NameServer负责MQ消息的路由。生产者发送消息前，先从NameServer获取broker列表，然后根据负载均衡算法，找到broker发送消息。

NameServer本地启动流程

查看mqnameserv.sh脚本，我们看下核心的启动方法

sh ${ROCKETMQ_HOME}/bin/runserver.sh org.apache.rocketmq.namesrv.NamesrvStartup $@

找到对应的类，启动即可启动本地mq NameServer，不过鉴于本地需要校验NameServer的安装home路径，所以我们直接修改代码：

直接右键启动，报错

Please set the %s variable in your environment to match the location of the RocketMQ installation%n

查看对应的错误源码：

   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);
        }

我们看到MQ会加载校验对应的RockeMQHome，那么我们可以通过以下几个方式设置：

1. 更改源码，写死地址信息
2. 通过vm options -Drocketmq.home.dir=/Users/jinglongjun/programe/rocketMQ/release/rocketmq-4.5.2 来指定。
3. 设置环境变量 ROCKETMQ_HOME

NameServer 配置文件加载

NamesrvController#createNamesrvController方法

        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));
                .....
            }
        }

        if (commandLine.hasOption('p')) {
           ....
        }

通过如上方式我们可以看到不同的加载配置文件的方式。
最终填充两个核心配置：

• NamesrvConfig
• NettyServerConfig

NamesrvConfig的配置信息如下

public class NamesrvConfig {
  
    private String rocketmqHome = System.getProperty(MixAll.ROCKETMQ_HOME_PROPERTY, System.getenv(MixAll.ROCKETMQ_HOME_ENV));
    private String kvConfigPath = System.getProperty("user.home") + File.separator + "namesrv" + File.separator + "kvConfig.json";
    private String configStorePath = System.getProperty("user.home") + File.separator + "namesrv" + File.separator + "namesrv.properties";
    private String productEnvName = "center";
    private boolean clusterTest = false;
    private boolean orderMessageEnable = false;

NettyServerConfig 的配置信息如下：

public class NettyServerConfig implements Cloneable {
    private int listenPort = 8888;
    private int serverWorkerThreads = 8;
    private int serverCallbackExecutorThreads = 0;
    private int serverSelectorThreads = 3;
    private int serverOnewaySemaphoreValue = 256;
    private int serverAsyncSemaphoreValue = 64;
    private int serverChannelMaxIdleTimeSeconds = 120;

    private int serverSocketSndBufSize = NettySystemConfig.socketSndbufSize;
    private int serverSocketRcvBufSize = NettySystemConfig.socketRcvbufSize;
    private boolean serverPooledByteBufAllocatorEnable = true;

start(controller);

        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();

initialize

NamesrvController#initialize

1. 加载配置文件
2. 生成 RemotingServer
3. 启动计划任务十秒扫描不活跃的broker
4. 启动计划任务十秒打印配置文件
5. TLS 模式配置

注册shutdown 函数，监听关闭

start

NamesrvController#start

 public void start() throws Exception {
        this.remotingServer.start();

        if (this.fileWatchService != null) {
            this.fileWatchService.start();
        }
    }