Name Server主要是用于管理所有的broker信息，让producer和consumer都能获取到正确的broker信息，进行业务处理。
类似于zookeeper的服务治理中心，在旧版本中使用的就是zookeeper，为什么放弃zookeeper？
- 在RocketMQ中，topic在每个master的数据是对等的，没有哪个master有全部的topic数据，所以选举是没有意义的
- NameServer与NameServer之间完全没有信息同步，所以与其依赖重量级的zookeeper，不如开发轻量级的NameServer
NameServer的启动过程
解析配置文件
入口类：NamesrvStartup
NamesrvStartup主要负责解析配置文件，创建NamesrvController
org.apache.rocketmq.namesrv.NamesrvStartup
public static void main(String[] args) {
main0(args);
}
public static NamesrvController main0(String[] args) {
try {
// 创建NamesrvController
NamesrvController controller = createNamesrvController(args);
// 调用NamesrvController的initialize，并启动netty
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;
}
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);
if (commandLine.hasOption('c')) {
// -c选项，指定配置文件路径
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();
}
}
if (commandLine.hasOption('p')) {
// -p选项 只打印系统参数，不启动，直接退出
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);
final NamesrvController controller = new NamesrvController(namesrvConfig, nettyServerConfig);
// remember all configs to prevent discard
controller.getConfiguration().registerConfig(properties);
return controller;
}初始化
NamesrvController负责NameServer的初始化，启动Netty服务端。
org.apache.rocketmq.namesrv.NamesrvController#initialize
public boolean initialize() {
// 加载kv配置
this.kvConfigManager.load();
// 创建netty服务端
this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.brokerHousekeepingService);
this.remotingExecutor =
Executors.newFixedThreadPool(nettyServerConfig.getServerWorkerThreads(), new ThreadFactoryImpl("RemotingExecutorThread_"));
// 注册默认的处理类 DefaultRequestProcessor,所有的请求均由该处理类的 processRequest 方法来处理。
this.registerProcessor();
// 每隔10s扫描一次Broker,移除不活跃的Broker
this.scheduledExecutorService.scheduleAtFixedRate(NamesrvController.this.routeInfoManager::scanNotActiveBroker, 5, 10, TimeUnit.SECONDS);
// 每隔10min打印一次KV配置
this.scheduledExecutorService.scheduleAtFixedRate(NamesrvController.this.kvConfigManager::printAllPeriodically, 1, 10, TimeUnit.MINUTES);
if (TlsSystemConfig.tlsMode != TlsMode.DISABLED) {
// Register a listener to reload SslContext
try {
// 实时监听文件的变化
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");
}
}
return true;
}启动Netty服务端。
org.apache.rocketmq.namesrv.NamesrvController#start
public void start() throws Exception {
// 启动Netty服务端
this.remotingServer.start();
if (this.fileWatchService != null) {
this.fileWatchService.start();
}
}broker注册与发现
NameServer使用以下结构来存储信息：
private final HashMap<String/* topic */, Map<String /* brokerName */ , 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每次收到心跳包时会替换该信息
- filterServerTable：Broker上的FilterServer列表，用于类模式消息过滤。
NameServer的实现基于内存，NameServer并不会持久化路由信息，持久化的重任是交给Broker来完成。
处理broker的注册请求
如果收到REGISTER_BROKER请求，那么最终会调用到RouteInfoManager.registerBroker。注册完成后，返回给Broker端主用Broker的地址和主用Broker的HA服务地址。
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 {
this.lock.writeLock().lockInterruptibly();
/**
* broker-a.properties
*
* brokerClusterName=DefaultCluster
* brokerName=broker-a
* brokerId=0
*/
// clusterAddrTable key为集群名，value为broker集合
// 若Broker集群名字不在该Map变量中，则初始化一个Set集合，将brokerName存入该Set集合中，
// 然后以clusterName为key值，该Set集合为values值存入此clusterAddrTable中
Set<String> brokerNames = this.clusterAddrTable.computeIfAbsent(clusterName, k -> new HashSet<>());
brokerNames.add(brokerName);
boolean registerFirst = false;
// 同一个BrokerName下面可以有多个不同BrokerId的Broker存在
// 表示一个BrokerName有多个Broker 存在，通过BrokerId来区分主备
BrokerData brokerData = this.brokerAddrTable.get(brokerName);
if (null == brokerData) {
// 第一次注册
registerFirst = true;
brokerData = new BrokerData(clusterName, brokerName, new HashMap<>());
// brokerAddrTable维护Broker基础信息，
// key为brokerName，value包括brokerName、所属集群名称、主备Broker地址
this.brokerAddrTable.put(brokerName, brokerData);
}
// key为brokerId, value为broker address
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()) {
// brokerId变了直接移除，可能是slave升级为master
log.debug("remove entry {} from brokerData", item);
it.remove();
}
}
