dubbo核心之消费端的Invoker（五）

一、消费端Invoker

1. 还是在Spring的扩展点进入（注解版从ReferenceAnnotationBeanPostProcessor）

   1. DubboNamespaceHandler
   @Override
   public void init() {
       registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
       registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
       registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
       registerBeanDefinitionParser("config-center", new DubboBeanDefinitionParser(ConfigCenterBean.class, true));
       registerBeanDefinitionParser("metadata-report", new DubboBeanDefinitionParser(MetadataReportConfig.class, true));
       registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
       registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
       registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
       registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
       registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
       //2.
       registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
       registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser());
   }
   

   2. ReferenceBean实现FactoryBean，Spring中规定FactoryBean实现类实例化的是getObject()方法返回的对象
   
   public class ReferenceBean<T> extends ReferenceConfig<T> implements FactoryBean, ApplicationContextAware, InitializingBean, DisposableBean {
   	//省略代码。。。
       @Override
       public Object getObject() {
       	//3.
           return get();
       }
   
   }
   
   

   3. ReferenceConfig
   public synchronized T get() {
   	//检查和更新配置
       checkAndUpdateSubConfigs();
   
       if (destroyed) {
           throw new IllegalStateException("The invoker of ReferenceConfig(" + url + ") has already destroyed!");
       }
       if (ref == null) {
       	//4.
           init();
       }
       return ref;
   }
   

   4.
   private void init() {
       //省略代码。。。构建一个map
   
   	//创建一个代理类
   	//5.
       ref = createProxy(map);
   
   }
   
   

   5. 
   private T createProxy(Map<String, String> map) {
       //是否在jvm中
       if (shouldJvmRefer(map)) {
           URL url = new URL(LOCAL_PROTOCOL, LOCALHOST_VALUE, 0, interfaceClass.getName()).addParameters(map);
           invoker = REF_PROTOCOL.refer(interfaceClass, url);
           if (logger.isInfoEnabled()) {
               logger.info("Using injvm service " + interfaceClass.getName());
           }
       } else {
           urls.clear(); // reference retry init will add url to urls, lead to OOM
   
           //点对点，按用户配置直连？ 或者按照配置中心的连接
           if (url != null && url.length() > 0) { // user specified URL, could be peer-to-peer address, or register center's address.
               String[] us = SEMICOLON_SPLIT_PATTERN.split(url);
               if (us != null && us.length > 0) {
                   for (String u : us) {
                       URL url = URL.valueOf(u);
                       if (StringUtils.isEmpty(url.getPath())) {
                           url = url.setPath(interfaceName);
                       }
                       // 检测 url 协议是否为 registry，若是，表明用户想使用指定的注册中心
                       if (REGISTRY_PROTOCOL.equals(url.getProtocol())) {
                       	// 将 map 转换为查询字符串，并作为 refer 参数的值添加到url 中
                           urls.add(url.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
                       } else {
                       	// 合并 url，移除服务提供者的一些配置（这些配置来源于用户配置的 url 属性），
   						// 比如线程池相关配置。并保留服务提供者的部分配置，比如版本， group，时间戳等
   						// 最后将合并后的配置设置为 url 查询字符串中
                           urls.add(ClusterUtils.mergeUrl(url, map));
                       }
                   }
               }
           //没有配置url，从注册中心去获得服务地址
           } else {
               // if protocols not injvm checkRegistry
               if (!LOCAL_PROTOCOL.equalsIgnoreCase(getProtocol())){
                   checkRegistry();
                   //URL是 registry://
                   List<URL> us = loadRegistries(false);
                   if (CollectionUtils.isNotEmpty(us)) {
                       for (URL u : us) {
                           URL monitorUrl = loadMonitor(u);
                           if (monitorUrl != null) {
                               map.put(MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
                           }
                           urls.add(u.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
                       }
                   }
                   if (urls.isEmpty()) {
                       throw new IllegalStateException("No such any registry to reference " + interfaceName + " on the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", please config  to your spring config.");
                   }
               }
           }
           //一个服务提供者
           if (urls.size() == 1) {
               //构建一个invoker(Protocol)
               //Protocol$Adaptive， url是registry， 
               //再加上包装类，所以new QosProtocolWrapper(new ProtocolListenerWrapper(new ProtocolFilterWrapper(new RegisterProtol())))
               //最终是RegisterProtocol.refer()
               //6.
               invoker = REF_PROTOCOL.refer(interfaceClass, urls.get(0));
           //多个服务提供者，构建集群
           } else {
               List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
               URL registryURL = null;
               for (URL url : urls) {
                   invokers.add(REF_PROTOCOL.refer(interfaceClass, url));
                   if (REGISTRY_PROTOCOL.equals(url.getProtocol())) {
                       registryURL = url; // use last registry url
                   }
               }
               if (registryURL != null) { // registry url is available
                   // use RegistryAwareCluster only when register's CLUSTER is available
                   URL u = registryURL.addParameter(CLUSTER_KEY, RegistryAwareCluster.NAME);
                   // The invoker wrap relation would be: RegistryAwareClusterInvoker(StaticDirectory) -> FailoverClusterInvoker(RegistryDirectory, will execute route) -> Invoker
                   invoker = CLUSTER.join(new StaticDirectory(u, invokers));
               } else { // not a registry url, must be direct invoke.
                   invoker = CLUSTER.join(new StaticDirectory(invokers));
               }
           }
       }
   
