1.前言
此文章是在儒猿课程中的学习笔记，感兴趣的想看原来的课程可以去咨询儒猿课堂《从0开始带你成为RocketMQ高手》，我本人觉得这个作者还是不错，都是从场景来进行分析，感觉还是挺适合我这种小白的。这块主要都是我自己的学习笔记。想看原版的，还是去儒猿课堂。
这篇文章紧挨着上一篇文章NameServer接收Broker的注册请求处理-CSDN博客
前面我们已经看到了NameServer处理Broker的注册请求的源码流程，NameServer核心就是基于Netty服务器来接收Broker注册请求，然后交给DefaultRequestProcessor这个请求处理组件，来注册Broker注册请求。Broker的注册逻辑是放在RouteInfoManager这个路由数据管理组件实现的。最终这些路由数据都会存放到RouteInfoManager内部的一些Map数据结构组成的路由数据表中。
2.Broker 如何进行定时发送心跳
那么Broker是如何定时发送心跳到NameServer，让NameServer感知到Broker一直存活，这个Broker中的发送注册请求给NameServer，这个代码的入口还是在BrokerController中
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {@Overridepublic void run() {try {BrokerController.this.registerBrokerAll(true, false, brokerConfig.isForceRegister());} catch (Throwable e) {log.error("registerBrokerAll Exception", e);}}}, 1000 * 10, Math.max(10000, Math.min(brokerConfig.getRegisterNameServerPeriod(), 60000)), TimeUnit.MILLISECONDS);这块代码，就是启动了一个定时调度的任务，默认是每30s就会执行Broker的注册请求。
我们紧接着看下RouteInfoManager的注册方法的代码逻辑：
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 {//这里有一个加锁的操作this.lock.writeLock().lockInterruptibly();//从clusterAddrTable中获取clusterName对应的BrokeName的set集合//如果对应的clusterName中没有set集合那么就新建一个set集合Set<String> brokerNames = this.clusterAddrTable.computeIfAbsent(clusterName, k -> new HashSet<>());//直接将brokerName添加到set集合中//每次心跳过来了 都要进行添加 用set集合保证brokerName的唯一性brokerNames.add(brokerName);boolean registerFirst = false;//这里是根据BrokerName进行获取Broker的数据BrokerData brokerData = this.brokerAddrTable.get(brokerName);if (null == brokerData) {//如果为空的话 设置registerFirst为true 这个代表是第一次注册的registerFirst = true;brokerData = new BrokerData(clusterName, brokerName, new HashMap<>());this.brokerAddrTable.put(brokerName, brokerData);}//下面的这些代码应该是设置如果brokerAddrMap中没有这个brokerId对应的地址那么就添加这个地址//有的话 就要进行判断地址是否正确，不正确的就要修改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 brokerAddrTableIterator<Entry<Long, String>> it = brokerAddrsMap.entrySet().iterator();while (it.hasNext()) {Entry<Long, String> item = it.next();if (null != brokerAddr && brokerAddr.equals(item.getValue()) && brokerId != item.getKey()) {log.debug("remove entry {} from brokerData", item);it.remove();}}String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);if (MixAll.MASTER_ID == brokerId) {log.info("cluster [{}] brokerName [{}] master address change from {} to {}",brokerData.getCluster(), brokerData.getBrokerName(), oldAddr, 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()) {this.createAndUpdateQueueData(brokerName, entry.getValue());}}}}//这里就是放入Broker中心跳信息//每次心跳请求过来之后都要进行重新创建一个BrokerLiveInfo对象 对上一次心跳的信息进行覆盖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);}//下面的代码感觉跟心跳的关联关系不大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);}}}} finally {this.lock.writeLock().unlock();}} catch (Exception e) {log.error("registerBroker Exception", e);}return result;}3.NameSever如何进行故障感知
经过前面的代码我们可以看出来，每隔30s进行发送注册请求的时候，都会针对RouteInfoManager中的brokerLiveTable对上一次已经发送的注册请求进行覆盖。
我们紧接着看下NameServer是如何进行故障感知的，我们直接看NameServer中的initialize方法，可以直接找到这个代码：
his.scheduledExecutorService.scheduleAtFixedRate(NamesrvController.this.routeInfoManager::scanNotActiveBroker, 5, 10, TimeUnit.SECONDS);
这行代码的主要作用就，就是启动一个定时调度线程，每隔10s进行扫描一次RouteInfoManager的scanNotActiveBroker方法，我们接下来看下这个方法，
public int scanNotActiveBroker() {// 这块的方法主要是brokerLiveTable的集合中的所有元素//拿到broker最新一次的心跳时间 //broker的最新一次心跳时间+120s 小于 当前时间戳 //就把这个broker进行移除掉int removeCount = 0;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());removeCount++;}}return removeCount;}4.总结
我们还是用一张图来进行总结这篇博客的内容：
