关于nacos:nacos第二章

Nacos 反对服务注册与发现，能够说这个性能时每一个服务治理的根底性能，其余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

这一节次要介绍下这个 NamingExample.java 类，代码如下：

public class NamingExample {public static void main(String[] args) throws NacosException {
        /*
          设置属性，serverAddr：连贯 nacos 的 ip 与 port
          namespace：命名空间如果不设置则默认是 public 设置的话须要在 nacos console 上也创立好，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"));
        /*
         * 这是一个工厂办法，用来创立 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 相同，这个是登记服务实例的
         */
        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());
            }
        });
    }
}

当初一一办法来看一边

NamingFactory 这是一个用来创立服务的动态工厂类，次要提供了两个办法，这两个办法都是通过反射来实例化 NacosNamingService 类，办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);
        }
    }
}

看下下面 NamingFactory 类反射实例化时应用的构造函数

// 这个构造函数其实也是将 serversAddr 地址赋值给 `Properties`，然而灵便扩大就不如第二个，能够赋值更多的属性。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办法，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，下面的几个办法间接或间接调用这个办法的。@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);
    }