       if (shouldCheck() && !invoker.isAvailable()) {
           throw new IllegalStateException("Failed to check the status of the service " + interfaceName + ". No provider available for the service " + (group == null ? "" : group + "/") + interfaceName + (version == null ? "" : ":" + version) + " from the url " + invoker.getUrl() + " to the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion());
       }
       if (logger.isInfoEnabled()) {
           logger.info("Refer dubbo service " + interfaceClass.getName() + " from url " + invoker.getUrl());
       }
       /**
        * @since 2.7.0
        * ServiceData Store
        */
       MetadataReportService metadataReportService = null;
       if ((metadataReportService = getMetadataReportService()) != null) {
           URL consumerURL = new URL(CONSUMER_PROTOCOL, map.remove(REGISTER_IP_KEY), 0, map.get(INTERFACE_KEY), map);
           metadataReportService.publishConsumer(consumerURL);
       }
       // create service proxy
       //8.
       return (T) PROXY_FACTORY.getProxy(invoker);
   }
   

   6. RegistryProtocol
   @Override
   @SuppressWarnings("unchecked")
   public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
       //根据配置获取注册中心地址  zookeeper://
       url = URLBuilder.from(url)
               .setProtocol(url.getParameter(REGISTRY_KEY, DEFAULT_REGISTRY))
               .removeParameter(REGISTRY_KEY)
               .build();
       //ZookeeperRegistery
       Registry registry = registryFactory.getRegistry(url);
       //接口是不是RegistryService类型，register://
       if (RegistryService.class.equals(type)) {
           return proxyFactory.getInvoker((T) registry, type, url);
       }
   
       //解析group，根据group获取cluster类型  group="a,b" or group="*"
       Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(REFER_KEY));
       String group = qs.get(GROUP_KEY);
       if (group != null && group.length() > 0) {
           if ((COMMA_SPLIT_PATTERN.split(group)).length > 1 || "*".equals(group)) {
               return doRefer(getMergeableCluster(), registry, type, url);
           }
       }
       //7.
       return doRefer(cluster, registry, type, url);
   }
   
   

   7.  无非就是zk上获取服务地址，netty连接过去，订阅zk上服务节点的变化
   private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
   
       //创建一个RegistryDirectory
       RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
       directory.setRegistry(registry); //registry -> 连接zk的api   ->获得url地址
       directory.setProtocol(protocol); //protocol -> DubboProtocol()  -> 建立通信
       // all attributes of REFER_KEY
       Map<String, String> parameters = new HashMap<String, String>(directory.getUrl().getParameters());
       //consumer 地址
       URL subscribeUrl = new URL(CONSUMER_PROTOCOL, parameters.remove(REGISTER_IP_KEY), 0, type.getName(), parameters);
       if (!ANY_VALUE.equals(url.getServiceInterface()) && url.getParameter(REGISTER_KEY, true)) {
           directory.setRegisteredConsumerUrl(getRegisteredConsumerUrl(subscribeUrl, url));
           registry.register(directory.getRegisteredConsumerUrl()); //consumer://
       }
       directory.buildRouterChain(subscribeUrl);
       //订阅zk上节点的变化
       //9.
       directory.subscribe(subscribeUrl.addParameter(CATEGORY_KEY,
               PROVIDERS_CATEGORY + "," + CONFIGURATORS_CATEGORY + "," + ROUTERS_CATEGORY));
       /******************************************/
   
