标签：构造方法 目标 least 有一个 sum period roc illegal fail
在rocketmq中，nameserver充当了一个配置管理者的角色，看起来好似不太重要。然而它是一个不或缺的角色，没有了它的存在，各个broker就是一盘散沙，各自为战。
所以，实际上，在rocketmq中，nameserver也是一个领导者的角色。它可以决定哪个消息存储到哪里，哪个broker干活或者上下线，在出现异常情况时，它要能够及时处理。以便让整个团队发挥应有的作用。nameserver相当于一个分布式系统的协调者。但是这个名字，是不是看起来很熟悉？请看后续！
如文章开头所说，nameserver担任的，差不多是一个系统协调者这么个角色。那么，我们知道，在分布式协调工作方面，有很多现成的组件可用。比如 zookeeper, 那么为什么还要自己搞一套nameserver出来？是为了刷存在感？
对于为什么不选择zk之类的组件实现协调者角色，初衷如何我们不得而知。但至少有几个可知答案可以做下支撑：（以zk为例）
1. zk存在大量的集群间通信；
2. zk是一个比较重的组件，而本身就作为消息中间的mq，则最好不好另外再依赖其他组件；（个人感觉）
3. zk对于数据的固化能力比较弱，配置往往受限于zk的数据格式；
总体来说，可能就是rocketmq想要做的功能在zk上不太好做，或者做起来也费劲，或者太重，索性就不要搞了。自己搞一个完全定制化的好了。事实上，rocketmq的nameserver也实现得相当简单轻量。这也是设计者的初衷吧。
一般地，一个框架级别的服务启动，还是有些复杂的，那样的话，我们懒得去看其具体过程。但前面说了，nameserver实现得非常轻量级，所以，其启动也就相当简单。所以，我们可以快速一览其过程。
整个nameserver的启动类是 org.apache.rocketmq.namesrv.NamesrvStartup, 工作过程大致如下：
// 入口main public static void main(String[] args) { main0(args); } public static NamesrvController main0(String[] args) { try { // 创建本服务的核心控制器, 解析各种配置参数，默认值之类的 NamesrvController controller = createNamesrvController(args); // 开启服务, 如打开 start(controller); String tip = "The Name Server boot success. serializeType=" + RemotingCommand.getSerializeTypeConfigInThisServer(); log.info(tip); System.out.printf("%s%n", tip); return controller; } catch (Throwable e) { e.printStackTrace(); System.exit(-1); } return null; }
所以整个启动过程，基本就是一个 Controller 搞定了，你说不简单吗？额，也许不一定！整个创建 Controller 的过程就是解析参数的过程，有兴趣可以打开如下代码看看：
public static NamesrvController createNamesrvController(String[] args) throws IOException, JoranException { System.setProperty(RemotingCommand.REMOTING_VERSION_KEY, Integer.toString(MQVersion.CURRENT_VERSION)); //PackageConflictDetect.detectFastjson(); Options options = ServerUtil.buildCommandlineOptions(new Options()); commandLine = ServerUtil.parseCmdLine("mqnamesrv", args, buildCommandlineOptions(options), new PosixParser()); if (null == commandLine) { System.exit(-1); return null; } final NamesrvConfig namesrvConfig = new NamesrvConfig(); final NettyServerConfig nettyServerConfig = new NettyServerConfig(); nettyServerConfig.setListenPort(9876); // -c xx.properties 用于指定配置文件，优先级较低 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(); } } // -p 仅为打印查看启动参数 if (commandLine.hasOption(‘p‘)) { InternalLogger console = InternalLoggerFactory.getLogger(LoggerName.NAMESRV_CONSOLE_NAME); MixAll.printObjectProperties(console, namesrvConfig); MixAll.printObjectProperties(console, nettyServerConfig); System.exit(0); } MixAll.properties2Object(ServerUtil.commandLine2Properties(commandLine), namesrvConfig); if (null == namesrvConfig.getRocketmqHome()) { System.out.printf("Please set the %s variable in your environment to match the location of the RocketMQ installation%n", MixAll.ROCKETMQ_HOME_ENV); System.exit(-2); } LoggerContext lc = (LoggerContext) LoggerFactory.getILoggerFactory(); JoranConfigurator configurator = new JoranConfigurator(); configurator.setContext(lc); lc.reset(); configurator.doConfigure(namesrvConfig.getRocketmqHome() + "/conf/logback_namesrv.xml"); log = InternalLoggerFactory.getLogger(LoggerName.NAMESRV_LOGGER_NAME); MixAll.printObjectProperties(log, namesrvConfig); MixAll.printObjectProperties(log, nettyServerConfig); // 将配置参数传入controller构造实例 final NamesrvController controller = new NamesrvController(namesrvConfig, nettyServerConfig); // remember all configs to prevent discard controller.getConfiguration().registerConfig(properties); return controller; } // Controller 构造方法 // org.apache.rocketmq.namesrv.NamesrvController#NamesrvController public NamesrvController(NamesrvConfig namesrvConfig, NettyServerConfig nettyServerConfig) { this.namesrvConfig = namesrvConfig; this.nettyServerConfig = nettyServerConfig; this.kvConfigManager = new KVConfigManager(this); this.routeInfoManager = new RouteInfoManager(); this.brokerHousekeepingService = new BrokerHousekeepingService(this); this.configuration = new Configuration( log, this.namesrvConfig, this.nettyServerConfig ); this.configuration.setStorePathFromConfig(this.namesrvConfig, "configStorePath"); } // org.apache.rocketmq.common.Configuration#registerConfig /** * register config properties * * @return the current Configuration object */ public Configuration registerConfig(Properties extProperties) { if (extProperties == null) { return this; } try { readWriteLock.writeLock().lockInterruptibly(); try { merge(extProperties, this.allConfigs); } finally { readWriteLock.writeLock().unlock(); } } catch (InterruptedException e) { log.error("register lock error. {}" + extProperties); } return this; }
