RocketMQ架构的四个核心
rocketmq_architecture_1.png
Producer Cluster
消息的发送者，需要去NameServer去取到对应Topic的信息去建立连接并发送消息到指定Broker
Consumer Cluster
消息的消费者，需要去NameServer去取到对应Topic的信息去建立连接到指定的Broker并取得消息去消费
Broker
实际消息的接收站，消息的存储地，过滤功能等。启动会向NameServer注册自己。
NameServer
RocketMQ的注册中心，支持Broker的动态注册与发现，保存元数据，干啥都要先找他去做路由。
NameSrv -
在真实环境中，如果有生产者，消费者加入或者掉线，Broker扩容或掉线等各种异常场景，NameSrv的协调管理能力正是用于解决此类场景。但相较之下，NameSrv比大多数分布式协调服务或注册中心又轻量的多。比如ZK、Eureka都会在Node之间做同步，而NameSrv被设计成无状态的，每个NameSrv节点互相不通信。
NameSrv 启动流程
入口
public static NamesrvController main0(String[] args) {
try {
NamesrvController controller = createNamesrvController(args);
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;
}
createNamesrvController
public static NamesrvController createNamesrvController(String[] args) throws IOException, JoranException {
// 省略部分
final NamesrvConfig namesrvConfig = new NamesrvConfig();
final NettyServerConfig nettyServerConfig = new NettyServerConfig();
nettyServerConfig.setListenPort(9876);
// 如果启动命令含有 c 代表指定了配置文件 如 -c /home/rocketmq/conf/namesrv.properties
if (commandLine.hasOption('c')) {
String file = commandLine.getOptionValue('c');
if (file != null) {
// 读文件
InputStream in = new BufferedInputStream(new FileInputStream(file));
properties = new Properties();
properties.load(in);
// 把配置写入namesrvConfig和nettyServerConfig中
MixAll.properties2Object(properties, namesrvConfig);
MixAll.properties2Object(properties, nettyServerConfig);
namesrvConfig.setConfigStorePath(file);
System.out.printf("load config properties file OK, %s%n", file);
in.close();
}
}
// 省略部分
// 日志配置
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);
// 把namesrvConfig和nettyServerConfig构建一个NamesrvController
final NamesrvController controller = new NamesrvController(namesrvConfig, nettyServerConfig);
// remember all configs to prevent discard
controller.getConfiguration().registerConfig(properties);
return controller;
}
NamesrvController的参数和他的构造函数
NamesrvController的参数
// namesrv配置信息
private final NamesrvConfig namesrvConfig;
// nettyServer配置信息
private final NettyServerConfig nettyServerConfig;
// 单个线程的定时调度线程池
private final ScheduledExecutorService scheduledExecutorService = Executors.newSingleThreadScheduledExecutor(new ThreadFactoryImpl(
"NSScheduledThread"));
// 键值对管理
private final KVConfigManager kvConfigManager;
// 路由信息管理
private final RouteInfoManager routeInfoManager;
// 实际启动的netty server
private RemotingServer remotingServer;
// broker管理
private BrokerHousekeepingService brokerHousekeepingService;
// 固定大小的线程池
private ExecutorService remotingExecutor;
// 配置类
private Configuration configuration;
// 暂不知道
private FileWatchService fileWatchService;
可以看到NamesrvController类包含了很多信息，如有一个NettyServer和相关的配置，有键值对管理，有路由信息管理，有broker管理，有自己的配置。
NamesrvController的构造器
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");
}
至此，NamesrvController已实例化完毕，返回入口再执行start。
启动 controller
public static NamesrvController start(final NamesrvController controller) throws Exception {
if (null == controller) {
throw new IllegalArgumentException("NamesrvController is null");
}
// 1. 初始化controller
boolean initResult = controller.initialize();
if (!initResult) {
controller.shutdown();
System.exit(-3);
}
// 2. 注册JVM钩子函数，在JVM进程关闭之前，把用到的线程池先关闭
Runtime.getRuntime().addShutdownHook(new ShutdownHookThread(log, new Callable() {
@Override
public Void call() throws Exception {
controller.shutdown();