   
       //new MockClusterWrapper(new FailoverCluster())
       Invoker invoker = cluster.join(directory);
       ProviderConsumerRegTable.registerConsumer(invoker, url, subscribeUrl, directory);
       return invoker;
   }
   
   

   8. PROXY_FACTORY 是new StubProxyFactoryWrapper(new JavassistProxyFactory())
   返回一个代理类，最终会执行InvokerInvocationHandler的invoke方法。
   public <T> T getProxy(Invoker<T> invoker, Class<?>[] interfaces) {
       return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker));
   }
   
   

   9. 主要看下订阅节点的步骤
      RegistryDirectory对象把zk的节点抽象成目录并发布一个订阅
      
    public void subscribe(URL url) {
       setConsumerUrl(url);
       CONSUMER_CONFIGURATION_LISTENER.addNotifyListener(this);
       serviceConfigurationListener = new ReferenceConfigurationListener(this, url);
       //registry = ZookeeperRegistry， this = RegistryDirectory
       //10.
       registry.subscribe(url, this);
   }
    
   

   10. FailBackRegistry
   @Override
   public void subscribe(URL url, NotifyListener listener) {
       super.subscribe(url, listener);
       removeFailedSubscribed(url, listener);
       try {
           //订阅
           //11.
           doSubscribe(url, listener);
       } catch (Exception e) {
           Throwable t = e;
   
           List<URL> urls = getCacheUrls(url);
           if (CollectionUtils.isNotEmpty(urls)) {
               notify(url, listener, urls);
               logger.error("Failed to subscribe " + url + ", Using cached list: " + urls + " from cache file: " + getUrl().getParameter(FILE_KEY, System.getProperty("user.home") + "/dubbo-registry-" + url.getHost() + ".cache") + ", cause: " + t.getMessage(), t);
           } else {
               // If the startup detection is opened, the Exception is thrown directly.
               boolean check = getUrl().getParameter(Constants.CHECK_KEY, true)
                       && url.getParameter(Constants.CHECK_KEY, true);
               boolean skipFailback = t instanceof SkipFailbackWrapperException;
               if (check || skipFailback) {
                   if (skipFailback) {
                       t = t.getCause();
                   }
                   throw new IllegalStateException("Failed to subscribe " + url + ", cause: " + t.getMessage(), t);
               } else {
                   logger.error("Failed to subscribe " + url + ", waiting for retry, cause: " + t.getMessage(), t);
               }
           }
   
           //失败后续重试
           addFailedSubscribed(url, listener);
       }
   }
   

   11.ZookeeperRegistry
   @Override
   public void doSubscribe(final URL url, final NotifyListener listener) {
       //省略代码。。。
       
       List<URL> urls = new ArrayList<>();
       for (String path : toCategoriesPath(url)) {
       	//缓存操作
           ConcurrentMap<NotifyListener, ChildListener> listeners = zkListeners.get(url);
           if (listeners == null) {
               zkListeners.putIfAbsent(url, new ConcurrentHashMap<>());
               listeners = zkListeners.get(url);
           }
           ChildListener zkListener = listeners.get(listener);
           if (zkListener == null) {
           	//这里比较重要， 构建一个ChildListener 的匿名内部类 ,在节点变化时候
           	//在他的childChanged()方法执行ZookeeperRegistry.this.notify()方法  重新构建Invoke
               listeners.putIfAbsent(listener, (parentPath, currentChilds) -> ZookeeperRegistry.this.notify(url, listener, toUrlsWithEmpty(url, parentPath, currentChilds)));
               zkListener = listeners.get(listener);
           }
           zkClient.create(path, false);
           //zk上Configuration；consumer ；router ；provider 的子节点
           List<String> children = zkClient.addChildListener(path, zkListener);
           if (children != null) {
               urls.addAll(toUrlsWithEmpty(url, path, children));
           }
       }
       //第一次启动时候构建invoke， Map
       //并建立连接
       //12.
       notify(url, listener, urls);
     
