dubbo工作原理

2022-10-24 07:51:37

part -- 外挂
1.dubbo借助spring的schema启动和初始化
1.1 spring扫描所有jar下META-INF的spring.handlers和spring.schemas。
1.2 运行spring.handlers下定义的DubboNamespaceHandler的init方法。
1.3 spring加载xml，执行DubboBeanDefinitionParser的parse方法，通过RootBeanDefinition将serviceBean暴露给spring。（实际调用AutowireCapableBeanFactory.registerBeanDefinition）
1.4 serviceBean实现了BeanNameAware接口，自动注入spring中的单例name。

part -- 服务暴露（生产者）
2.dubbo服务暴露
2.1 serviceBean实现了ApplicationListener，在bean初始化时触发onApplicationEvent方法，调用serviceConfig的export方法。
2.2 serviceConfig初始化，先初始化静态变量protocol和proxyFactory。
getExtensionLoader.getExtensionLoader ->getAdaptiveExtension->createAdaptiveExtension->getAdaptiveExtensionClass->getExtensionClasses->loadExtensionClasses
->loadFile->createAdaptiveExtensionClassCode
loadFile采用的是java spi的思想，分别读取META-INF/services/，META-INF/dubbo/，META-INF/dubbo/internal/下文件进行解析。
以protocol为例，其中ProtocolFilterWrapper和ProtocolListenerWrapper是有参数为protocol构造函数的，被放到Set<Class<?>> cachedWrapperClasses（后面会用到）中。
没有protocol构造函数，但是有@Adaptive注解的，被放到Holder<Object> cachedAdaptiveInstance中。
以上都不满足的放到cachedClasses中。
createAdaptiveExtensionClassCode通过javassist字节码技术生成代理类Protocol$Adpative，ProxyFactory$Adpative。
附上两个动态类的源码。可以看到protocol默认的是dubbo，proxy默认的是javassist。
2.3 export判断是否需要延迟暴露，执行暴露方法doExport()。
2.4 doExport检查通过，调用doExportUrls
2.5 doExportUrls根据不同的协议将服务以URL（dubbo）形式暴露。
2.6 如果服务未配置成remote,则本地暴露（exportLocal），如果未配置成local，则注册服务（registryProtocol）
2.7 exportLocal：生成本地protocol（Constants.LOCAL_PROTOCOL = injvm），
proxyFactory.getInvoker StubProxyFactoryWrapper->JavassistProxyFactory.getInvoker。Wrapper.getWrappery获取服务的封装代理类（javassist动态字节码）,详细参照ClassGenerator.toClass。
protocol.export ExtensionLoader.getExtension(injvm)->createExtension -> getExtensionClasses(返回cachedClasses对应的值)
接着循环cachedWrapperClasses,层层装饰（装饰模式）,InjvmProtocol,ProtocolFilterWrapper，ProtocolListenerWrapper增强服务。
ProtocolFilterWrapper buildInvokerChain建立了filter链，方便开发者根据业务进行扩展。
registryProtocol export ->ProtocolFilterWrapper export-> ProtocolListenerWrapper export->dubboProtocol export。

3.netty启动
3.1 openServer netty server打开侦听服务，并缓存服务。
dubbo -> export() -> openServer() -> createServer() -> Exchangers.bind()(HeaderExchanger) -> NettyTransporter -> NettyServer.open()(编码解码采用exchange)
netty ChannelFactory(boss worker) ChannelPipeline(责任链模式) ChannelHandler(处理器) --- 反应器模式

part -- 服务引用(消费者)
4.dubbo服务引用
4.1 referenceBean实现了InitializingBean接口，在afterPropertiesSet后执行getObject()方法，调用referenceConfig的init方法。
4.2 StaticContext.getSystemContext()是dubbo全局的线程安全上下文，存放方法调用的相关信息。
4.2 createProxy，设置invoker，这里的invoker有协议默认的dubbo invoker，cluster invoker（重连机制，默认Failover，重试两次，一共三次）
返回InvokerInvocationHandler(javassist动态字节码改造后的代理，执行方法时，实际执行的是invoker的doinvoke方法)
cluster invoker的doinvoke方法会调用select()，负载均衡，默认RandomLoadBalance
4.3 获取dubbo invoker时，调用dubbo的refer，调用getClients获取ExchangeClient，默认的ExchangeClient是共享的getSharedClient。initClient默认是非延迟的，调用Exchangers.connect，最终调用HeaderExchanger.connect,调用
Transporters.connect，同生产者一样，默认的Transporters是netty。因此最终的ExchangeClient是NettyClient。
4.3 dubbo invoker doinvoke方法，ExchangeClient.request方法，结果通过future的get方法返回，get方法通过lock+while+超时控制。
4.4 ExchageClient.request最终调用的是nettyChannel
1.NettyHandler.messageReceived(ChannelHandlerContext ctx, MessageEvent e)
2.AbstractPeer.received(Channel ch, Object msg)
3.MultiMessageHandler.received(Channel channel, Object message)
4.AllChannelHandler.received(Channel channel, Object message)
5.DecodeHandler.received(Channel channel, Object message)
6.HeaderExchangeHandler.received(Channel channel, Object message)
7.DefaultFuture.received(Channel channel, Response response) //注意是static方法
DefaultFuture future = FUTURES.remove(response.getId());
if (future != null) {
future.doReceived(response);
}

http://blog.csdn.net/a19881029/article/details/51058428

spring
1. 入口ContextLoaderListener监听器，调用contextInitialized方法，ContextLoder的initWebApplicationContext，createWebApplicationContext默认创建ContextLoader.properties里的XmlWebApplicationContext,强制转换成configureAndRefreshWebApplicationContext
最终调用AbstractApplicationContext的refresh方法（前面调用了ApplicationContextInitializer的initialize，这里可以做一些spring默认规则的修改，比如id重复bean处理，spring默认覆盖）
2.

