2、Dubbo源码解析--服务发布原理（Netty服务暴露）
一、服务发布 - 原理：
首先看Dubbo日志，截取重要部分：
1）暴露本地服务
Export dubbo service com.alibaba.dubbo.demo.DemoService to local registry, dubbo version: 2.0.0, current host: 10.165.2.47
2）暴露远程服务
Export dubbo service com.alibaba.dubbo.demo.DemoService to url dubbo://10.165.2.47:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=10.165.2.47&bind.port=20880&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=3880&qos.port=22222&side=provider×tamp=1520303067433, dubbo version: 2.0.0, current host: 10.165.2.47 Register dubbo service com.alibaba.dubbo.demo.DemoService url dubbo://10.165.2.47:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=10.165.2.47&bind.port=20880&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=3880&qos.port=22222&side=provider×tamp=1520303067433 to registry registry://224.5.6.7:1234/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&pid=3880&qos.port=22222®istry=multicast×tamp=1520303067418, dubbo version: 2.0.0, current host: 10.165.2.47
3）启动Netty
Start NettyServer bind /0.0.0.0:20880, export /10.165.2.47:20880, dubbo version: 2.0.0, current host: 10.165.2.47
4）打开Zookeeper
INFO zookeeper.ClientCnxn: Opening socket connection to server /192.168.48.117:2181
5）注册到Zookeeper
Register: dubbo://10.165.2.47:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=3880&side=provider×tamp=1520303067433, dubbo version: 2.0.0, current host: 10.165.2.47
6）监听Zookeeper
Subscribe: provider://10.165.2.47:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=3880&side=provider×tamp=1520303067433, dubbo version: 2.0.0, current host: 10.165.2.47
7）频繁发送广播包，注册中心利用广播包监听provider健康状况
[DUBBO] Send broadcast message: subscribe provider://10.165.2.47:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=3880&side=provider×tamp=1520303067433 to /224.5.6.7:1234, dubbo version: 2.0.0, current host: 10.165.2.47 [DUBBO] Receive multicast message: subscribe provider://10.165.2.47:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&category=configurators&check=false&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello&pid=3880&side=provider×tamp=1520303067433 from /10.165.2.47:1234, dubbo version: 2.0.0, current host: 10.165.2.47
二、根据原理分析源码
1）首先看Provider注册文件：
<bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/> <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/>
可以看到，是通过dubbo的schema service进行注入的，那我们找到DubboNameSpaceHandler，Dubbo命名空间处理器，找到<dubbo:service>标签解析行：
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("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)); //这里就是<dubbo:service>标签的解析注入入口 registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false)); registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser()); }
2）上面new DubboBeanDefinitionParser是<dubbo:service>解析注入入口，那ServiceBean.class就是<dubbo:service>标签的发布订阅入口，进入ServiceBean可以看到一个核心方法onApplicationEvent()，其中export()就是发布方法:
public void onApplicationEvent(ContextRefreshedEvent event) { if (isDelay() && !isExported() && !isUnexported()) { if (logger.isInfoEnabled()) { logger.info("The service ready on spring started. service: " + getInterface()); } //这里是发布方法 export(); } }
3）发布代码处理路径
ServiceBean.onApplicationEvent
-->export()
-->ServiceConfig.export()
-->doExport()
-->doExportUrls() //里面有个for循环，代表一个服务可以有多个通信协议，例如tcp、http、dubbo等协议，默认是tcp协议
-->loadRegistries(true) //加载注册信息，组装注册中心url信息，如源码中config.properties中读取dubbo.registry.address = zookeeper://192.168.99.100:32770链接信息，组装Provider注册链接串
-->doExportUrlsFor1Protocol(protocolConfig, registryURLs)
// export to local if the config is not remote (export to remote only when config is remote)远程暴露
-->exportLocal(url)
-->proxyFactory.getInvoker(ref, (Class) interfaceClass, local))
-->ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension("javassist");
-->extension.getInvoker(arg0, arg1, arg2)
-->StubProxyFactoryWrapper.getInvoker(T proxy, Class<T> type, URL url)
-->proxyFactory.getInvoker(proxy, type, url)
-->JavassistProxyFactory.getInvoker(T proxy, Class<T> type, URL url)
