Dubbo源码解析（十） Dubbo Registry以Zookeeper为例

默认是DubboRegistryFactory

@SPI("dubbo") public interface RegistryFactory {      /**      * Connect to the registry      * <p>      * Connecting the registry needs to support the contract: <br>      * 1. When the check=false is set, the connection is not checked, otherwise the exception is thrown when disconnection <br>      * 2. Support username:password authority authentication on URL.<br>      * 3. Support the backup=10.20.153.10 candidate registry cluster address.<br>      * 4. Support file=registry.cache local disk file cache.<br>      * 5. Support the timeout=1000 request timeout setting.<br>      * 6. Support session=60000 session timeout or expiration settings.<br>      *      * @param url Registry address, is not allowed to be empty      * @return Registry reference, never return empty value      */     @Adaptive({"protocol"})     Registry getRegistry(URL url);  }

这个接口很简单，就是服务可以发布到注册中心上面。通过传入的url的protocol来标示。那么具体是在哪里进行调用了这个接口的呢？

在RegistryProtocol进行暴露服务时，这个问题提问已经回答了。看看，这就是提问的艺术。。。

    public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {         // 暴露服务，然后包装暴露者         final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);          // 获取注册中心地址         // 通过服务的registry配置，         //<dubbo:registry id="asRegistry" client="zkclient" protocol="zookeeper" register="true" address="zookeeper:2181" file="D:/dubbo/user/dubbo.registry"/>         //<dubbo:protocol name="dubbo" port="20880" dispatcher="direct" threadpool="fixed" threads="2"/>         //<dubbo:service connections="10" interface="com.wuhulala.dubbo.user.service.UserService" ref="demoService" registry="asRegistry"/>          URL registryUrl = getRegistryUrl(originInvoker);          //根据注册URL 获取注册中心         final Registry registry = getRegistry(originInvoker);          // 处理需要注册到注册中心的地址         final URL registedProviderUrl = getRegistedProviderUrl(originInvoker);          //判断是否需要注册，为什么不放到最上面         boolean register = registedProviderUrl.getParameter("register", true);          ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registedProviderUrl);          if (register) {             // 注册逻辑             register(registryUrl, registedProviderUrl);             ProviderConsumerRegTable.getProviderWrapper(originInvoker).setReg(true);        }        // 省略 ...      }      public void register(URL registryUrl, URL registedProviderUrl) {         // registry在初始化的时候被注入一个自适应的扩展点ExtensionLoader.getExtensionLoader(type).getAdaptiveExtension()         //所以发布的时候也是自适应寻找对应扩展点进行注册到注册中心         Registry registry = registryFactory.getRegistry(registryUrl);         registry.register(registedProviderUrl);     }

下面以Zookeeper为例
AbstractRegistryFactory

   public Registry getRegistry(URL url) {         url = url.setPath(RegistryService.class.getName())                 .addParameter(Constants.INTERFACE_KEY, RegistryService.class.getName())                 .removeParameters(Constants.EXPORT_KEY, Constants.REFER_KEY);         String key = url.toServiceString();         // Lock the registry access process to ensure a single instance of the registry         LOCK.lock();         try {             Registry registry = REGISTRIES.get(key);             if (registry != null) {                 return registry;             }             registry = createRegistry(url);             if (registry == null) {                 throw new IllegalStateException("Can not create registry " + url);             }             REGISTRIES.put(key, registry);             return registry;         } finally {             // Release the lock             LOCK.unlock();         }     }

ZookeeperRegistryFactory

    public Registry createRegistry(URL url) {         return new ZookeeperRegistry(url, zookeeperTransporter);     }

ZookeeperRegistry

   public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {         super(url);         if (url.isAnyHost()) {             throw new IllegalStateException("registry address == null");         }         String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);         if (!group.startsWith(Constants.PATH_SEPARATOR)) {             group = Constants.PATH_SEPARATOR + group;         }         this.root = group;         zkClient = zookeeperTransporter.connect(url);         zkClient.addStateListener(new StateListener() {             public void stateChanged(int state) {                 if (state == RECONNECTED) {                     try {                         recover();                     } catch (Exception e) {                         logger.error(e.getMessage(), e);                     }                 }             }         });     } 

注册节点

    protected void doRegister(URL url) {         try {             // 第二个参数代表是否是临时节点             zkClient.create(toUrlPath(url), url.getParameter(Constants.DYNAMIC_KEY, true));         } catch (Throwable e) {             throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);         }     }

节点目录结构

    private String toUrlPath(URL url) {         // 分类名称/url编码         return toCategoryPath(url) + Constants.PATH_SEPARATOR + URL.encode(url.toFullString());     }

    private String toCategoryPath(URL url) {         return toServicePath(url) + Constants.PATH_SEPARATOR + url.getParameter(Constants.CATEGORY_KEY, Constants.DEFAULT_CATEGORY);     }

    private String toServicePath(URL url) {         String name = url.getServiceInterface();         if (Constants.ANY_VALUE.equals(name)) {             return toRootPath();         }         return toRootDir() + URL.encode(name);     }

    private String toRootDir() {         if (root.equals(Constants.PATH_SEPARATOR)) {             return root;         }         return root + Constants.PATH_SEPARATOR;     }

        String group = url.getParameter(Constants.GROUP_KEY, DEFAULT_ROOT);         if (!group.startsWith(Constants.PATH_SEPARATOR)) {             group = Constants.PATH_SEPARATOR + group;         }         this.root = group;

所以节点的注册信息就是 group{默认dubbo}/serviceName/category{默认providers}/url编码

总体来说 registry这里不是特别的复杂

文章来源: Dubbo源码解析（十） Dubbo Registry以Zookeeper为例