RocketMQ源码分析-NameServer

架构设计

消息中间件的设计思路一般是基于主题订阅发布的机制，消息生产者（Producer）发送某一个主题到消息服务器，消息服务器负责将消息持久化存储，消息消费者（Consumer）订阅该兴趣的主题，消息服务器根据订阅信息（路由信息）将消息推送到消费者（Push模式）或者消费者主动向消息服务器拉去（Pull模式），从而实现消息生产者与消息消费者解耦。为了避免消息服务器的单点故障导致的整个系统瘫痪，通常会部署多台消息服务器共同承担消息的存储。那消息生产者如何知道消息要发送到哪台消息服务器呢？如果某一台消息服务器宕机了，那么消息生产者如何在不重启服务情况下感知呢？
NameServer就是为了解决以上问题设计的。

Broker消息服务器在启动的时向所有NameServer注册，消息生产者（Producer）在发送消息时之前先从NameServer获取Broker服务器地址列表，然后根据负载均衡算法从列表中选择一台服务器进行发送。NameServer与每台Broker保持长连接，并间隔30S检测Broker是否存活，如果检测到Broker宕机，则从路由注册表中删除。但是路由变化不会马上通知消息生产者。这样设计的目的是为了降低NameServer实现的复杂度，在消息发送端提供容错机制保证消息发送的可用性。

NameServer本身的高可用是通过部署多台NameServer来实现，但彼此之间不通讯，也就是NameServer服务器之间在某一个时刻的数据并不完全相同，但这对消息发送并不会造成任何影响，这也是NameServer设计的一个亮点，总之，RocketMQ设计追求简单高效。

NameServer的作用其实和Zookeeper是有点像的，NameServer的设计要比Zookeeper的设计要更加简单，RocketMQ其实也可以使用Zookeeper替代NameServer，但是RocketMQ为了不于第三方中间件耦合，自己做了一套NameServer的简化版的Zookeeper

NameServer启动流程

步骤一

解析配置文件，填充NameServerConfig、NettyServerConfig属性值，并创建NamesrvController

NamesrvController#createNamesrvController

//创建NamesrvConfig
final NamesrvConfig namesrvConfig = new NamesrvConfig();
//创建NettyServerConfig
final NettyServerConfig nettyServerConfig = new NettyServerConfig();
//设置启动端口号
nettyServerConfig.setListenPort(9876);
//解析启动-c参数
if (commandLine.hasOption('c')) {
     
    String file = commandLine.getOptionValue('c');
    if (file != null) {
     
        InputStream in = new BufferedInputStream(new FileInputStream(file));
        properties = new Properties();
        properties.load(in);
        MixAll.properties2Object(properties, namesrvConfig);
        MixAll.properties2Object(properties, nettyServerConfig);

        namesrvConfig.setConfigStorePath(file);

        System.out.printf("load config properties file OK, %s%n", file);
        in.close();
    }
}
//解析启动-p参数
if (commandLine.hasOption('p')) {
     
    InternalLogger console = InternalLoggerFactory.getLogger(LoggerName.NAMESRV_CONSOLE_NAME);
    MixAll.printObjectProperties(console, namesrvConfig);
    MixAll.printObjectProperties(console, nettyServerConfig);
    System.exit(0);
}
//将启动参数填充到namesrvConfig,nettyServerConfig
MixAll.properties2Object(ServerUtil.commandLine2Properties(commandLine), namesrvConfig);

//创建NameServerController
final NamesrvController controller = new NamesrvController(namesrvConfig, nettyServerConfig);