return null;
}
}));
// 3. 启用controller，其实就是启动netty server
controller.start();
return controller;
}
本质上NameServer是一个tcp server，启动后用于接收来自broker,C,P的请求并作出处理。
初始化
public boolean initialize() {
this.kvConfigManager.load();
// 创建netty server
this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.brokerHousekeepingService);
// 创建线程池，默认8个线程，最后丢给netty server使用
this.remotingExecutor =
Executors.newFixedThreadPool(nettyServerConfig.getServerWorkerThreads(), new ThreadFactoryImpl("RemotingExecutorThread_"));
// 为remotingServer绑定processor, 实际就是用来处理NettyServer接收到的请求
this.registerProcessor();
// 扫描不活跃的broker
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
NamesrvController.this.routeInfoManager.scanNotActiveBroker();
}
}, 5, 10, TimeUnit.SECONDS);
// 打配置
this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
NamesrvController.this.kvConfigManager.printAllPeriodically();
}
}, 1, 10, TimeUnit.MINUTES);
// 非主线省略
return true;
}
NameServer启动的流程可被简单归类于以下几个步骤 -
- 读配置，分发在NameServer和Netty的配置中
- 用配置构建NamesrvController实例
- 初始化NamesrvController
- 启动NamesrvController中的netty server用于接收请求，响应请求
至此，NameSrv已经成功启动了NettyServer，现在NameSrv是一个可以被生产者，Broker，消费者连接的一个状态了，并可以源源不断的处理他们发过来的请求。在this.registerProcessor();这一行代码中，也为NettyServer配置了具体的业务处理器。我们后面将在DefaultRequestProcessor中去探索其可以实现哪些功能。
NameSrv的核心数据结构
从上文的扫描不活跃的broker来初探NameSrv的核心数据结构
public void scanNotActiveBroker() {
Iterator> it = this.brokerLiveTable.entrySet().iterator();
// 遍历存活broker map
while (it.hasNext()) {
Entry next = it.next();
// 得到上一次更新时间
long last = next.getValue().getLastUpdateTimestamp();
// 2分钟没发心跳
if ((last + BROKER_CHANNEL_EXPIRED_TIME) < System.currentTimeMillis()) {
// 关闭channel
RemotingUtil.closeChannel(next.getValue().getChannel());
// 移出map
it.remove();
log.warn("The broker channel expired, {} {}ms", next.getKey(), BROKER_CHANNEL_EXPIRED_TIME);
this.onChannelDestroy(next.getKey(), next.getValue().getChannel());
}
}
}
brokerLiveTable是什么？从上文中看是一个维护每个Broker与NameSrv存活关系集合。NameSrv靠着一次次的接收心跳请求来判断这些Broker有没有失活。
private final HashMap> topicQueueTable;
private final HashMap brokerAddrTable;
private final HashMap brokerLiveTable;
private final HashMap/* Filter Server */> filterServerTable;
这些就是NameSrv的核心存储结构
可以从两方面来理解，其最终都是为了拿到某个broker的地址去建立连接或将broker安置到哪个Map中。
- 第一种是由topic去
topicQueueTable中拿到brokerName再去brokerAddrTable去拿到broker的地址信息。这是能猜测到的生产者去NameSrv拿broker地址的一种场景。 - 第二种是由集群名去
clusterAddrTable去拿到此集群下的brokerName。经常发生在注册broker。 -
brokerLiveTable用于保持brokerAddr的心跳状态，以定期移除不存活的broker。 -
filterServerTable这里暂不讨论
我们下面也将根据以上2种较为常用的场景对这些功能进行分析，也可以看到NameSrv是如何基于以上几个Map做出各种功能。
namesrv_maps.jpg
NameSrv的功能
NameSrv所支持的功能都在org.apache.rocketmq.namesrv.processor.DefaultRequestProcessor#processRequest方法的switch中。其主要功能是负责处理netty接收到的请求的，根据请求的类型分别执行不同的操作。我们挑RequestCode.REGISTER_BROKER和RequestCode.GET_ROUTEINFO_BY_TOPIC来看看。
路由注册
public RegisterBrokerResult registerBroker(
final String clusterName,
final String brokerAddr,
final String brokerName,
final long brokerId,
final String haServerAddr,
final TopicConfigSerializeWrapper topicConfigWrapper,
final List filterServerList,
final Channel channel) {
RegisterBrokerResult result = new RegisterBrokerResult();
try {
try {
this.lock.writeLock().lockInterruptibly();
// 根据集群名拿到集群下的所有brokerName
Set brokerNames = this.clusterAddrTable.get(clusterName);
// 如果不存在，则创建，把集群名，brokerName进行映射
if (null == brokerNames) {
brokerNames = new HashSet();
