NameServer启动流程

小知识，大挑战！本文正在参与“程序员必备小知识”创作活动

1NameServer启动流程

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 指定属性配置文件位置
        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    属性名=属性值
        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;
}

第一步：解析配置文件，填充NamesrvConfig NettyServerConfig属性值

第二步：启动属性创建NamesrvController实例，并初始化实例，NamesrvController实例为NameServer核心控制器

NamesrvController的initialize方法：

/**
 * 初始化
 * @return
 */
public boolean initialize() {

    //加载kv配置
    this.kvConfigManager.load();

    //创建nettyServer网络处理对象
    this.remotingServer = new NettyRemotingServer(this.nettyServerConfig, this.brokerHousekeepingService);

    //开启定时任务 每隔10s扫描一次Broker 移除不活跃的Broker
    this.remotingExecutor =
        Executors.newFixedThreadPool(nettyServerConfig.getServerWorkerThreads(), new ThreadFactoryImpl("RemotingExecutorThread_"));

    this.registerProcessor();

    this.scheduledExecutorService.scheduleAtFixedRate(new Runnable() {

        @Override
        public void run() {
            NamesrvController.this.routeInfoManager.scanNotActiveBroker();
        }
    }, 5, 10, TimeUnit.SECONDS);

    //开启定时任务 每隔10分钟打印一次kv配置
    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");
        }
    }

    return true;
}

加载KV配置，创建NettyServer网络处理对象，然后开启两个定时任务，在RocketMQ中此类定时任务叫做心跳检测

• 定时任务1：NameServer每隔10s扫描一次Broker，移除不活跃的Broker
• 定时任务2：NameServer每隔10分钟打印一次KV配置

第三步：然后注册JVM钩子函数并启动服务器，一边监听Broker、消息生产者的网络请求。

//注册钩子函数
Runtime.getRuntime().addShutdownHook(new ShutdownHookThread(log, new Callable<Void>() {
    @Override
    public Void call() throws Exception {
        //释放资源
        controller.shutdown();
        return null;
    }
}));

优雅停机方式就是注册一个JVM钩子函数，在JVM进程关闭之前，先将线程池关闭，及时释放资源。