NamesrvConfig属性

private String rocketmqHome = System.getProperty(MixAll.ROCKETMQ_HOME_PROPERTY, System.getenv(MixAll.ROCKETMQ_HOME_ENV));
private String kvConfigPath = System.getProperty("user.home") + File.separator + "namesrv" + File.separator + "kvConfig.json";
private String configStorePath = System.getProperty("user.home") + File.separator + "namesrv" + File.separator + "namesrv.properties";
private String productEnvName = "center";
private boolean clusterTest = false;
private boolean orderMessageEnable = false;

rocketmqHome： rocketmq主目录

kvConfig： NameServer存储KV配置属性的持久化路径

configStorePath： nameServer默认配置文件路径

orderMessageEnable： 是否支持顺序消息

NettyServerConfig属性

private int listenPort = 8888;
private int serverWorkerThreads = 8;
private int serverCallbackExecutorThreads = 0;
private int serverSelectorThreads = 3;
private int serverOnewaySemaphoreValue = 256;
private int serverAsyncSemaphoreValue = 64;
private int serverChannelMaxIdleTimeSeconds = 120;
private int serverSocketSndBufSize = NettySystemConfig.socketSndbufSize;
private int serverSocketRcvBufSize = NettySystemConfig.socketRcvbufSize;
private boolean serverPooledByteBufAllocatorEnable = true;
private boolean useEpollNativeSelector = false;

listenPort： NameServer监听端口，该值默认会被初始化为9876
serverWorkerThreads： Netty业务线程池线程个数
serverCallbackExecutorThreads： Netty public任务线程池线程个数，Netty网络设计，根据业务类型会创建不同的线程池，比如处理消息发送、消息消费、心跳检测等。如果该业务类型未注册线程池，则由public线程池执行。
serverSelectorThreads： IO线程池个数，主要是NameServer、Broker端解析请求、返回相应的线程个数，这类线程主要是处理网路请求的，解析请求包，然后转发到各个业务线程池完成具体的操作，然后将结果返回给调用方;
serverOnewaySemaphoreValue： send oneway消息请求并发读（Broker端参数）;
serverAsyncSemaphoreValue： 异步消息发送最大并发度;
serverChannelMaxIdleTimeSeconds ： 网络连接最大的空闲时间，默认120s。
serverSocketSndBufSize： 网络socket发送缓冲区大小。
serverSocketRcvBufSize： 网络接收端缓存区大小。
serverPooledByteBufAllocatorEnable： ByteBuffer是否开启缓存;
useEpollNativeSelector： 是否启用Epoll IO模型。

路由管理

NameServer的主要作用是为消息的生产者和消息消费者提供关于主题Topic的路由信息，那么NameServer需要存储路由的基础信息，还要管理Broker节点，包括路由注册、路由删除等。
路由元信息

//代码：RouteInfoManager
private final HashMap<String/* topic */, List<QueueData>> topicQueueTable;
private final HashMap<String/* brokerName */, BrokerData> brokerAddrTable;
private final HashMap<String/* clusterName */, Set<String/* brokerName */>> clusterAddrTable;
private final HashMap<String/* brokerAddr */, BrokerLiveInfo> brokerLiveTable;
private final HashMap<String/* brokerAddr */, List<String>/* Filter Server */> filterServerTable;

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

brokerAddrTable： Broker基础信息，包括brokerName、所属集群名称、主备Broker地址

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

brokerLiveTable： Broker状态信息，NameServer每次收到心跳包是会替换该信息

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

RocketMQ基于定于发布机制，一个Topic拥有多个消息队列，一个Broker为每一个主题创建4个读队列和4个写队列。多个Broker组成一个集群，集群由相同的多台Broker组成Master-Slave架构，brokerId为0代表Master，大于0为Slave。BrokerLiveInfo中的lastUpdateTimestamp存储上次收到Broker心跳包的时间。

路由注册
发送心跳包

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NameServer发送心跳信息，每隔30s向集群中所有NameServer发送心跳包，NameServer收到心跳包时会更新brokerLiveTable缓存中BrokerLiveInfo的lastUpdataTimeStamp信息，然后NameServer每隔10s扫描brokerLiveTable，如果连续120S没有收到心跳包，NameServer将移除Broker的路由信息同时关闭Socket连接。

//代码：BrokerController#start
//注册Broker信息
this.registerBrokerAll(true, false, true);
//每隔30s上报Broker信息到NameServer
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
     

    @Override
    public 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);

BrokerOuterAPI#registerBrokerAll

//获得nameServer地址信息
List<String> nameServerAddressList = this.remotingClient.getNameServerAddressList();
//遍历所有nameserver列表
if (nameServerAddressList != null && nameServerAddressList.size() > 0) {
     