接下来，我们主要来看看这start()过程到底如何，复杂性必然都在这里了。
// org.apache.rocketmq.namesrv.NamesrvStartup#start public static NamesrvController start(final NamesrvController controller) throws Exception { if (null == controller) { throw new IllegalArgumentException("NamesrvController is null"); } // 初始化controller各环境，如果失败，则退出启动 boolean initResult = controller.initialize(); if (!initResult) { controller.shutdown(); System.exit(-3); } // 注册一个关闭钩子 Runtime.getRuntime().addShutdownHook(new ShutdownHookThread(log, new Callable<Void>() { @Override public Void call() throws Exception { controller.shutdown(); return null; } })); // 核心start()方法 controller.start(); return controller; } // org.apache.rocketmq.namesrv.NamesrvController#initialize public boolean initialize() { this.kvConfigManager.load(); this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.brokerHousekeepingService); this.remotingExecutor = Executors.newFixedThreadPool(nettyServerConfig.getServerWorkerThreads(), new ThreadFactoryImpl("RemotingExecutorThread_")); // 注册处理器 this.registerProcessor(); // 启动后台扫描线程，扫描掉线的broker this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() { @Override public void run() { NamesrvController.this.routeInfoManager.scanNotActiveBroker(); } }, 5, 10, TimeUnit.SECONDS); // 打印日志定时任务 this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() { @Override public void run() { NamesrvController.this.kvConfigManager.printAllPeriodically(); } }, 1, 10, TimeUnit.MINUTES); if (TlsSystemConfig.tlsMode != TlsMode.DISABLED) { // Register a listener to reload SslContext try { fileWatchService = new FileWatchService( new String[] { TlsSystemConfig.tlsServerCertPath, TlsSystemConfig.tlsServerKeyPath, TlsSystemConfig.tlsServerTrustCertPath }, new FileWatchService.Listener() { boolean certChanged, keyChanged = false; @Override public void onChanged(String path) { if (path.equals(TlsSystemConfig.tlsServerTrustCertPath)) { log.info("The trust certificate changed, reload the ssl context"); reloadServerSslContext(); } if (path.equals(TlsSystemConfig.tlsServerCertPath)) { certChanged = true; } if (path.equals(TlsSystemConfig.tlsServerKeyPath)) { keyChanged = true; } if (certChanged && keyChanged) { log.info("The certificate and private key changed, reload the ssl context"); certChanged = keyChanged = false; reloadServerSslContext(); } } private void reloadServerSslContext() { ((NettyRemotingServer) remotingServer).loadSslContext(); } }); } catch (Exception e) { log.warn("FileWatchService created error, can‘t load the certificate dynamically"); } } // no false return true; } private void registerProcessor() { if (namesrvConfig.isClusterTest()) { this.remotingServer.registerDefaultProcessor(new ClusterTestRequestProcessor(this, namesrvConfig.getProductEnvName()), this.remotingExecutor); } else { // 只会有一个处理器处理业务 this.remotingServer.registerDefaultProcessor(new DefaultRequestProcessor(this), this.remotingExecutor); } } // 初始化完成后，接下来是 start() 方法 // org.apache.rocketmq.namesrv.NamesrvController#start public void start() throws Exception { // 开启后台端口服务，nameserver可连接 this.remotingServer.start(); // 文件检测线程 if (this.fileWatchService != null) { this.fileWatchService.start(); } }
可见，controller的启动过程也非常简单，就是设置好各初始实例，注册处理器，然后将tcp端口打开，即可。其中端口服务是使用netty作为通信组件，其操作完全遵从netty编程范式。可自行查阅。
