深入淺出dubbo源碼系列--provider啓動流程分析

前言

Dubb本身具有很強的擴展性：協議有多種實現，註冊中心和底層通信框架也有多種選擇； 我們下面就梳理下dubbo的核心主流程。主要包括三個子流程：consumer啓動，provider的啓動，接口調用流程。

另外注意：註冊中心我們選擇zookeeper，協議基於dubbo，通信使用netty進行講解。

Provider啓動主流程

整體流程還是比較複雜的，讀源碼的時候我習慣先面後點的方式，可以抓住主要鏈路把流程分析清楚，再扣細節進行點的突破。

核心流程圖，後面就核心流程的一些說明：

1.在系統啓動的時候，根據Spring shemas讀取對應的配置，通過DubboBeanDefinitionParser解析相應的屬性，放入到內存中，給後續服務暴露提供元數據。
DubboNamespaceHandler-init()
registerBeanDefinitionParser(“service”, new DubboBeanDefinitionParser(ServiceBean.class, true));

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:dubbo="http://dubbo.apache.org/schema/dubbo"
       xmlns="http://www.springframework.org/schema/beans"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
       http://dubbo.apache.org/schema/dubbo http://dubbo.apache.org/schema/dubbo/dubbo.xsd">

    <!-- provider's application name, used for tracing dependency relationship -->
    <dubbo:application name="demo-provider"/>

    <!-- use multicast registry center to export service -->
    <dubbo:registry address="zookeeper://localhost:2181" />

    <!-- use dubbo protocol to export service on port 20880 -->
    <dubbo:protocol name="dubbo" port="20880"/>

    <!-- service implementation, as same as regular local bean -->
    <bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/>

    <!-- declare the service interface to be exported -->
    <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/>
</beans>

2.我們看Config模塊中

2.1 ServiceConfig 【export>>doExport>>doExportUrls>>doExportUrlsFor1Protocol】

2.2 獲取代理類，通過動態代理獲取Invoker
proxyFactory.getInvoker
ProxyFactory$Adaptive.getInvoker【注意這個類是DUBBBO SPI動態生成的類】
JavassistProxyFactory.getInvoker(arg0, arg1, arg2)

2.3 進行invoker的發佈[分爲本地和遠程的服務發佈，]
protocol.export(wrapperInvoker)
Protocol$Adaptive.export 【注意這個類是DUBBBO SPI動態生成的類】
2.3.1 進入本地的發佈動作【本地的比較簡單，忽略，只是做了一個 exporterMap.put(key, exporter)】

2.3.2 進入遠程的發佈動作
2.3.2.1 RegistryProtocol.export(final Invoker originInvoker)
2.3.2.1.1 進行DubboProtocol的發佈動作
RegistryProtocol.doLocalExport(originInvoker)
Protocol$Adaptive.export
DubboProtocol.export
2.3.2.1.1.1 將invoker放入exporterMap中，這一步是前面所有步驟的最終結果。非常關鍵的一步
exporterMap.put(key, exporter)key爲 com.alibaba.dubbo.demo.DemoService:20880 value是invoker

2.3.2.1.1.2 打開連接,默認是使用NettyServer
DubboProtocol.openServer(url)
DubboProtocol.createServer(URL url)
Exchangers.bind(url, requestHandler);
HeaderExchanger.bind(URL url, ExchangeHandler handler)
Transporters.bind
NettyServer.doOpen
ServerBootstrap.bind

關鍵類說明

幾個動態生產類【可以拷貝到對應目錄，進行源碼的debug】
ProxyFactory$Adaptive類：

package com.alibaba.dubbo.rpc;

import com.alibaba.dubbo.common.extension.ExtensionLoader;

public class ProxyFactory$Adaptive implements com.alibaba.dubbo.rpc.ProxyFactory {
	public com.alibaba.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1,
			com.alibaba.dubbo.common.URL arg2) throws com.alibaba.dubbo.rpc.RpcException {
		if (arg2 == null)
			throw new IllegalArgumentException("url == null");
		com.alibaba.dubbo.common.URL url = arg2;
		String extName = url.getParameter("proxy", "javassist");
		if (extName == null)
			throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url("
					+ url.toString() + ") use keys([proxy])");
		com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory) ExtensionLoader
				.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
		return extension.getInvoker(arg0, arg1, arg2);
	}

