nacos第二章

Posted 2021-09-04 少林寺三毛

Nacos 支持服务注册与发现，可以说这个功能时每一个服务治理的基础功能，其他模块都是基于服务注册与发现实现的。

开始实操练习：
在Nacos源码中有个model是example[nacos-example]，这个模块在develop分支中有三个demo类，

App.java、ConfigExample.java、NamingExample.java

这一节主要介绍下这个NamingExample.java类，代码如下：

public class NamingExample {

    public static void main(String[] args) throws NacosException {
        /*
          设置属性，
          serverAddr：连接nacos的ip与port
          namespace：命名空间如果不设置则默认是public 设置的话需要在nacos console上也创建好，否则找不到相应服务的
         */
        Properties properties = new Properties();
        properties.setProperty("serverAddr", System.getProperty("serverAddr"));
        properties.setProperty("namespace", System.getProperty("namespace"));
        /*
         * 这是一个工厂方法，用来创建NamingService的实现类
         */
        NamingService naming = NamingFactory.createNamingService(properties);
        /*
         * 向nacos注册服务 
         */
        naming.registerInstance("nacos.test.3", "11.11.11.11", 8888, "TEST1");

        naming.registerInstance("nacos.test.3", "2.2.2.2", 9999, "DEFAULT");
        /*
         * 获取服务名称为nacos.test.3的所有实例信息
         */
        System.out.println(naming.getAllInstances("nacos.test.3"));
        /*
         * 与 registerInstance 相反，这个是注销服务实例的
         */
        naming.deregisterInstance("nacos.test.3", "2.2.2.2", 9999, "DEFAULT");

        System.out.println(naming.getAllInstances("nacos.test.3"));
        /*
         * 订阅服务
         */
        naming.subscribe("nacos.test.3", new EventListener() {
            @Override
            public void onEvent(Event event) {
                System.out.println(((NamingEvent) event).getServiceName());
                System.out.println(((NamingEvent) event).getInstances());
            }
        });
    }
}

现在逐个方法来看一边

NamingFactory 这是一个用来创建服务的静态工厂类，主要提供了两个方法，这两个方法都是通过反射来实例化NacosNamingService类，方法参数为构造函数的参数。

public class NamingFactory {
    
    /**
     * Create a new naming service.  
     *
     * @param serverList server list
     * @return new naming service
     * @throws NacosException nacos exception
     */
    public static NamingService createNamingService(String serverList) throws NacosException {
        try {
            Class<?> driverImplClass = Class.forName("com.alibaba.nacos.client.naming.NacosNamingService");
            Constructor constructor = driverImplClass.getConstructor(String.class);
            NamingService vendorImpl = (NamingService) constructor.newInstance(serverList);
            return vendorImpl;
        } catch (Throwable e) {
            throw new NacosException(NacosException.CLIENT_INVALID_PARAM, e);
        }
    }
    
    /**
     * Create a new naming service.
     *
     * @param properties naming service properties
     * @return new naming service
     * @throws NacosException nacos exception
     */
    public static NamingService createNamingService(Properties properties) throws NacosException {
        try {
            Class<?> driverImplClass = Class.forName("com.alibaba.nacos.client.naming.NacosNamingService");
            Constructor constructor = driverImplClass.getConstructor(Properties.class);
            NamingService vendorImpl = (NamingService) constructor.newInstance(properties);
            return vendorImpl;
        } catch (Throwable e) {
            throw new NacosException(NacosException.CLIENT_INVALID_PARAM, e);
        }
    }
}

看下上面NamingFactory类反射实例化时使用的构造函数

//这个构造函数其实也是将serversAddr地址赋值给`Properties`，但是灵活扩展就不如第二个，可以赋值更多的属性。
public NacosNamingService(String serverList) throws NacosException {
        Properties properties = new Properties();
        properties.setProperty(PropertyKeyConst.SERVER_ADDR, serverList);
        init(properties);
    }
    
    public NacosNamingService(Properties properties) throws NacosException {
        init(properties);
    }
    
    //这里实例化了N个属性和实例对象
    private void init(Properties properties) throws NacosException {
        ValidatorUtils.checkInitParam(properties);
        this.namespace = InitUtils.initNamespaceForNaming(properties);
        InitUtils.initSerialization();
        initServerAddr(properties);
        InitUtils.initWebRootContext();
        initCacheDir();
        initLogName(properties);
        
        this.eventDispatcher = new EventDispatcher();
        this.serverProxy = new NamingProxy(this.namespace, this.endpoint, this.serverList, properties);
        this.beatReactor = new BeatReactor(this.serverProxy, initClientBeatThreadCount(properties));
        this.hostReactor = new HostReactor(this.eventDispatcher, this.serverProxy, beatReactor, this.cacheDir,
                isLoadCacheAtStart(properties), initPollingThreadCount(properties));
    }

接下来就在看下注册实例的源码。注册实例提供了几种重载方法，以供客户以不同维度注册实例，

@Override
    public void registerInstance(String serviceName, String ip, int port) throws NacosException {
        registerInstance(serviceName, ip, port, Constants.DEFAULT_CLUSTER_NAME);
    }
    
    @Override
    public void registerInstance(String serviceName, String groupName, String ip, int port) throws NacosException {
        registerInstance(serviceName, groupName, ip, port, Constants.DEFAULT_CLUSTER_NAME);
    }
    
    @Override
    public void registerInstance(String serviceName, String ip, int port, String clusterName) throws NacosException {
        registerInstance(serviceName, Constants.DEFAULT_GROUP, ip, port, clusterName);
    }
    
    @Override
    public void registerInstance(String serviceName, String groupName, String ip, int port, String clusterName)
            throws NacosException {
        
        Instance instance = new Instance();
        instance.setIp(ip);
        instance.setPort(port);
        instance.setWeight(1.0);
        instance.setClusterName(clusterName);
        
        registerInstance(serviceName, groupName, instance);
    }
    
    @Override
    public void registerInstance(String serviceName, Instance instance) throws NacosException {
        registerInstance(serviceName, Constants.DEFAULT_GROUP, instance);
    }
    
    //其实最重要的就是这里，上面的几个方法直接或间接调用这个方法的。
    @Override
    public void registerInstance(String serviceName, String groupName, Instance instance) throws NacosException {
        //获取分组的名称
        String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName);
        if (instance.isEphemeral()) {
            BeatInfo beatInfo = beatReactor.buildBeatInfo(groupedServiceName, instance);
            beatReactor.addBeatInfo(groupedServiceName, beatInfo);
        }
        serverProxy.registerService(groupedServiceName, groupName, instance);
    }