@Override public void start() { this.defaultEventExecutorGroup = new DefaultEventExecutorGroup( nettyServerConfig.getServerWorkerThreads(), new ThreadFactory() { private AtomicInteger threadIndex = new AtomicInteger(0); @Override public Thread newThread(Runnable r) { return new Thread(r, "NettyServerCodecThread_" + this.threadIndex.incrementAndGet()); } }); prepareSharableHandlers(); ServerBootstrap childHandler = this.serverBootstrap.group(this.eventLoopGroupBoss, this.eventLoopGroupSelector) .channel(useEpoll() ? EpollServerSocketChannel.class : NioServerSocketChannel.class) .option(ChannelOption.SO_BACKLOG, 1024) .option(ChannelOption.SO_REUSEADDR, true) .option(ChannelOption.SO_KEEPALIVE, false) .childOption(ChannelOption.TCP_NODELAY, true) .childOption(ChannelOption.SO_SNDBUF, nettyServerConfig.getServerSocketSndBufSize()) .childOption(ChannelOption.SO_RCVBUF, nettyServerConfig.getServerSocketRcvBufSize()) .localAddress(new InetSocketAddress(this.nettyServerConfig.getListenPort())) .childHandler(new ChannelInitializer<SocketChannel>() { @Override public void initChannel(SocketChannel ch) throws Exception { ch.pipeline() .addLast(defaultEventExecutorGroup, HANDSHAKE_HANDLER_NAME, handshakeHandler) .addLast(defaultEventExecutorGroup, encoder, new NettyDecoder(), new IdleStateHandler(0, 0, nettyServerConfig.getServerChannelMaxIdleTimeSeconds()), connectionManageHandler, serverHandler ); } }); if (nettyServerConfig.isServerPooledByteBufAllocatorEnable()) { childHandler.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT); } try { ChannelFuture sync = this.serverBootstrap.bind().sync(); InetSocketAddress addr = (InetSocketAddress) sync.channel().localAddress(); this.port = addr.getPort(); } catch (InterruptedException e1) { throw new RuntimeException("this.serverBootstrap.bind().sync() InterruptedException", e1); } if (this.channelEventListener != null) { this.nettyEventExecutor.start(); } this.timer.scheduleAtFixedRate(new TimerTask() { @Override public void run() { try { NettyRemotingServer.this.scanResponseTable(); } catch (Throwable e) { log.error("scanResponseTable exception", e); } } }, 1000 * 3, 1000); }
至此，nameserver的启动流程就完成了，果然是轻量级。至于其提供什么样的服务，我们下一节再讲。
因nameserver和broker一样，都共用了remoting模块的代码，即都依赖于netty的handler处理机制。所以其处理器入口都是一样的。反正最终都是找到对应的processor, 然后处理业务即可。此处，nameserver只会提供一个默认的处理器，即DefaultRequestProcessor。所以，只需了解其processRequest()即可知nameserver的整体能力了。
// org.apache.rocketmq.namesrv.processor.DefaultRequestProcessor#processRequest @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，这种操作一般是在broker启动的时候进行请求 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); } // 下线broker case RequestCode.UNREGISTER_BROKER: return this.unregisterBroker(ctx, request); // 获取路由信息，即哪个topic存在于哪些broker上，哪些messageQueue在哪里等 case RequestCode.GET_ROUTEINFO_BY_TOPIC: return this.getRouteInfoByTopic(ctx, request); case RequestCode.GET_BROKER_CLUSTER_INFO: return this.getBrokerClusterInfo(ctx, request); case RequestCode.WIPE_WRITE_PERM_OF_BROKER: return this.wipeWritePermOfBroker(ctx, request); case RequestCode.GET_ALL_TOPIC_LIST_FROM_NAMESERVER: return getAllTopicListFromNameserver(ctx, request); case RequestCode.DELETE_TOPIC_IN_NAMESRV: return deleteTopicInNamesrv(ctx, request); case RequestCode.GET_KVLIST_BY_NAMESPACE: return this.getKVListByNamespace(ctx, request); case RequestCode.GET_TOPICS_BY_CLUSTER: return this.getTopicsByCluster(ctx, request); 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); case RequestCode.UPDATE_NAMESRV_CONFIG: return this.updateConfig(ctx, request); case RequestCode.GET_NAMESRV_CONFIG: return this.getConfig(ctx, request); default: break; } return null; }
以上就是整个nameserver提供的服务列表了，也没啥注释，见字如悟吧，我们也不想过多纠缠。但总体上，其处理的业务类型并不多，主要有三类：
1. 配置信息kv的操作；
2. broker上下线管理操作；
3. topic路由信息管理服务；
各自实现当然是按照业务处理，本无需多说，但为了解概要，我们还是挑一个重点来说说吧：broker的上线处理注册：