    //封装请求头
    final RegisterBrokerRequestHeader requestHeader = new RegisterBrokerRequestHeader();
    requestHeader.setBrokerAddr(brokerAddr);
    requestHeader.setBrokerId(brokerId);
    requestHeader.setBrokerName(brokerName);
    requestHeader.setClusterName(clusterName);
    requestHeader.setHaServerAddr(haServerAddr);
    requestHeader.setCompressed(compressed);
	//封装请求体
    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 {
     
                    //分别向NameServer注册
                    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) {
     
    }
}

//BrokerOutAPI#registerBroke
if (oneway) {
     
    try {
     
        this.remotingClient.invokeOneway(namesrvAddr, request, timeoutMills);
    } catch (RemotingTooMuchRequestException e) {
     
        // Ignore
    }
    return null;
}
RemotingCommand response = this.remotingClient.invokeSync(namesrvAddr, request, timeoutMills);

处理心跳包

org.apache.rocketmq.namesrv.processor.DefaultRequestProcessor网路处理类解析请求类型，如果请求类型是为***REGISTER_BROKER***，则将请求转发到RouteInfoManager#regiesterBroker

//DefaultRequestProcessor#processRequest
//判断是注册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 {
     
        //注册Broker信息
	    return this.registerBroker(ctx, request);
	}

//DefaultRequestProcessor#registerBroker
RegisterBrokerResult result = this.namesrvController.getRouteInfoManager().registerBroker(
    requestHeader.getClusterName(),
    requestHeader.getBrokerAddr(),
    requestHeader.getBrokerName(),
    requestHeader.getBrokerId(),
    requestHeader.getHaServerAddr(),
    topicConfigWrapper,
    null,
    ctx.channel()
);

//RouteInfoManager#registerBroker
//维护路由信息
//加锁
this.lock.writeLock().lockInterruptibly();
//维护clusterAddrTable
Set<String> brokerNames = this.clusterAddrTable.get(clusterName);
if (null == brokerNames) {
     
    brokerNames = new HashSet<String>();
    this.clusterAddrTable.put(clusterName, brokerNames);
}
brokerNames.add(brokerName);

//维护brokerAddrTable
BrokerData brokerData = this.brokerAddrTable.get(brokerName);
//第一次注册,则创建brokerData
if (null == brokerData) {
     
    registerFirst = true;
    brokerData = new BrokerData(clusterName, brokerName, new HashMap<Long, String>());
    this.brokerAddrTable.put(brokerName, brokerData);
}
//非第一次注册,更新Broker
Map<Long, String> brokerAddrsMap = brokerData.getBrokerAddrs();
Iterator<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()) {
     
        it.remove();
    }
}
String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);
registerFirst = registerFirst || (null == oldAddr);

//维护topicQueueTable
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());
            }
        }
    }
}

//RouteInfoManager#createAndUpdateQueueData
private void createAndUpdateQueueData(final String brokerName, final TopicConfig topicConfig) {
     
    //创建QueueData
	QueueData queueData = new QueueData();
	queueData.setBrokerName(brokerName);
	queueData.setWriteQueueNums(topicConfig.getWriteQueueNums());
	queueData.setReadQueueNums(topicConfig.getReadQueueNums());
	queueData.setPerm(topicConfig.getPerm());
	queueData.setTopicSynFlag(topicConfig.getTopicSysFlag());
	//获得topicQueueTable中队列集合
	List<QueueData> queueDataList = this.topicQueueTable.get(topicConfig.getTopicName());
    //topicQueueTable为空,则直接添加queueData到队列集合
	if (null == queueDataList) {
     
	    queueDataList = new LinkedList<QueueData>();
	    queueDataList.add(queueData);
	    this.topicQueueTable.put(topicConfig.getTopicName(), queueDataList);
	    log.info("new topic registered, {} {}", topicConfig.getTopicName(), queueData);
	} else {
     
        //判断是否是新的队列
	    boolean addNewOne = true;
	    Iterator<QueueData> it = queueDataList.iterator();
	    while (it.hasNext()) {
     