-->Wrapper.getWrapper(com.alibaba.dubbo.demo.provider.DemoServiceImpl)
-->makeWrapper(Class<?> c)
-->return new AbstractProxyInvoker<T>(proxy, type, url)
-->protocal.export //本地暴露
-->Protocal$Adaptive.export
-->ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocal.class).getExtension("injvm");
-->extension.export(arg0)
-->ProtocalFilterWrapper.export
-->buildInvokerChain //创建8个Filter
-->ProtocalListenerWrapper.export
-->InjvmProtocal.export
-->return new InjvmExporter
-->InjvmExporter(Invoker<T> invoker, String key, Map<String, Exporter<?>> exporterMap) {super(invoker);
this.key = key;
this.exporterMap = exporterMap;
exporterMap.put(key, this); //key=com.alibaba.dubbo.demo.DemoService this=InjvmExporter
}
// export to local if the config is not remote (export to remote only when config is remote)远程暴露
-->proxyFactory.getInvoker()原理和本地暴露一样都是为了获取一个Invoker对象
-->protocal.export
-->Protocal$Adaptive.ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocal.class).getExtension("register");
-->extension.export(arg0)
-->ProtocalFilterWrappter.export
-->ProtocalListenerWrapper.export
-->RegistryProtocal.export
-->doLocalExport(originInvoker)
-->getCacheKey(originInvoker) //读取dubbo://192.168.100.51:20880/
-->protocal.export
-->Protocol$Adaptive.export
-->ExtensionLoader.getExtensionLoader(com.alibaba.dubbo.rpc.Protocl.class).getExtension("dubbo");
-->extension.export(arg0)
-->ProtocolFilterWrapper.export
-->buildInvokerChain//创建8个Filter
-->ProtocalListenerWrapper.export
-------1、netty服务暴露的开始-------- -->DubboProtocal.export
-->serviceKey(url) //组装key=com.alibaba.dubbo.demo.DemoService:20880
-->目的：exporterMap.put(key, this); //key=com.alibaba.dubbo.demo.DemoService:20880 this=
-->openServer(url)
-->createServer(url)
--------2、信息交换层exchange 开始-------- -->Exchanges.bind(url, requestHandler) //exchanger是一个信息交换层
-->getExchanger(url)
-->getExchange(type)
-->ExtensionLoader.getExtensionLoader(Exchanger.class).getExtension("header")
-->HeaderExchanger.bind
-->Transporters.bind(url, new DecoderHandler(new HeaderExchangeHandler(handler)))
-->new HeaderExchangeHandler(handler) //this.handler = handler
-->new DecoderHandler
-->new AbstractChannelHandlerDelegate //this.handler = handler;
------------>3、网络传输层 transporter ------------ -->Transporters.bind
-->getTransporter
-->ExtensionLoader.getExtensionLoader(Transporter.class).getAdaptiveExtension();
-->Transporter$Adaptive.bind
//netty服务暴露
-->ExtensionLoader.getExtensionLoader(com.alibaba.remoting.Transporter.class).getExtension("netty")
-->extension.bind(arg0, arg1)
-->NettyTransporter.bind
-->new NettyServer(url, listener)
-->AbstractPeer //this.url = url; this.handler = handler;
-->AbstractEndpoint //codec timeout=1000 connectTimeout=3000
-->AbstractServer //bindAddress accepts=0 idleTimeout=600000
----------->4、打开端口，暴露netty服务 -------------- -->doOpen()
-->设置NioServerSocketChannelFactory boss worker的线程池 线程个数为3
-->设置编码handler
-->bootstrap.bind(getBindAddress())
-->new HeaderExchangeServer()
-->this.server = NettyServer
-->this.heartbeat=600000
-->heartbeatTimeout=180000
-->startHeatbeatTimer() //这是一个心跳定时器，采用线程池ScheduledExecutePool，如果断开了就心跳重连
-->
说说上述这些类及方法的概念作用：”
1、proxyFactory:就是为了获取一个接口的代理类，例如获取一个远程接口的代理。
它有2个方法，代表2个作用
a、getInvoker:针对server端，将服务对象，例如DemoServiceImpl包装成一个Wrapper对象。
b、getProxy：针对client端，创建接口的代理对象，例如DemoService的接口。
2、makeWrapper：它类似spring的BeanWrapper，它就是包装了一个接口或一个类，可以通过Wrapper对实例对象进行赋值取值以及指定方法的调用。
3、Invoker：它是一个可执行的对象，能够根据方法名称、参数得到相应的执行结果。
它里面有一个很重要的方法Result invoke(Invocation invocation)，Invocation是包含了需要执行的方法和参数的重要信息，目前它只有2个实现类RpcInvocation MockInvocation
它有3种类型的Invoker
1、本地执行类的Invoker
2、远程通信类的Invoker
3、多个远程通信执行类的Invoker聚合成集群版的Invoker
4、Protocol：
1）export暴露远程服务（用语服务端），就是将proxyFactory.getInvoker创建的代理类invoker对象，通过协议暴露给外部。
2）refer：引用远程服务（用于客户端）
5、Exporter：维护invoker的生命周期
6、exchanger：信息交换层，封装请求响应模式同步转异步
7、transporter：网络传输层，用来抽象Netty（dubbo默认）或者Mina的统一接口
4）暴露本地服务与暴露远程服务的区别是什么？
a、暴露本地服务：指暴露在同一个JVM里面，不用通过zk来进行远程通信，例如在同一个服务里面（tomcat），自己调用自己的接口，就无需进行网络IP连接通信。
b、暴露远程服务：指暴露给远程客户端的IP和端口号，通过网络来实现通信。
