RocketMQ原理学习-- Name Server

Name Server作为RocketMQ的一个组件，其作用就是一个注册中心，用于管理Broker相关的一些信息，生产者和消费者可以从Name Server中获取Broker中相关的Topic信息等，Name Server可以单台部署也可以多台部署，相互之间不存在联系。

Name Server主要有以下两个功能：

维护一份Broker信息(集群名称、Broker名称及相关地址信息)，Broker在启动后会将自身信息注册到Name Server中
维护每个Topic相关的信息，Broker心跳时会将自身的topic提交到Name Server，生产者在发送消息时会根据Topic名称获取Broker的列表，消费者在监听Topic时也会根据Topic名称从Name Server中获取相关Broker的信息。

Name Server主要在RouteInfoManager中维护了以下几个列表(通过读写锁来实现线程安全操作)：

//每个Topic的列表信息
private final HashMap<String/* topic */, List<QueueData>> topicQueueTable;
//每个Broker的地址列表
private final HashMap<String/* brokerName */, BrokerData> brokerAddrTable;
//集群名称对应的Broker名称
private final HashMap<String/* clusterName */, Set<String/* brokerName */>> clusterAddrTable;
//每个broker地址信息
private final HashMap<String/* brokerAddr */, BrokerLiveInfo> brokerLiveTable;
//每个broker地址相关的过滤器信息
private final HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;

Name Server 启动的时序图

接下来我们通过分析源码简单了解一下：

1、请求处理器DefaultRequestProcessor：

在DefaultRequestProcessor中提供processRequest方法，会根据请求中的RequestCode值调用不同的处理操作。

	@Override
    public RemotingCommand processRequest(ChannelHandlerContext ctx,
        RemotingCommand request) throws RemotingCommandException {

        if (ctx != null) {
            log.debug("receive request, {} {} {}",
                request.getCode(),
                RemotingHelper.parseChannelRemoteAddr(ctx.channel()),
                request);
        }

        switch (request.getCode()) {
            case RequestCode.PUT_KV_CONFIG:
                return this.putKVConfig(ctx, request);
            case RequestCode.GET_KV_CONFIG:
                return this.getKVConfig(ctx, request);
            case RequestCode.DELETE_KV_CONFIG:
                return this.deleteKVConfig(ctx, request);
            case RequestCode.QUERY_DATA_VERSION:
                return queryBrokerTopicConfig(ctx, request);
			//注册Broker信息
            case RequestCode.REGISTER_BROKER:
                Version brokerVersion = MQVersion.value2Version(request.getVersion());
                if (brokerVersion.ordinal() >= MQVersion.Version.V3_0_11.ordinal()) {
                    return this.registerBrokerWithFilterServer(ctx, request);
                } else {
                    return this.registerBroker(ctx, request);
                }
			//删除Broker信息
            case RequestCode.UNREGISTER_BROKER:
                return this.unregisterBroker(ctx, request);
			//获取Topic信息
            case RequestCode.GET_ROUTEINTO_BY_TOPIC:
                return this.getRouteInfoByTopic(ctx, request);
			//获取Broker的机器信息
            case RequestCode.GET_BROKER_CLUSTER_INFO:
                return this.getBrokerClusterInfo(ctx, request);
            case RequestCode.WIPE_WRITE_PERM_OF_BROKER:
                return this.wipeWritePermOfBroker(ctx, request);
			//获取所有Topic信息
            case RequestCode.GET_ALL_TOPIC_LIST_FROM_NAMESERVER:
                return getAllTopicListFromNameserver(ctx, request);
			//删除Topic
            case RequestCode.DELETE_TOPIC_IN_NAMESRV:
                return deleteTopicInNamesrv(ctx, request);
			//通过命名空间获取配置信息
            case RequestCode.GET_KVLIST_BY_NAMESPACE:
                return this.getKVListByNamespace(ctx, request);
			//获取Topic信息
            case RequestCode.GET_TOPICS_BY_CLUSTER:
                return this.getTopicsByCluster(ctx, request);
			//获取系统Topic
            case RequestCode.GET_SYSTEM_TOPIC_LIST_FROM_NS:
                return this.getSystemTopicListFromNs(ctx, request);
            case RequestCode.GET_UNIT_TOPIC_LIST:
                return this.getUnitTopicList(ctx, request);
            case RequestCode.GET_HAS_UNIT_SUB_TOPIC_LIST:
                return this.getHasUnitSubTopicList(ctx, request);
            case RequestCode.GET_HAS_UNIT_SUB_UNUNIT_TOPIC_LIST:
                return this.getHasUnitSubUnUnitTopicList(ctx, request);
			//更新NameServer的配置
            case RequestCode.UPDATE_NAMESRV_CONFIG:
                return this.updateConfig(ctx, request);
			//获取Name Server的配置信息
            case RequestCode.GET_NAMESRV_CONFIG:
                return this.getConfig(ctx, request);
            default:
                break;
        }
        return null;
    }

2、Broker注册：

（1）Broker注册请求头信息

（2）Broker注册请求体信息

根据请求头及请求体中的信息将相关Broker和Topic信息添加到RouteInfoManager中。

3、Producer查询Topic信息：

（1）Producer请求头信息

根据Topic名称TopicA-Test从 RouteInfoManager的topicQueueTable中获取相关队列信息。

调用代码如下：

public RemotingCommand getRouteInfoByTopic(ChannelHandlerContext ctx,
        RemotingCommand request) throws RemotingCommandException {
        final RemotingCommand response = RemotingCommand.createResponseCommand(null);
        final GetRouteInfoRequestHeader requestHeader =
            (GetRouteInfoRequestHeader) request.decodeCommandCustomHeader(GetRouteInfoRequestHeader.class);

        TopicRouteData topicRouteData = this.namesrvController.getRouteInfoManager().pickupTopicRouteData(requestHeader.getTopic());

        if (topicRouteData != null) {
            if (this.namesrvController.getNamesrvConfig().isOrderMessageEnable()) {
                String orderTopicConf =
                    this.namesrvController.getKvConfigManager().getKVConfig(NamesrvUtil.NAMESPACE_ORDER_TOPIC_CONFIG,
                        requestHeader.getTopic());
                topicRouteData.setOrderTopicConf(orderTopicConf);
            }

            byte[] content = topicRouteData.encode();
            response.setBody(content);
            response.setCode(ResponseCode.SUCCESS);
            response.setRemark(null);
            return response;
        }

        response.setCode(ResponseCode.TOPIC_NOT_EXIST);
        response.setRemark("No topic route info in name server for the topic: " + requestHeader.getTopic()
            + FAQUrl.suggestTodo(FAQUrl.APPLY_TOPIC_URL));
        return response;
    }

RocketMQ原理学习-- Name Server

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