this.clusterAddrTable.put(clusterName, brokerNames);
}
// 把新注册的brokerName丢到集群table里
brokerNames.add(brokerName);
boolean registerFirst = false;
// 再根据brokerName去拿到broker的详细信息里查
BrokerData brokerData = this.brokerAddrTable.get(brokerName);
// 如果找不到对应的brokerData数据，则证明是第一次注册
if (null == brokerData) {
registerFirst = true;
// 新建brokerData并放入brokerAddrTable
brokerData = new BrokerData(clusterName, brokerName, new HashMap());
this.brokerAddrTable.put(brokerName, brokerData);
}
// 一个brokerName对应的BrokerData可能对应多个broker地址
Map 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> it = brokerAddrsMap.entrySet().iterator();
while (it.hasNext()) {
Entry item = it.next();
// 此broker的地址之前就在里面了，但此次的brokerId如发生变化，则代表主从发生了变化，移除
if (null != brokerAddr && brokerAddr.equals(item.getValue()) && brokerId != item.getKey()) {
it.remove();
}
}
// 放入新的并返回旧的，如果不存在会返回null
String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);
// oldAddr的值就能确定是不是第一次注册
registerFirst = registerFirst || (null == oldAddr);
// 如果是master节点
if (null != topicConfigWrapper
&& MixAll.MASTER_ID == brokerId) {
// 如果version不一样或是第一次注册
if (this.isBrokerTopicConfigChanged(brokerAddr, topicConfigWrapper.getDataVersion())
|| registerFirst) {
ConcurrentMap tcTable =
topicConfigWrapper.getTopicConfigTable();
if (tcTable != null) {
// 创建或更新queueData
for (Map.Entry entry : tcTable.entrySet()) {
this.createAndUpdateQueueData(brokerName, entry.getValue());
}
}
}
}
// 填充broker状态表，以便心跳检测
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);
}
}
// 如果不是master节点，则把master节点的地址放到haServer和masterAddr中
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;
}
我们将注册broker概括为以下几步
- 先把本次注册的broker信息加到
clusterAddrTable中，意为本集群下多了一个broker - 然后把broker信息注册到
brokerAddrTable中，这一步可能发生主从变化等 - 在
topicQueueTable中创建或更新队列数据 - 在
brokerLiveTable中维护本次broker的心跳信息 - 如果不是Master节点，则返回Master节点地址
路由发现
其实看过路由注册之后，八九不离十就能猜到路由发现可能是从topicQueueTable取到broker的信息，然后再去brokerAddrTable去获取每个broker的详细信息。源码也证实了这一点：
public TopicRouteData pickupTopicRouteData(final String topic) {
TopicRouteData topicRouteData = new TopicRouteData();
boolean foundQueueData = false;
boolean foundBrokerData = false;
Set brokerNameSet = new HashSet();
List brokerDataList = new LinkedList();
topicRouteData.setBrokerDatas(brokerDataList);
HashMap> filterServerMap = new HashMap>();
topicRouteData.setFilterServerTable(filterServerMap);
try {
try {
this.lock.readLock().lockInterruptibly();
List queueDataList = this.topicQueueTable.get(topic);
if (queueDataList != null) {
// topic队列元信息集合
topicRouteData.setQueueDatas(queueDataList);
foundQueueData = true;
Iterator it = queueDataList.iterator();
while (it.hasNext()) {
QueueData qd = it.next();
brokerNameSet.add(qd.getBrokerName());
}
for (String brokerName : brokerNameSet) {
BrokerData brokerData = this.brokerAddrTable.get(brokerName);
if (null != brokerData) {
BrokerData brokerDataClone = new BrokerData(brokerData.getCluster(), brokerData.getBrokerName(), (HashMap) brokerData
.getBrokerAddrs().clone());
// broker的元数据集合
brokerDataList.add(brokerDataClone);
foundBrokerData = true;
for (final String brokerAddr : brokerDataClone.getBrokerAddrs().values()) {
List 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);
if (foundBrokerData && foundQueueData) {
return topicRouteData;
}
return null;
}
总结
理解了NameSrv的核心数据结构的用处和他们的层级关系，就变相的理解了NameSrv的作用场景。从Processor上看，每个请求对应的处理皆是对这几个Map进行 一些信息的提取和维护。