	        QueueData qd = it.next();
            //如果brokerName相同,代表不是新的队列
	        if (qd.getBrokerName().equals(brokerName)) {
     
	            if (qd.equals(queueData)) {
     
	                addNewOne = false;
	        } else {
     
	                    log.info("topic changed, {} OLD: {} NEW: {}", topicConfig.getTopicName(), qd,
	                        queueData);
	                    it.remove();
	                }
	            }
	        }
		//如果是新的队列,则添加队列到queueDataList
        if (addNewOne) {
     
            queueDataList.add(queueData);
        }
    }
}

//维护brokerLiveTable
BrokerLiveInfo prevBrokerLiveInfo = this.brokerLiveTable.put(brokerAddr,new BrokerLiveInfo(
    System.currentTimeMillis(),
    topicConfigWrapper.getDataVersion(),
    channel,
    haServerAddr));
//维护filterServerList
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);
        }
    }
}

路由删除
Broker每隔30s向NameServer发送一个心跳包，心跳包包含BrokerId，Broker地址，Broker名称，Broker所属集群名称、Broker关联的FilterServer列表。但是如果Broker宕机，NameServer无法收到心跳包，此时NameServer如何来剔除这些失效的Broker呢？NameServer会每隔10s扫描brokerLiveTable状态表，如果BrokerLive的lastUpdateTimestamp的时间戳距当前时间超过120s，则认为Broker失效，移除该Broker，关闭与Broker连接，同时更新topicQueueTable、brokerAddrTable、brokerLiveTable、filterServerTable。

RocketMQ有两个触发点来删除路由信息：

• NameServer定期扫描brokerLiveTable检测上次心跳包与当前系统的时间差，如果时间超过120s，则需要移除broker。
• Broker在正常关闭的情况下，会执行unregisterBroker指令

这两种方式路由删除的方法都是一样的，就是从相关路由表中删除与该broker相关的信息。

//NamesrvController#initialize
//每隔10s扫描一次为活跃Broker
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
     

    @Override
    public void run() {
     
        NamesrvController.this.routeInfoManager.scanNotActiveBroker();
    }
}, 5, 10, TimeUnit.SECONDS);

//RouteInfoManager#scanNotActiveBroker
public void scanNotActiveBroker() {
     
    //获得brokerLiveTable
    Iterator<Entry<String, BrokerLiveInfo>> it = this.brokerLiveTable.entrySet().iterator();
    //遍历brokerLiveTable
    while (it.hasNext()) {
     
        Entry<String, BrokerLiveInfo> next = it.next();
        long last = next.getValue().getLastUpdateTimestamp();
        //如果收到心跳包的时间距当时时间是否超过120s
        if ((last + BROKER_CHANNEL_EXPIRED_TIME) < System.currentTimeMillis()) {
     
            //关闭连接
            RemotingUtil.closeChannel(next.getValue().getChannel());
            //移除broker
            it.remove();
            //维护路由表
            this.onChannelDestroy(next.getKey(), next.getValue().getChannel());
        }
    }
}

//RouteInfoManager#onChannelDestroy
//申请写锁,根据brokerAddress从brokerLiveTable和filterServerTable移除
this.lock.writeLock().lockInterruptibly();
this.brokerLiveTable.remove(brokerAddrFound);
this.filterServerTable.remove(brokerAddrFound);

//维护brokerAddrTable
String brokerNameFound = null;
boolean removeBrokerName = false;
Iterator<Entry<String, BrokerData>> itBrokerAddrTable =this.brokerAddrTable.entrySet().iterator();
//遍历brokerAddrTable
while (itBrokerAddrTable.hasNext() && (null == brokerNameFound)) {
     
    BrokerData brokerData = itBrokerAddrTable.next().getValue();
    //遍历broker地址
    Iterator<Entry<Long, String>> it = brokerData.getBrokerAddrs().entrySet().iterator();
    while (it.hasNext()) {
     