   }
   

   12.FailBackRegistry
   @Override
   protected void notify(URL url, NotifyListener listener, List<URL> urls) {
       if (url == null) {
           throw new IllegalArgumentException("notify url == null");
       }
       if (listener == null) {
           throw new IllegalArgumentException("notify listener == null");
       }
       try {
       	//异步通知
       	//13.
           doNotify(url, listener, urls);
       } catch (Exception t) {
           // Record a failed registration request to a failed list, retry regularly
           addFailedNotified(url, listener, urls);
           logger.error("Failed to notify for subscribe " + url + ", waiting for retry, cause: " + t.getMessage(), t);
       }
   }
   

   13.一步步找到 RegistryDirectory
   private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
     		//代码省略
     		//protocol = 各种wrapper后的DubboProtocol
     		//14.
          invoker = new InvokerDelegate<>(protocol.refer(serviceType, url), url, providerUrl);
                 
   }
   

   14.DubboProtocol
   @Override
   public <T> Invoker<T> refer(Class<T> serviceType, URL url) throws RpcException {
       optimizeSerialization(url);
   
       // create rpc invoker.
       //getClients(url)建立连接
       //15.
       DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);
       invokers.add(invoker);
   
       return invoker;
   }
   

   15.
   private ExchangeClient[] getClients(URL url) {
       // whether to share connection
   
       boolean useShareConnect = false;
   
       int connections = url.getParameter(Constants.CONNECTIONS_KEY, 0);
       List<ReferenceCountExchangeClient> shareClients = null;
       // if not configured, connection is shared, otherwise, one connection for one service
       if (connections == 0) {
           useShareConnect = true;
   
           /**
            * The xml configuration should have a higher priority than properties.
            */
           String shareConnectionsStr = url.getParameter(Constants.SHARE_CONNECTIONS_KEY, (String) null);
           connections = Integer.parseInt(StringUtils.isBlank(shareConnectionsStr) ? ConfigUtils.getProperty(Constants.SHARE_CONNECTIONS_KEY,
                   Constants.DEFAULT_SHARE_CONNECTIONS) : shareConnectionsStr);
            //默认共享连接，同一个连接通信
            //16.
           shareClients = getSharedClient(url, connections);
       }
   
       ExchangeClient[] clients = new ExchangeClient[connections];
       for (int i = 0; i < clients.length; i++) {
           if (useShareConnect) {
               clients[i] = shareClients.get(i);
   
           } else {
               clients[i] = initClient(url);
           }
       }
   
       return clients;
   }
   

   16.
   private List<ReferenceCountExchangeClient> getSharedClient(URL url, int connectNum) {
       String key = url.getAddress();
       List<ReferenceCountExchangeClient> clients = referenceClientMap.get(key);
   
       if (checkClientCanUse(clients)) {
           batchClientRefIncr(clients);
           return clients;
       }
   	//并发检查
       locks.putIfAbsent(key, new Object());
       synchronized (locks.get(key)) {
           clients = referenceClientMap.get(key);
           // dubbo check
           if (checkClientCanUse(clients)) {
               batchClientRefIncr(clients);
               return clients;
           }
   
           // connectNum must be greater than or equal to 1
           connectNum = Math.max(connectNum, 1);
   
           // If the clients is empty, then the first initialization is
           //第一次初始化
           if (CollectionUtils.isEmpty(clients)) {
           	//17.
               clients = buildReferenceCountExchangeClientList(url, connectNum);
               referenceClientMap.put(key, clients);
   
           } else {
               for (int i = 0; i < clients.size(); i++) {
                   ReferenceCountExchangeClient referenceCountExchangeClient = clients.get(i);
                   // If there is a client in the list that is no longer available, create a new one to replace him.
                   if (referenceCountExchangeClient == null || referenceCountExchangeClient.isClosed()) {
                       clients.set(i, buildReferenceCountExchangeClient(url));
                       continue;
                   }
   
                   referenceCountExchangeClient.incrementAndGetCount();
               }
           }
   
           /**
            * I understand that the purpose of the remove operation here is to avoid the expired url key
            * always occupying this memory space.
            */
           locks.remove(key);
   
           return clients;
       }
   }
   

   17.
   private ReferenceCountExchangeClient buildReferenceCountExchangeClient(URL url) {
   	//构建连接
       ExchangeClient exchangeClient = initClient(url);
   
       return new ReferenceCountExchangeClient(exchangeClient);
   }