// 为保持前沿起见，咱们以高版本服务展开思路（即版本大于3.0.11） public RemotingCommand registerBrokerWithFilterServer(ChannelHandlerContext ctx, RemotingCommand request) throws RemotingCommandException { final RemotingCommand response = RemotingCommand.createResponseCommand(RegisterBrokerResponseHeader.class); final RegisterBrokerResponseHeader responseHeader = (RegisterBrokerResponseHeader) response.readCustomHeader(); final RegisterBrokerRequestHeader requestHeader = (RegisterBrokerRequestHeader) request.decodeCommandCustomHeader(RegisterBrokerRequestHeader.class); if (!checksum(ctx, request, requestHeader)) { response.setCode(ResponseCode.SYSTEM_ERROR); response.setRemark("crc32 not match"); return response; } RegisterBrokerBody registerBrokerBody = new RegisterBrokerBody(); if (request.getBody() != null) { try { registerBrokerBody = RegisterBrokerBody.decode(request.getBody(), requestHeader.isCompressed()); } catch (Exception e) { throw new RemotingCommandException("Failed to decode RegisterBrokerBody", e); } } else { registerBrokerBody.getTopicConfigSerializeWrapper().getDataVersion().setCounter(new AtomicLong(0)); registerBrokerBody.getTopicConfigSerializeWrapper().getDataVersion().setTimestamp(0); } // 重点实现: registerBroker RegisterBrokerResult result = this.namesrvController.getRouteInfoManager().registerBroker( requestHeader.getClusterName(), requestHeader.getBrokerAddr(), requestHeader.getBrokerName(), requestHeader.getBrokerId(), requestHeader.getHaServerAddr(), registerBrokerBody.getTopicConfigSerializeWrapper(), registerBrokerBody.getFilterServerList(), ctx.channel()); responseHeader.setHaServerAddr(result.getHaServerAddr()); responseHeader.setMasterAddr(result.getMasterAddr()); byte[] jsonValue = this.namesrvController.getKvConfigManager().getKVListByNamespace(NamesrvUtil.NAMESPACE_ORDER_TOPIC_CONFIG); response.setBody(jsonValue); response.setCode(ResponseCode.SUCCESS); response.setRemark(null); return response; } // org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager#registerBroker 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 { // 上锁更新各表数据 this.lock.writeLock().lockInterruptibly(); // 集群名表 Set<String> brokerNames = this.clusterAddrTable.get(clusterName); if (null == brokerNames) { brokerNames = new HashSet<String>(); this.clusterAddrTable.put(clusterName, brokerNames); } brokerNames.add(brokerName); boolean registerFirst = false; // broker详细信息表 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); } 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 brokerAddrTable 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); if (null != topicConfigWrapper && MixAll.MASTER_ID == brokerId) { if (this.isBrokerTopicConfigChanged(brokerAddr, topicConfigWrapper.getDataVersion()) || registerFirst) { // 首次注册或者topic变更，则更新topic信息 ConcurrentMap<String, TopicConfig> tcTable = topicConfigWrapper.getTopicConfigTable(); if (tcTable != null) { for (Map.Entry<String, TopicConfig> entry : tcTable.entrySet()) { this.createAndUpdateQueueData(brokerName, entry.getValue()); } } } } // 存活的broker信息表 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); } if (filterServerList != null) { if (filterServerList.isEmpty()) { this.filterServerTable.remove(brokerAddr); } else { this.filterServerTable.put(brokerAddr, filterServerList); } } // slave节点注册需绑定masterAddr 返回 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; }
好吧，是不是很抽象。没关系，能知道大概意思就行了。大体上就是broker上线了，nameserver需要知道这些事，要把这信息加入到各表项中，以备将来使用。具体理解我们应该要从业务性质出发才能透彻。反正就和咱们平时写业务代码并无二致。
nameserver除了有注册broker的核心作用外，还有一个非常核心的作用就是，为各消费者或生产者提供各topic信息所在位置。这个位置决定了数据如何存储以及如何访问问题，只要这个决策出问题，则整个集群的可靠性就无法保证了。所以，这个点需要我们深入理解下。
在kafka中，其存储策略是和shard强相关的，一个topic分配了多少shard就决定了它可以存储到几个机器节点上，即kafka是以shard作为粒度分配存储的。
但rocketmq中则不太一样，类似的概念有：topic是最外层的存储，而messageQueue则是内一层的存储，它是否是按照topic存储或者按照msgQueue存在呢？实际上，在官方文档中，已经描述清楚了： Broker 在实际部署过程中对应一台服务器，每个 Broker 可以存储多个Topic的消息，每个Topic的消息也可以分片存储于不同的 Broker。Message Queue 用于存储消息的物理地址，每个Topic中的消息地址存储于多个 Message Queue 中。
即rocketmq中是以message queue作为最细粒度的存储的，实际上这基本无悬念，因为分布式存储需要。（试想以topic为存储粒度会带来多少问题就知道了）
那么，它又是如何划分哪个message queue存储在哪里的呢？
// RequestCode.GET_ROUTEINFO_BY_TOPIC public RemotingCommand getRouteInfoByTopic(ChannelHandlerContext ctx, RemotingCommand request) throws RemotingCommandException { final RemotingCommand response = RemotingCommand.createResponseCommand(null); final GetRouteInfoRequestHeader requestHeader = (GetRouteInfoRequestHeader) request.decodeCommandCustomHeader(GetRouteInfoRequestHeader.class); // 获取topic路由信息 TopicRouteData topicRouteData = this.namesrvController.getRouteInfoManager().pickupTopicRouteData(requestHeader.getTopic()); if (topicRouteData != null) { // 顺序消费配置 