        Entry<Long, String> entry = it.next();
        Long brokerId = entry.getKey();
        String brokerAddr = entry.getValue();
        //根据broker地址移除brokerAddr
        if (brokerAddr.equals(brokerAddrFound)) {
     
            brokerNameFound = brokerData.getBrokerName();
            it.remove();
            log.info("remove brokerAddr[{}, {}] from brokerAddrTable, because channel destroyed",
                brokerId, brokerAddr);
            break;
        }
    }
	//如果当前主题只包含待移除的broker,则移除该topic
    if (brokerData.getBrokerAddrs().isEmpty()) {
     
        removeBrokerName = true;
        itBrokerAddrTable.remove();
        log.info("remove brokerName[{}] from brokerAddrTable, because channel destroyed",
            brokerData.getBrokerName());
    }
}

//维护clusterAddrTable
if (brokerNameFound != null && removeBrokerName) {
     
    Iterator<Entry<String, Set<String>>> it = this.clusterAddrTable.entrySet().iterator();
    //遍历clusterAddrTable
    while (it.hasNext()) {
     
        Entry<String, Set<String>> entry = it.next();
        //获得集群名称
        String clusterName = entry.getKey();
        //获得集群中brokerName集合
        Set<String> brokerNames = entry.getValue();
        //从brokerNames中移除brokerNameFound
        boolean removed = brokerNames.remove(brokerNameFound);
        if (removed) {
     
            log.info("remove brokerName[{}], clusterName[{}] from clusterAddrTable, because channel destroyed",
                brokerNameFound, clusterName);

            if (brokerNames.isEmpty()) {
     
                log.info("remove the clusterName[{}] from clusterAddrTable, because channel destroyed and no broker in this cluster",
                    clusterName);
                //如果集群中不包含任何broker,则移除该集群
                it.remove();
            }

            break;
        }
    }
}

//维护topicQueueTable队列
if (removeBrokerName) {
     
    //遍历topicQueueTable
    Iterator<Entry<String, List<QueueData>>> itTopicQueueTable =
        this.topicQueueTable.entrySet().iterator();
    while (itTopicQueueTable.hasNext()) {
     
        Entry<String, List<QueueData>> entry = itTopicQueueTable.next();
        //主题名称
        String topic = entry.getKey();
        //队列集合
        List<QueueData> queueDataList = entry.getValue();
		//遍历该主题队列
        Iterator<QueueData> itQueueData = queueDataList.iterator();
        while (itQueueData.hasNext()) {
     
            //从队列中移除为活跃broker信息
            QueueData queueData = itQueueData.next();
            if (queueData.getBrokerName().equals(brokerNameFound)) {
     
                itQueueData.remove();
                log.info("remove topic[{} {}], from topicQueueTable, because channel destroyed",
                    topic, queueData);
            }
        }
		//如果该topic的队列为空,则移除该topic
        if (queueDataList.isEmpty()) {
     
            itTopicQueueTable.remove();
            log.info("remove topic[{}] all queue, from topicQueueTable, because channel destroyed",
                topic);
        }
    }
}


//释放写锁
finally {
     
    this.lock.writeLock().unlock();
}

路由发现
RocketMQ路由发现是非实时的，当Topic路由出现变化后，NameServer不会主动推送给客户端，而是由客户端定时拉取主题最新的路由。

//DefaultRequestProcessor#getRouteInfoByTopic

public RemotingCommand getRouteInfoByTopic(ChannelHandlerContext ctx,
    RemotingCommand request) throws RemotingCommandException {
     
    final RemotingCommand response = RemotingCommand.createResponseCommand(null);
    final GetRouteInfoRequestHeader requestHeader =
        (GetRouteInfoRequestHeader) request.decodeCommandCustomHeader(GetRouteInfoRequestHeader.class);
	//调用RouteInfoManager的方法,从路由表topicQueueTable、brokerAddrTable、filterServerTable中分别填充TopicRouteData的List、List、filterServer
    TopicRouteData topicRouteData = this.namesrvController.getRouteInfoManager().pickupTopicRouteData(requestHeader.getTopic());
	//如果找到主题对应你的路由信息并且该主题为顺序消息，则从NameServer KVConfig中获取关于顺序消息相关的配置填充路由信息
    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;
}

总结