 10, this.clientConfig.getPersistConsumerOffsetInterval(), TimeUnit.MILLISECONDS);
上面是将消费端的offset持久化到你本机上。
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
try {
MQClientInstance.this.adjustThreadPool();
} catch (Exception e) {
log.error("ScheduledTask adjustThreadPool exception", e);
}
}
}, 1, 1, TimeUnit.MINUTES);
上面这段是调整发送消息的线程池的大小，其实是空方法，不起作用。
4、启动拉取消息的线程
this.pullMessageService.start();
上面这个方法是启动拉取消息的线程。
5、启动重新负载均衡的线程
this.rebalanceService.start();
上面的方法，会根据topic或者服务的变化等重新进行负载均衡。
this.defaultMQProducer.getDefaultMQProducerImpl().start(false);
上面这段，把之前的方法再验证一遍，没有实际意义。
至此，producer的start()方法就结束了。
二、super.start()
在ProducerImpl的super.start()方法中，就是做了一件事，不停将消息的轨迹持久化到控制台。
public void start() throws MQClientException {
TraceProducerFactory.registerTraceDispatcher(dispatcherId);
this.worker = new Thread(new AsyncRunnable(), "MQ-AsyncArrayDispatcher-Thread-" + dispatcherId);
this.worker.setDaemon(true);
this.worker.start();
this.registerShutDownHook();
}