	public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0, boolean arg1)
			throws com.alibaba.dubbo.rpc.RpcException {
		if (arg0 == null)
			throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");
		if (arg0.getUrl() == null)
			throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");
		com.alibaba.dubbo.common.URL url = arg0.getUrl();
		String extName = url.getParameter("proxy", "javassist");
		if (extName == null)
			throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url("
					+ url.toString() + ") use keys([proxy])");
		com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory) ExtensionLoader
				.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
		return extension.getProxy(arg0, arg1);
	}

	public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.RpcException {
		if (arg0 == null)
			throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");
		if (arg0.getUrl() == null)
			throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");
		com.alibaba.dubbo.common.URL url = arg0.getUrl();
		String extName = url.getParameter("proxy", "javassist");
		if (extName == null)
			throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.ProxyFactory) name from url("
					+ url.toString() + ") use keys([proxy])");
		com.alibaba.dubbo.rpc.ProxyFactory extension = (com.alibaba.dubbo.rpc.ProxyFactory) ExtensionLoader
				.getExtensionLoader(com.alibaba.dubbo.rpc.ProxyFactory.class).getExtension(extName);
		return extension.getProxy(arg0);
	}
}

Protocol$Adaptive：

package com.alibaba.dubbo.rpc;

import com.alibaba.dubbo.common.extension.ExtensionLoader;

public class Protocol$Adaptive implements com.alibaba.dubbo.rpc.Protocol {
	public void destroy() {
		throw new UnsupportedOperationException(
				"method public abstract void com.alibaba.dubbo.rpc.Protocol.destroy() of interface com.alibaba.dubbo.rpc.Protocol is not adaptive method!");
	}

	public int getDefaultPort() {
		throw new UnsupportedOperationException(
				"method public abstract int com.alibaba.dubbo.rpc.Protocol.getDefaultPort() of interface com.alibaba.dubbo.rpc.Protocol is not adaptive method!");
	}

	public com.alibaba.dubbo.rpc.Invoker refer(java.lang.Class arg0, com.alibaba.dubbo.common.URL arg1)
			throws com.alibaba.dubbo.rpc.RpcException {
		if (arg1 == null)
			throw new IllegalArgumentException("url == null");
		com.alibaba.dubbo.common.URL url = arg1;
		String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
		if (extName == null)
			throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.Protocol) name from url("
					+ url.toString() + ") use keys([protocol])");
		com.alibaba.dubbo.rpc.Protocol extension = (com.alibaba.dubbo.rpc.Protocol) ExtensionLoader
				.getExtensionLoader(com.alibaba.dubbo.rpc.Protocol.class).getExtension(extName);
		return extension.refer(arg0, arg1);
	}

	public com.alibaba.dubbo.rpc.Exporter export(com.alibaba.dubbo.rpc.Invoker arg0)
			throws com.alibaba.dubbo.rpc.RpcException {
		if (arg0 == null)
			throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument == null");
		if (arg0.getUrl() == null)
			throw new IllegalArgumentException("com.alibaba.dubbo.rpc.Invoker argument getUrl() == null");
		com.alibaba.dubbo.common.URL url = arg0.getUrl();
		String extName = (url.getProtocol() == null ? "dubbo" : url.getProtocol());
		if (extName == null)
			throw new IllegalStateException("Fail to get extension(com.alibaba.dubbo.rpc.Protocol) name from url("
					+ url.toString() + ") use keys([protocol])");
		com.alibaba.dubbo.rpc.Protocol extension = (com.alibaba.dubbo.rpc.Protocol) ExtensionLoader
				.getExtensionLoader(com.alibaba.dubbo.rpc.Protocol.class).getExtension(extName);
		return extension.export(arg0);
	}
}