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; } // org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager#pickupTopicRouteData public TopicRouteData pickupTopicRouteData(final String topic) { TopicRouteData topicRouteData = new TopicRouteData(); boolean foundQueueData = false; boolean foundBrokerData = false; Set<String> brokerNameSet = new HashSet<String>(); List<BrokerData> brokerDataList = new LinkedList<BrokerData>(); topicRouteData.setBrokerDatas(brokerDataList); HashMap<String, List<String>> filterServerMap = new HashMap<String, List<String>>(); topicRouteData.setFilterServerTable(filterServerMap); try { try { this.lock.readLock().lockInterruptibly(); // 获取所有topic的messageQueue信息 List<QueueData> queueDataList = this.topicQueueTable.get(topic); if (queueDataList != null) { topicRouteData.setQueueDatas(queueDataList); foundQueueData = true; Iterator<QueueData> it = queueDataList.iterator(); while (it.hasNext()) { QueueData qd = it.next(); brokerNameSet.add(qd.getBrokerName()); } // 根据brokerName, 查找broker信息，如果没找到说明该broker可能已经下线，不能算在路由信息内 for (String brokerName : brokerNameSet) { BrokerData brokerData = this.brokerAddrTable.get(brokerName); if (null != brokerData) { BrokerData brokerDataClone = new BrokerData(brokerData.getCluster(), brokerData.getBrokerName(), (HashMap<Long, String>) brokerData .getBrokerAddrs().clone()); brokerDataList.add(brokerDataClone); // 只要找到一个broker就可以进行路由处理 foundBrokerData = true; for (final String brokerAddr : brokerDataClone.getBrokerAddrs().values()) { List<String> filterServerList = this.filterServerTable.get(brokerAddr); filterServerMap.put(brokerAddr, filterServerList); } } } } } finally { this.lock.readLock().unlock(); } } catch (Exception e) { log.error("pickupTopicRouteData Exception", e); } log.debug("pickupTopicRouteData {} {}", topic, topicRouteData); // 只有队列信息和broker信息都找到时，整个路由信息才可返回 if (foundBrokerData && foundQueueData) { return topicRouteData; } return null; } // QueueData 作为路由信息的重要组成部分，其数据结构如下 public class QueueData implements Comparable<QueueData> { private String brokerName; private int readQueueNums; private int writeQueueNums; private int perm; private int topicSynFlag; ... } // brokerData 数据结构如下 public class BrokerData implements Comparable<BrokerData> { private String cluster; private String brokerName; private HashMap<Long/* brokerId */, String/* broker address */> brokerAddrs; ... }
ok, 从上面的实现中，我们可以看到，查找路由信息，是根据topic进行查找的。而topic信息保存在 topicQueueTable 中。这里有个重要点是，整个路由查找过程，居然的queueId是无关的，那么它又是如何定位queueId所在的位置呢？另外，这个topicQueTable里的数据又是何时维护的呢？
首先，对于topicQueueTable的维护，是在broker注册和解注册时维护的，这很好理解。
// 也就前面看到的broker为master节点时的 createAndUpdateQueueData() private void createAndUpdateQueueData(final String brokerName, final TopicConfig topicConfig) { QueueData queueData = new QueueData(); queueData.setBrokerName(brokerName); queueData.setWriteQueueNums(topicConfig.getWriteQueueNums()); queueData.setReadQueueNums(topicConfig.getReadQueueNums()); queueData.setPerm(topicConfig.getPerm()); queueData.setTopicSynFlag(topicConfig.getTopicSysFlag()); List<QueueData> queueDataList = this.topicQueueTable.get(topicConfig.getTopicName()); // topic的首个broker 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 { boolean addNewOne = true; Iterator<QueueData> it = queueDataList.iterator(); // 添加一个broker while (it.hasNext()) { QueueData qd = it.next(); if (qd.getBrokerName().equals(brokerName)) { if (qd.equals(queueData)) { addNewOne = false; } else { log.info("topic changed, {} OLD: {} NEW: {}", topicConfig.getTopicName(), qd, queueData); it.remove(); } } } if (addNewOne) { queueDataList.add(queueData); } } }
但针对queueId又是何时进行处理的呢？看起来nameserver不得而知。
事实上，数据发送到哪个broker或从哪个broker上进行数据消费，是由各客户端根据策略决定的。比如在producer中是这样处理的：
