五张图告诉你 RocketMQ 为什么不使用 Zookeeper 做注册中心

//BrokerOuterAPI.java
public List<RegisterBrokerResult> registerBrokerAll(
 //省略参数
 final boolean compressed) {

 final List<RegisterBrokerResult> registerBrokerResultList = new CopyOnWriteArrayList<>();
 List<String> nameServerAddressList = this.remotingClient.getNameServerAddressList();
 if (nameServerAddressList != null && nameServerAddressList.size() > 0) {
        //省略 requestHeader 封装
  final CountDownLatch countDownLatch = new CountDownLatch(nameServerAddressList.size());
  for (final String namesrvAddr : nameServerAddressList) {
   brokerOuterExecutor.execute(new Runnable() {
    @Override
    public void run() {
     try {
      RegisterBrokerResult result = registerBroker(namesrvAddr, oneway, timeoutMills, requestHeader, body);
      if (result != null) {
       registerBrokerResultList.add(result);
      }
     } catch (Exception e) {
     } finally {
      countDownLatch.countDown();
     }
    }
   });
  }

  try {
   countDownLatch.await(timeoutMills, TimeUnit.MILLISECONDS);
  } catch (InterruptedException e) {
  }
 }
 return registerBrokerResultList;
}

//BrokerController 类
public synchronized void registerIncrementBrokerData(TopicConfig topicConfig, DataVersion dataVersion) {
 TopicConfig registerTopicConfig = topicConfig;
 //省略
 ConcurrentMap<String, TopicConfig> topicConfigTable = new ConcurrentHashMap<String, TopicConfig>();
 topicConfigTable.put(topicConfig.getTopicName(), registerTopicConfig);
 TopicConfigSerializeWrapper topicConfigSerializeWrapper = new TopicConfigSerializeWrapper();
 topicConfigSerializeWrapper.setDataVersion(dataVersion);
 topicConfigSerializeWrapper.setTopicConfigTable(topicConfigTable);

 doRegisterBrokerAll(true, false, topicConfigSerializeWrapper);
}

public boolean updateTopicRouteInfoFromNameServer(final String topic, boolean isDefault,
 DefaultMQProducer defaultMQProducer) {
 try {
  if (this.lockNamesrv.tryLock(LOCK_TIMEOUT_MILLIS, TimeUnit.MILLISECONDS)) {
   try {
    TopicRouteData topicRouteData;
    if (isDefault && defaultMQProducer != null) {
     //根据默认 Topic 来取
     topicRouteData = this.mQClientAPIImpl.getDefaultTopicRouteInfoFromNameServer(defaultMQProducer.getCreateTopicKey(),
      clientConfig.getMqClientApiTimeout());
     //省略部分逻辑
    } else {
     topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, clientConfig.getMqClientApiTimeout());
    }
    if (topicRouteData != null) {
        //判断路由信息是否发送变化
     TopicRouteData old = this.topicRouteTable.get(topic);
     boolean changed = topicRouteDataIsChange(old, topicRouteData);
     if (!changed) {
      changed = this.isNeedUpdateTopicRouteInfo(topic);
     } else {}

     if (changed) {
      TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData();

      for (BrokerData bd : topicRouteData.getBrokerDatas()) {
       this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs());
      }

      // Update Pub info
      if (!producerTable.isEmpty()) {
       //更新生产者缓存
      }

      // Update sub info
      if (!consumerTable.isEmpty()) {
       //更新消费者缓存
      }
      log.info("topicRouteTable.put. Topic = {}, TopicRouteData[{}]", topic, cloneTopicRouteData);
      this.topicRouteTable.put(topic, cloneTopicRouteData);
      return true;
     }
    } else {
     log.warn("updateTopicRouteInfoFromNameServer, getTopicRouteInfoFromNameServer return null, Topic: {}. [{}]", topic, this.clientId);
    }
   } catch (MQClientException e) {
   } catch (RemotingException e) {
   } finally {
    this.lockNamesrv.unlock();
   }
  } else {}
 } catch (InterruptedException e) {
 }
 return false;
}

public RegisterBrokerResult registerBroker(
  //省略参数
  final Channel channel) {
 RegisterBrokerResult result = new RegisterBrokerResult();
 try {
  try {
   this.lock.writeLock().lockInterruptibly();

   Set<String> brokerNames = this.clusterAddrTable.get(clusterName);
   if (null == brokerNames) {
    brokerNames = new HashSet<String>();
    this.clusterAddrTable.put(clusterName, brokerNames);
   }

   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);
   }

   BrokerLiveInfo prevBrokerLiveInfo = this.brokerLiveTable.put(brokerAddr,
     new BrokerLiveInfo(
       System.currentTimeMillis(),
       topicConfigWrapper.getDataVersion(),
       channel,
       haServerAddr));
  } finally {
   this.lock.writeLock().unlock();
  }
 } catch (Exception e) {
 }

 return result;
}