 动态生成的Protocol$Adpative.class

package com.alibaba.dubbo.rpc;

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

public class Protocol$Adpative 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 java.lang.Class {

        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.Invoker {

        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);

    }

}

动态生成的ProxyFactory$Adpative.class

package com.alibaba.dubbo.rpc;

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

public class ProxyFactory$Adpative implements com.alibaba.dubbo.rpc.ProxyFactory {

    public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.Invoker {

        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);

    }

    public com.alibaba.dubbo.rpc.Invoker getInvoker(java.lang.Object arg0, java.lang.Class arg1,

            com.alibaba.dubbo.common.URL arg2) throws java.lang.Object {

        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);

    }

}

{class com.alibaba.dubbo.config.spring.extension.SpringExtensionFactory=com.alibaba.dubbo.config.spring.extension.SpringExtensionFactory@5d1275be, class com.alibaba.dubbo.common.compiler.support.JavassistCompiler=com.alibaba.dubbo.common.compiler.support.JavassistCompiler@66f03cae, class com.alibaba.dubbo.common.extension.factory.SpiExtensionFactory=com.alibaba.dubbo.common.extension.factory.SpiExtensionFactory@261ff84e}

injvm://127.0.0.1/com.ihome.tf.order.service.IBenefitFoundService?anyhost=true&application=tf-order&default.retries=0&default.timeout=10000&dubbo=2.5.3&interface=com.ihome.tf.order.service.IBenefitFoundService&methods=update,clear,qryBenefitFndOrderList,qryCheckPassedBenefitList,qryBenefitFoundOrderSumInf,verify,qryBenefitFound&owner=tf&pid=1492&revision=0.0.1-SNAPSHOT&side=provider&timestamp=1457518110700

动态生成的Wrapper1.class

package com.alibaba.dubbo.common.bytecode;

import com.prepay.dto.ShareRulesReq;

import com.prepay.service.IOutShareService;

import java.lang.reflect.InvocationTargetException;

import java.util.Map;

public class Wrapper1 extends Wrapper

  implements ClassGenerator.DC

{

  public static String[] pns;

  public static Map pts;

  public static String[] mns;

  public static String[] dmns;

  public static Class[] mts0;

  public static Class[] mts1;

  public static Class[] mts2;

  public String[] getPropertyNames()

  {

    return pns;

  }

  public boolean hasProperty(String paramString)

  {

    return jdField_pts_of_type_JavaUtilMap.containsKey(paramString);

  }

  public Class getPropertyType(String paramString)

  {

    return (Class)jdField_pts_of_type_JavaUtilMap.get(paramString);

  }

  public String[] getMethodNames()

  {

    return mns;

  }

  public String[] getDeclaredMethodNames()

  {

    return dmns;

  }

  public void setPropertyValue(Object paramObject1, String paramString, Object paramObject2)

  {

    try

    {

      IOutShareService localIOutShareService = (IOutShareService)paramObject1;

    }

    catch (Throwable localThrowable)

    {

      throw new IllegalArgumentException(localThrowable);

    }

    throw new NoSuchPropertyException("Not found property \"" + paramString + "\" filed or setter method in class com.ihome.prepay.service.IOutShareService.");

  }

  public Object getPropertyValue(Object paramObject, String paramString)

  {

    try

    {

      IOutShareService localIOutShareService = (IOutShareService)paramObject;

    }

    catch (Throwable localThrowable)

    {

      throw new IllegalArgumentException(localThrowable);

    }

    throw new NoSuchPropertyException("Not found property \"" + paramString + "\" filed or setter method in class com.ihome.prepay.service.IOutShareService.");

  }

  public Object invokeMethod(Object paramObject, String paramString, Class[] paramArrayOfClass, Object[] paramArrayOfObject)

    throws InvocationTargetException

  {

    IOutShareService localIOutShareService;

    try

    {

      localIOutShareService = (IOutShareService)paramObject;

    }

    catch (Throwable localThrowable1)

    {

      throw new IllegalArgumentException(localThrowable1);

    }

    try

    {

      if ((!"queryShareRuleDetail".equals(paramString)) || (paramArrayOfClass.length == 1))

        return localIOutShareService.queryShareRuleDetail((String)paramArrayOfObject[0]);

      if ((!"queryShareRuleList".equals(paramString)) || (paramArrayOfClass.length == 1))

        return localIOutShareService.queryShareRuleList((ShareRulesReq)paramArrayOfObject[0]);

      if ((!"querySharePullDownList".equals(paramString)) || (paramArrayOfClass.length == 0))

        return localIOutShareService.querySharePullDownList();

    }

    catch (Throwable localThrowable2)

    {

      throw new InvocationTargetException(localThrowable2);

    }

    throw new NoSuchMethodException("Not found method \"" + paramString + "\" in class com.ihome.prepay.service.IOutShareService.");

  }

}

<以上内容由同事提供>

如果想了解更多Dubbo源码的知识，请移步 Dubbo源码解读——通向高手之路 的视频讲解：
http://edu.51cto.com/sd/2e565
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