// org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#sendDefaultImpl private SendResult sendDefaultImpl( Message msg, final CommunicationMode communicationMode, final SendCallback sendCallback, final long timeout ) throws MQClientException, RemotingException, MQBrokerException, InterruptedException { this.makeSureStateOK(); Validators.checkMessage(msg, this.defaultMQProducer); final long invokeID = random.nextLong(); long beginTimestampFirst = System.currentTimeMillis(); long beginTimestampPrev = beginTimestampFirst; long endTimestamp = beginTimestampFirst; // 此处即是nameserver返回的路由信息，即可用的broker列表 TopicPublishInfo topicPublishInfo = this.tryToFindTopicPublishInfo(msg.getTopic()); if (topicPublishInfo != null && topicPublishInfo.ok()) { boolean callTimeout = false; MessageQueue mq = null; Exception exception = null; SendResult sendResult = null; int timesTotal = communicationMode == CommunicationMode.SYNC ? 1 + this.defaultMQProducer.getRetryTimesWhenSendFailed() : 1; int times = 0; String[] brokersSent = new String[timesTotal]; for (; times < timesTotal; times++) { // 首次进入时，只是选择一个队列发送 String lastBrokerName = null == mq ? null : mq.getBrokerName(); MessageQueue mqSelected = this.selectOneMessageQueue(topicPublishInfo, lastBrokerName); if (mqSelected != null) { mq = mqSelected; brokersSent[times] = mq.getBrokerName(); try { beginTimestampPrev = System.currentTimeMillis(); if (times > 0) { //Reset topic with namespace during resend. msg.setTopic(this.defaultMQProducer.withNamespace(msg.getTopic())); } long costTime = beginTimestampPrev - beginTimestampFirst; if (timeout < costTime) { callTimeout = true; break; } // 向选择出来的messageQueue 发送消息数据 sendResult = this.sendKernelImpl(msg, mq, communicationMode, sendCallback, topicPublishInfo, timeout - costTime); endTimestamp = System.currentTimeMillis(); this.updateFaultItem(mq.getBrokerName(), endTimestamp - beginTimestampPrev, false); switch (communicationMode) { case ASYNC: return null; case ONEWAY: return null; case SYNC: if (sendResult.getSendStatus() != SendStatus.SEND_OK) { if (this.defaultMQProducer.isRetryAnotherBrokerWhenNotStoreOK()) { continue; } } return sendResult; default: break; } } catch (RemotingException e) ... } // org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#selectOneMessageQueue public MessageQueue selectOneMessageQueue(final TopicPublishInfo tpInfo, final String lastBrokerName) { return this.mqFaultStrategy.selectOneMessageQueue(tpInfo, lastBrokerName); } // org.apache.rocketmq.client.latency.MQFaultStrategy#selectOneMessageQueue public MessageQueue selectOneMessageQueue(final TopicPublishInfo tpInfo, final String lastBrokerName) { // 容错处理，不影响策略理解 if (this.sendLatencyFaultEnable) { try { int index = tpInfo.getSendWhichQueue().getAndIncrement(); for (int i = 0; i < tpInfo.getMessageQueueList().size(); i++) { int pos = Math.abs(index++) % tpInfo.getMessageQueueList().size(); if (pos < 0) pos = 0; MessageQueue mq = tpInfo.getMessageQueueList().get(pos); if (latencyFaultTolerance.isAvailable(mq.getBrokerName())) { if (null == lastBrokerName || mq.getBrokerName().equals(lastBrokerName)) return mq; } } final String notBestBroker = latencyFaultTolerance.pickOneAtLeast(); int writeQueueNums = tpInfo.getQueueIdByBroker(notBestBroker); if (writeQueueNums > 0) { final MessageQueue mq = tpInfo.selectOneMessageQueue(); if (notBestBroker != null) { mq.setBrokerName(notBestBroker); mq.setQueueId(tpInfo.getSendWhichQueue().getAndIncrement() % writeQueueNums); } return mq; } else { latencyFaultTolerance.remove(notBestBroker); } } catch (Exception e) { log.error("Error occurred when selecting message queue", e); } return tpInfo.selectOneMessageQueue(); } return tpInfo.selectOneMessageQueue(lastBrokerName); } // org.apache.rocketmq.client.impl.producer.TopicPublishInfo#selectOneMessageQueue // 直接使用轮询的方式选择一个队列 public MessageQueue selectOneMessageQueue(final String lastBrokerName) { if (lastBrokerName == null) { // 任意选择一个messageQueue作为发送目标 return selectOneMessageQueue(); } else { int index = this.sendWhichQueue.getAndIncrement(); // 最大尝试n次获取不一样的MQueue, 如仍然获取不到，则随便选择一个即可 for (int i = 0; i < this.messageQueueList.size(); i++) { int pos = Math.abs(index++) % this.messageQueueList.size(); if (pos < 0) pos = 0; MessageQueue mq = this.messageQueueList.get(pos); if (!mq.getBrokerName().equals(lastBrokerName)) { return mq; } } return selectOneMessageQueue(); } }
好了，通过上面的描述，我们大概知道了，一个消息要发送往消息server时，首先会根据topic找到所有可用的broker列表（nameserver提供），然后根据一个所谓策略选择一个MessageQueue，最后向这个MessageQueue发送数据即可。所以，这个MessageQueue是非常重要的，我们来看下其数据结构：
