一、簡述

這篇內(nèi)容主要講述RocketMQ的NameSrv的啟動流程，通過它的啟動，也能了解到NameSrv是干什么的，僅此而已，不做過多深入。

二、Namesrv模塊結(jié)構(gòu)及流程簡要說明

namesrv模塊代碼結(jié)構(gòu)

三、NamesrvStartup.java

該類的結(jié)構(gòu)圖如下：

NamesrvStartup.java

main -> main0 -> createNamesrvController -> start

1、createNamesrvController實例化

首先會通過createNamesrvController()方法實例化一個NamesrvController（這個類其實是核心的啟動類），這個方法做了一件事：

• a：讀取command line的參數(shù)并解析
  (如果用idea，可以在啟動類的Edit Configuration中通過Program Arguement來指定）
  如果帶有 -c path，則會加載path指定的配置文件，并結(jié)合默認(rèn)的配置，實例化NamesrvConfig及NettyServerConfig，這兩個配置類是 NamesrvController 的 Field，進(jìn)而實例化一個 NamesrvController，源碼如下：

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')) {
            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')) {
            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;
    }

如果有 -p，則會打印出所有配置，并退出，就是讓你看看配置了啥玩意兒，類似如下的輸出：

15:55:16.265 [main] INFO  RocketmqNamesrvConsole - rocketmqHome=E:\idealab\rocketmq
15:55:16.274 [main] INFO  RocketmqNamesrvConsole - kvConfigPath=C:\Users\asd\namesrv\kvConfig.json
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - configStorePath=C:\Users\asd\namesrv\namesrv.properties
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - productEnvName=center
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - clusterTest=false
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - orderMessageEnable=false
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - listenPort=9876
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverWorkerThreads=8
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverCallbackExecutorThreads=0
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverSelectorThreads=3
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverOnewaySemaphoreValue=256
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverAsyncSemaphoreValue=64
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverChannelMaxIdleTimeSeconds=120
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverSocketSndBufSize=65535
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverSocketRcvBufSize=65535
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - serverPooledByteBufAllocatorEnable=true
15:55:16.275 [main] INFO  RocketmqNamesrvConsole - useEpollNativeSelector=false

2、start（）啟動

這個方法，主要做了3件事情

• a 初始化配置 controller.initialize();
  這個初始化做了很多事情：
  加載kvConfig.json配置，目前不知道是干啥的，后續(xù)補(bǔ)充
  實例化一個 RemotingServer（NettyRemotingServer）
  啟動定時任務(wù)，檢查非活動的broker ：scanNotActiveBroker
  啟動定時任務(wù)，定期輸出 configTable 的內(nèi)容
  如果沒有禁用TSL加密，則實例化一個 FileWatchService

• b 添加一個關(guān)閉的hook：Runtime.getRuntime().addShutdownHook**

• c 啟動，啟動netty server，啟動TSL加密服務(wù)？
  RemotingServer.start()
  同時會啟動一個定時任務(wù)，定期檢查失效的鏈接
  FileWatchService.start()

源碼如下：

 public static NamesrvController start(final NamesrvController controller) throws Exception {

        if (null == controller) {
            throw new IllegalArgumentException("NamesrvController is null");
        }

        /*
            這個是非常重要的初始化方法
         */
        boolean initResult = controller.initialize();
        if (!initResult) {
            controller.shutdown();
            System.exit(-3);
        }

        Runtime.getRuntime().addShutdownHook(new ShutdownHookThread(log, new Callable<Void>() {
            @Override
            public Void call() throws Exception {
                controller.shutdown();
                return null;
            }
        }));

        controller.start();

        return controller;
    }