RocketMQ(六)：nameserver队列存储定位解析
2024-10-21 04:14:13
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！
1. 为什么会有nameserver？
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。
2. nameserver的启动流程解析
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。
3. nameserver 业务处理框架
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。
4. topic存储位置策略
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。
5. MessageQueue到底存在哪里？
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。
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