// org.apache.rocketmq.common.message.MessageQueue public class MessageQueue implements Comparable<MessageQueue>, Serializable { private static final long serialVersionUID = 6191200464116433425L; private String topic; private String brokerName; private int queueId; ... }
这是非常之简洁啊，仅有主要的三个核心：topic(主题),brokerName(broker标识),queueId(队列id)。
前面提到的客户端策略，会选择一个MessageQueue, 即会得到一个broker标识，对应一个queueId。所以，数据存放在哪个broker，是由客户端决定的，且存放位置未知。也就是说，rocketmq中同一个topic的数据，是散乱存放在一堆broker中的。这是和我们通常的认知有一定差距的。
这样设计有什么好处呢？好处自然是有的，比如假如其中有些broker挂掉了，那么整个集群无需经过什么再均衡策略，同样可以工作得很好，因为客户端可以直接向正常的broker发送消息即可。其他好处。。。
但是我个人觉得这样的设计，也不见得很好，比如你不能够很确定地定位到某条消息在哪个broker上，完全无规律可循。另外，如果想在单queueId上保持一定的规则，则是不可能的（也许有其他曲线救国之法）。另外，对于queueId, 只是一个系统内部的概念，实际上用户并不能指定该值。
按照上面说的，一个topic数据可能被存放在n个broker中，且以messageQueue的queueId作为单独存储。那么，到底数据存放在哪里？所说的n个broker到底指哪几个broker？每个broker上到底存放了几个queueId？这些问题如果没有搞清楚，我们就无法说清楚这玩意。
我们先来回答第1个问题，topic数据到底存放在几个broker中？回顾下前面broker的注册过程可知：
// org.apache.rocketmq.namesrv.routeinfo.RouteInfoManager#registerBroker if (null != topicConfigWrapper && MixAll.MASTER_ID == brokerId) { if (this.isBrokerTopicConfigChanged(brokerAddr, topicConfigWrapper.getDataVersion()) || registerFirst) { // 首次注册或者topic变更，则更新topic信息 ConcurrentMap<String, TopicConfig> tcTable = topicConfigWrapper.getTopicConfigTable(); if (tcTable != null) { // 遍历所有topic, 将当前新进的broker 加入到处理机器中 for (Map.Entry<String, TopicConfig> entry : tcTable.entrySet()) { this.createAndUpdateQueueData(brokerName, entry.getValue()); } } } }
看完这段，我们就明白了，原来所谓的n个broker可处理topic信息，实际上指的是所有broker啊！好吧，咱也不懂为啥这么干同，反正就是这么干了，topic可能分布在所有broker机器上。至于具体哪一台，你猜啊！
接下来我们看第二个问题，一个broker到底存储了几个queueId的数据？实际上，我们稍微想想前面的实现，broker是指所有的broker，如果所有broker都是一样的配置，那么是不是应该让每个broker都存储所有queueId呢？（尽管没啥依据，还是可以想想的嘛）
rocketmq的各客户端（生产者、消费者）每次向服务器发送生产或消费请求时，都可能向nameserver请求拉取路由信息，但这些信息从我们前面调查的结果来看，并不包含queueId信息。那么，后续又是如何转换为queueId的呢？实际上，就是在拉取了nameserver的路由信息之后，本地再做一次分配就可以了：
// 更新topic路由信息 // org.apache.rocketmq.client.impl.producer.DefaultMQProducerImpl#tryToFindTopicPublishInfo private TopicPublishInfo tryToFindTopicPublishInfo(final String topic) { TopicPublishInfo topicPublishInfo = this.topicPublishInfoTable.get(topic); if (null == topicPublishInfo || !topicPublishInfo.ok()) { this.topicPublishInfoTable.putIfAbsent(topic, new TopicPublishInfo()); this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic); topicPublishInfo = this.topicPublishInfoTable.get(topic); } if (topicPublishInfo.isHaveTopicRouterInfo() || topicPublishInfo.ok()) { return topicPublishInfo; } else { // 从nameserver拉取路由数据 this.mQClientFactory.updateTopicRouteInfoFromNameServer(topic, true, this.defaultMQProducer); topicPublishInfo = this.topicPublishInfoTable.get(topic); return topicPublishInfo; } } // org.apache.rocketmq.client.impl.factory.MQClientInstance#updateTopicRouteInfoFromNameServer 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) { topicRouteData = this.mQClientAPIImpl.getDefaultTopicRouteInfoFromNameServer(defaultMQProducer.getCreateTopicKey(), 1000 * 3); if (topicRouteData != null) { for (QueueData data : topicRouteData.getQueueDatas()) { int queueNums = Math.min(defaultMQProducer.getDefaultTopicQueueNums(), data.getReadQueueNums()); data.setReadQueueNums(queueNums); data.setWriteQueueNums(queueNums); } } } else { topicRouteData = this.mQClientAPIImpl.getTopicRouteInfoFromNameServer(topic, 1000 * 3); } if (topicRouteData != null) { TopicRouteData old = this.topicRouteTable.get(topic); boolean changed = topicRouteDataIsChange(old, topicRouteData); if (!changed) { changed = this.isNeedUpdateTopicRouteInfo(topic); } else { log.info("the topic[{}] route info changed, old[{}] ,new[{}]", topic, old, topicRouteData); } if (changed) { TopicRouteData cloneTopicRouteData = topicRouteData.cloneTopicRouteData(); for (BrokerData bd : topicRouteData.getBrokerDatas()) { this.brokerAddrTable.put(bd.getBrokerName(), bd.getBrokerAddrs()); } // Update Pub info { // 为每个broker分配queueId TopicPublishInfo publishInfo = topicRouteData2TopicPublishInfo(topic, topicRouteData); publishInfo.setHaveTopicRouterInfo(true); Iterator<Entry<String, MQProducerInner>> it = this.producerTable.entrySet().iterator(); while (it.hasNext()) { Entry<String, MQProducerInner> entry = it.next(); MQProducerInner impl = entry.getValue(); if (impl != null) { impl.updateTopicPublishInfo(topic, publishInfo); } } } // Update sub info { Set<MessageQueue> subscribeInfo = topicRouteData2TopicSubscribeInfo(topic, topicRouteData); Iterator<Entry<String, MQConsumerInner>> it = this.consumerTable.entrySet().iterator(); while (it.hasNext()) { Entry<String, MQConsumerInner> entry = it.next(); MQConsumerInner impl = entry.getValue(); if (impl != null) { impl.updateTopicSubscribeInfo(topic, subscribeInfo); } } } log.info("topicRouteTable.put. Topic = {}, TopicRouteData[{}]", topic, cloneTopicRouteData); this.topicRouteTable.put(topic, cloneTopicRouteData); return true; } } else { log.warn("updateTopicRouteInfoFromNameServer, getTopicRouteInfoFromNameServer return null, Topic: {}", topic); } } catch (MQClientException e) { if (!topic.startsWith(MixAll.RETRY_GROUP_TOPIC_PREFIX)) { log.warn("updateTopicRouteInfoFromNameServer Exception", e); } } catch (RemotingException e) { log.error("updateTopicRouteInfoFromNameServer Exception", e); throw new IllegalStateException(e); } finally { this.lockNamesrv.unlock(); } } else { log.warn("updateTopicRouteInfoFromNameServer tryLock timeout {}ms", LOCK_TIMEOUT_MILLIS); } } catch (InterruptedException e) { log.warn("updateTopicRouteInfoFromNameServer Exception", e); } return false; }
生产者分配queueId的实现如下：
// org.apache.rocketmq.client.impl.factory.MQClientInstance#topicRouteData2TopicPublishInfo public static TopicPublishInfo topicRouteData2TopicPublishInfo(final String topic, final TopicRouteData route) { TopicPublishInfo info = new TopicPublishInfo(); info.setTopicRouteData(route); // 为每个broker指定queueId的分配情况（最大queueId） // 这样的配置不知道累不累 if (route.getOrderTopicConf() != null && route.getOrderTopicConf().length() > 0) { String[] brokers = route.getOrderTopicConf().split(";"); for (String broker : brokers) { String[] item = broker.split(":"); int nums = Integer.parseInt(item[1]); for (int i = 0; i < nums; i++) { MessageQueue mq = new MessageQueue(topic, item[0], i); info.getMessageQueueList().add(mq); } } info.setOrderTopic(true); } else { List<QueueData> qds = route.getQueueDatas(); Collections.sort(qds); for (QueueData qd : qds) { if (PermName.isWriteable(qd.getPerm())) { BrokerData brokerData = null; for (BrokerData bd : route.getBrokerDatas()) { if (bd.getBrokerName().equals(qd.getBrokerName())) { brokerData = bd; break; } } // 还是有broker无法处理queue哦 if (null == brokerData) { continue; } // 非master节点不能接受写请求 if (!brokerData.getBrokerAddrs().containsKey(MixAll.MASTER_ID)) { continue; } // 根据 writeQueueNums 数量，要求该broker接受所有小于该值的queueId for (int i = 0; i < qd.getWriteQueueNums(); i++) { MessageQueue mq = new MessageQueue(topic, qd.getBrokerName(), i); info.getMessageQueueList().add(mq); } } } info.setOrderTopic(false); } return info; }
可以看出，生产者对应的broker中，负责写的broker只能是master节点，负责所有小于writeQueueNums的数据存储。（如果所有broker配置一样，则相当于所有broker都存储所有queueId），所以，这存储关系，可能是理不清楚了。
我们再来看看消费者是如何对应queueId的呢？
// org.apache.rocketmq.client.impl.factory.MQClientInstance#topicRouteData2TopicSubscribeInfo public static Set<MessageQueue> topicRouteData2TopicSubscribeInfo(final String topic, final TopicRouteData route) { Set<MessageQueue> mqList = new HashSet<MessageQueue>(); List<QueueData> qds = route.getQueueDatas(); for (QueueData qd : qds) { if (PermName.isReadable(qd.getPerm())) { // 可读取broker上对应的所有小于readQueueNums 的队列 for (int i = 0; i < qd.getReadQueueNums(); i++) { MessageQueue mq = new MessageQueue(topic, qd.getBrokerName(), i); mqList.add(mq); } } } return mqList; }
原理和生产者差不多，就是通过一个 readQueueNums 来限定读取的队列数，基本上就是等于所有队列了，原因可能是原本数据就存储了所有queueId，如果消费者不读取，又该谁来读取呢。
好了，到此我们总算厘清了整个rocketmq的消息存储定位方式了。总结一句话就是：任何节点都可能有任意topic的任意queueId数据。这结果，不禁又让我有一种千头万绪的感觉！
以上仅是一些正常的rocketmq数据存储的实现，只能算是皮毛。事实上，分布式系统中一个非常重要的能力是容错，这需要我们后续再聊。
RocketMQ(六)：nameserver队列存储定位解析
标签：构造方法 目标 least 有一个 sum period roc illegal fail
原文地址：https://www.cnblogs.com/yougewe/p/14128845.html
