dubbo源码分析-服务发布

1.dubbo定义的服务，通过spring.handerls对应到DubboNamespaceHandler类

  

        //DubboNamespaceHandler的init()方法进行配置解析注册
        registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
        registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
        registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.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));
        registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
        registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));

2.关注service定义的ServiceBean，实现了多个spring的接口，其中包括ApplicationListener和InitializingBean的接口

      

//举例说明默认的dubbo服务的注册， 先从ServiceBean的export()开始
public void afterPropertiesSet(){
       export();
}
//当有service注册到applicationContext完成时
public void onApplicationEvent(ApplicationEvent event) {
        if (ContextRefreshedEvent.class.getName().equals(event.getClass().getName())) {
        if (isDelay() && ! isExported() && ! isUnexported()) {
                if (logger.isInfoEnabled()) {
                    logger.info("The service ready on spring started. service: " + getInterface());
                }

                export();
            }
        }
    }

3.ProtocolFilterWrapper包装DubboProtocol，调用DubboProtocol.export（）方法进行发布，其中做了两件事情。

   a)用netty建立一个server

   b)起了一个线程定时跑HeaderExchangeServer.startHeatbeatTimer()对所有的客户端连接的chanel进行轮询发送心跳，并计算最后一次发送接受的时间差。

    c)参见HeartBeatTask的run方法

  

public void run() {
        try {
            long now = System.currentTimeMillis();
            for ( Channel channel : channelProvider.getChannels() ) {
                if (channel.isClosed()) {
                    continue;
                }
                try {
                    Long lastRead = ( Long ) channel.getAttribute(
                            HeaderExchangeHandler.KEY_READ_TIMESTAMP );
                    Long lastWrite = ( Long ) channel.getAttribute(
                            HeaderExchangeHandler.KEY_WRITE_TIMESTAMP );
                    if ( ( lastRead != null && now - lastRead > heartbeat )
                            || ( lastWrite != null && now - lastWrite > heartbeat ) ) {
                        Request req = new Request();
                        req.setVersion( "2.0.0" );
                        req.setTwoWay( true );
                        req.setEvent( Request.HEARTBEAT_EVENT );
                        channel.send( req );
                        if ( logger.isDebugEnabled() ) {
                            logger.debug( "Send heartbeat to remote channel " + channel.getRemoteAddress()
                                                  + ", cause: The channel has no data-transmission exceeds a heartbeat period: " + heartbeat + "ms" );
                        }
                    }
                    if ( lastRead != null && now - lastRead > heartbeatTimeout ) {
                        logger.warn( "Close channel " + channel
                                             + ", because heartbeat read idle time out: " + heartbeatTimeout + "ms" );
                        if (channel instanceof Client) {
                        try {
                        ((Client)channel).reconnect();
                        }catch (Exception e) {
//do nothing
}
                        } else {
                        channel.close();
                        }
                    }
                } catch ( Throwable t ) {
                    logger.warn( "Exception when heartbeat to remote channel " + channel.getRemoteAddress(), t );
                }
            }
        } catch ( Throwable t ) {
            logger.warn( "Unhandled exception when heartbeat, cause: " + t.getMessage(), t );
        }
    }

4.其中ProtocolListenerWrapper，提供了相关的监听事件给使用者去用，源码中并没有具体的实现

 public  Exporter export(Invoker invoker) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
            return protocol.export(invoker);
        }
        return new ListenerExporterWrapper(protocol.export(invoker), 
                Collections.unmodifiableList(ExtensionLoader.getExtensionLoader(ExporterListener.class)
                        .getActivateExtension(invoker.getUrl(), Constants.EXPORTER_LISTENER_KEY)));
    }


    public  Invoker refer(Class type, URL url) throws RpcException {
        if (Constants.REGISTRY_PROTOCOL.equals(url.getProtocol())) {
            return protocol.refer(type, url);
        }
        return new ListenerInvokerWrapper(protocol.refer(type, url), 
                Collections.unmodifiableList(
                        ExtensionLoader.getExtensionLoader(InvokerListener.class)
                        .getActivateExtension(url, Constants.INVOKER_LISTENER_KEY)));
    }

5.zookeeper注册的过程主要是ZookeeperRegistry类

  a)客户端建立连接到注册中心

   b)sendEvent线程专门发送和接收消息（举例：比如心跳到zookeeper中心）

   c)eventThread专门处理各种连接事件，并抛给上层的真正的handler线程，由handler线程sendTo相应的队列，这个时候由dubbo实现监听事件并处理