String oldAddr = brokerData.getBrokerAddrs().put(brokerId, brokerAddr);
if (MixAll.MASTER_ID == brokerId) {
log.info("cluster [{}] brokerName [{}] master address change from {} to {}",
brokerData.getCluster(), brokerData.getBrokerName(), oldAddr, brokerAddr);
}
registerFirst = registerFirst || (null == oldAddr);
// 若Broker的注册请求消息中topic的配置不为空，并且该Broker是主用（即brokerId=0）
if (null != topicConfigWrapper
&& MixAll.MASTER_ID == brokerId) {
// 则根据NameServer存储的Broker版本信息来判断是否需要更新NameServer端的topic配置信息
if (this.isBrokerTopicConfigChanged(brokerAddr, topicConfigWrapper.getDataVersion())
|| registerFirst) {
ConcurrentMap<String, TopicConfig> tcTable =
topicConfigWrapper.getTopicConfigTable();
if (tcTable != null) {
for (Map.Entry<String, TopicConfig> entry : tcTable.entrySet()) {
// 更新broker的队列信息
this.createAndUpdateQueueData(brokerName, entry.getValue());
}
}
}
}
// brokerLiveTable存储broker的心跳信息，key为broker地址，value存储心跳的时间
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);
}
// 对于filterServerList不为空的， 以broker地址为key值存入
if (filterServerList != null) {
if (filterServerList.isEmpty()) {
this.filterServerTable.remove(brokerAddr);
} else {
this.filterServerTable.put(brokerAddr, filterServerList);
}
}
// 找到该BrokerName下面的主Broker（BrokerId=0）
if (MixAll.MASTER_ID != brokerId) {
String masterAddr = brokerData.getBrokerAddrs().get(MixAll.MASTER_ID);
if (masterAddr != null) {
// 根据主Broker地址从brokerLiveTable中获取BrokerLiveInfo对象，取该对象的HaServerAddr值
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;
}根据Topic获取Broker信息和topic配置信息
接收到GET_ROUTEINTO_BY_TOPIC请求之后，间接调用了RouteInfoManager.pickupTopicRouteData方法来获取Broker和topic信息。
public TopicRouteData pickupTopicRouteData(final String topic) {
TopicRouteData topicRouteData = new TopicRouteData();
boolean foundQueueData = false;
boolean foundBrokerData = false;
Set<String> brokerNameSet = new HashSet<>();
List<BrokerData> brokerDataList = new LinkedList<>();
topicRouteData.setBrokerDatas(brokerDataList);
HashMap<String, List<String>> filterServerMap = new HashMap<>();
topicRouteData.setFilterServerTable(filterServerMap);
try {
try {
this.lock.readLock().lockInterruptibly();
// topicQueueTable key为topic，value为queueDataMap
// queueDataMap key为brokerName，value为队列信息
Map<String, QueueData> queueDataMap = this.topicQueueTable.get(topic);
if (queueDataMap != null) {
topicRouteData.setQueueDatas(new ArrayList<>(queueDataMap.values()));
foundQueueData = true;
brokerNameSet.addAll(queueDataMap.keySet());
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);
foundBrokerData = true;
// skip if filter server table is empty
if (!filterServerTable.isEmpty()) {
for (final String brokerAddr : brokerDataClone.getBrokerAddrs().values()) {
List<String> filterServerList = this.filterServerTable.get(brokerAddr);
// only add filter server list when not null
if (filterServerList != null) {
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;
}因为Broker每隔30s向NameServer发送一个心跳包，这个操作每次都会更新Broker的状态，但同时生产者发送消息时也需要Broker的状态，要进行频繁的读取操作。所以这个地方就有一个矛盾，Broker的状态会被经常性的更新，同时也会被更加频繁的读取。这里如何提高并发，尤其是生产者进行消息发送时的并发，所以这里使用了读写锁机制（针对读多写少的场景）。
NameServer每收到一个心跳包，将更新brokerLiveTable中关于Broker的状态信息以及路由表(topicQueueTable、brokerAddrTable、brokerLiveTable、filterServerTable)。更新上述路由表使用了锁粒度较少的读写锁，允许多个消息发送者（Producer)并发读保证消息发送时的高并发。但同一时刻NameServer只处理一个Broker心跳包，多个心跳包请求串行执行，这也是读写锁经典使用场景。
路由剔除机制
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，都是从相关路由表中删除与该broker相关的信息。
public int scanNotActiveBroker() {
int removeCount = 0;
Iterator<Entry<String, BrokerLiveInfo>> it = tis.brokerLiveTable.entrySet().iterator();
while (it.hasNext()) {
Entry<String, BrokerLiveInfo> next = it.next();
long last = next.getValue().getLastUpdateTimestamp();
// 超过120s未发送心跳包，剔除
if ((last + BROKER_CHANNEL_EXPIRED_TIME) < System.currentTimeMillis()) {
RemotingUtil.closeChannel(next.getValue().getChannel());
it.remove();
log.warn("The broker channel expired, {} {}ms", next.getKey(), BROKER_CHANNEL_EXPIRED_TIME);
this.onChannelDestroy(next.getKey(), next.getValue().getChannel());
removeCount++;
}
}
return removeCount;
}
