NameServer 与zk

1.nameServer 之间互不通信，故不存在强一致性，即不同的producer看到的视图可能时不一样的，（如何保证最终一致的？）

2.nameServer维护的boker信息 发生变化时，不会像zk某个节点被监听那样，给订阅放发送服务下线事件，所以订阅方无法及时发现服务下线（如何发现的？）

路由元信息

1.topicQueueTable：topic消息队列路由信息，消息发送时根据路由表进行负载均衡

2.brokerAddrTable：Broker基础信息，包含brokerName，所属集群名称，主备broker地址

3.clusterAddrTable:Broker集群信息，存储集群中所有broker名称

4.brokerLiveTable：Broker状态信息。nameserver每次收到心跳包时会替换该信息

5.filterServerTable：Broker上的FilterServer列表，用于类模式消息过滤。

一个Topic拥有多个消息队列，一个Broker为每一主题默认创建4个都队列和4个写队列，多个Broker组成一个集群，BrokerName由相同的多台Broker组成Master-Slave架构(对比kafaka：分区)，brokerId为0代表Master，大于0表示Slave。

路由注册

RocketMQ路由注册是通过Broker与NameServer的心跳功能实现的。Broker启动时向集群中所有的Name Server发送心跳语句，每隔30s向集群中所有NameServer发送心跳包，NameServer收到Broker心跳包时会更新broker，LiveTable缓存中BrokerLiveInfo的lastUpdateTimestamp，然后NameSer每隔10s扫描broker Live Tale，如果连续120s没有收到心跳包，NameServer将移除该Broker的路由信息同时关闭Socket连接

注册源码：

 public List<RegisterBrokerResult> registerBrokerAll(
        final String clusterName,
        final String brokerAddr,
        final String brokerName,
        final long brokerId,
        final String haServerAddr,
        final TopicConfigSerializeWrapper topicConfigWrapper,
        final List<String> filterServerList,
        final boolean oneway,
        final int timeoutMills,
        final boolean compressed) {

        final List<RegisterBrokerResult> registerBrokerResultList = Lists.newArrayList();
        List<String> nameServerAddressList = this.remotingClient.getNameServerAddressList();
        if (nameServerAddressList != null && nameServerAddressList.size() > 0) {

            final RegisterBrokerRequestHeader requestHeader = new RegisterBrokerRequestHeader();
            requestHeader.setBrokerAddr(brokerAddr);
            requestHeader.setBrokerId(brokerId);
            requestHeader.setBrokerName(brokerName);
            requestHeader.setClusterName(clusterName);
            requestHeader.setHaServerAddr(haServerAddr);
            requestHeader.setCompressed(compressed);

            RegisterBrokerBody requestBody = new RegisterBrokerBody();
            requestBody.setTopicConfigSerializeWrapper(topicConfigWrapper);
            requestBody.setFilterServerList(filterServerList);
            final byte[] body = requestBody.encode(compressed);
            final int bodyCrc32 = UtilAll.crc32(body);
            requestHeader.setBodyCrc32(bodyCrc32);
            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);
                            }

                            log.info("register broker[{}]to name server {} OK", brokerId, namesrvAddr);
                        } catch (Exception e) {
                            log.warn("registerBroker Exception, {}", namesrvAddr, e);
                        } finally {
                            countDownLatch.countDown();
                        }
                    }
                });
            }

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

        return registerBrokerResultList;
    }

每一个请求RocketMQ都会定义一个RequestCode，然后在服务端会对应相应的网络处理器，只需整库搜索RequestCode即可找到相应的处理逻辑。

registerBroker：

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