今天来简单做一下Dubbo服务注册部分源码学习手记。
一、Dubbo配置解析
目前Dubbo最多的用法就是跟Spring集成,既然跟Spring集成,那么,Dubbo对象的实例化都将交由Spring统一处理。而Dubbo配置,对于Spring来说其实就是自定标签。这里Dubbo自定义标签解析类,在Dubbo配置模块(\dubbo-config\dubbo-config-spring\src\main\resources\META-INF/spring.handlers)进行了声明:
http\://dubbo.apache.org/schema/dubbo=org.apache.dubbo.config.spring.schema.DubboNamespaceHandler
http\://code.alibabatech.com/schema/dubbo=org.apache.dubbo.config.spring.schema.DubboNamespaceHandler
1 public class DubboNamespaceHandler extends NamespaceHandlerSupport { 2 static { 3 Version.checkDuplicate(DubboNamespaceHandler.class); 4 } 5 @Override 6 public void init() { 7 registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true)); 8 registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true)); 9 registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true)); 10 registerBeanDefinitionParser("config-center", new DubboBeanDefinitionParser(ConfigCenterBean.class, true)); 11 registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true)); 12 registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true)); 13 registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true)); 14 registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true)); 15 registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true)); 16 registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false)); 17 registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser()); 18 } 19 }
对应一下Dubbo服务提供方的配置文件:
<dubbo:application name="demo-provider"/> <dubbo:registry address="zookeeper://127.0.0.1:2181" /> <dubbo:protocol name="dubbo"/> <bean id="demoService" class="org.apache.dubbo.demo.provider.DemoServiceImpl"/> <dubbo:service interface="org.apache.dubbo.demo.DemoService" ref="demoService"/>
就是将这些标签解析成ApplicationConfig...ServiceBean等等对象。而服务注册部分最主要的桥梁就在于ServiceBean初始化解析完毕的时候。有Spring容器调用ServiceBean.afterPropertiesSet方法:
1 public void afterPropertiesSet() throws Exception { 2 // 此处省略配置检查 3 export(); 4 }
二、配置检查与缺省填充
进入export方法中,首先会对ServiceBean进行发布前的配置检查与填充。
1 public synchronized void export() { 2 checkAndUpdateSubConfigs(); // 加载并更新配置信息到Bean对象中,并检查 3 }
这里会有一系列的配置校验与配置填充的逻辑:
1 public void checkAndUpdateSubConfigs() { 2 checkDefault(); 3 if (provider != null) { 4 inheritIfAbsentFromProvider(); 5 } 6 if (module != null) { 7 inheritIfAbsentFromModule(); 8 } 9 if (application != null) { 10 inheritIfAbsentFromApplication(); 11 } 12 checkApplication(); 13 checkRegistry(); 14 checkProtocol(); 15 this.refresh(); 16 checkMetadataReport(); 17 checkRegistryDataConfig(); 18 try { 19 interfaceClass = Class.forName(interfaceName, true, Thread.currentThread().getContextClassLoader()); 20 } catch (ClassNotFoundException e) { 21 throw new IllegalStateException(e.getMessage(), e); 22 } 23 checkInterfaceAndMethods(interfaceClass, methods); 24 checkRef(); 25 checkStubAndLocal(interfaceClass); 26 checkMock(interfaceClass); 27 }
这里只列了部分配置检查与填充。总体配置的区分是否配置中心优先,优先级为:
1 public void refresh() { 2 // getPrefix为对应配置类的前缀,ProviderConfig->Provider, ServiceBean->Service, 3 // getId为beanId, 4 CompositeConfiguration compositeConfiguration = Environment.getInstance().getConfiguration(getPrefix(), getId()); 5 InmemoryConfiguration config = new InmemoryConfiguration(getPrefix(), getId()); 6 config.addProperties(getMetaData()); // Bean对象的初始值 7 if (Environment.getInstance().isConfigCenterFirst()) { 8 // -D系统属性 > 配置中心应用配置 > 配置中心全局配置 > Bean对象的初始值 > 属性文件中的信息 9 compositeConfiguration.addConfiguration(3, config); 10 } else { 11 // -D > Bean对象的初始值 > 配置中心应用配置 > 配置中心全局配置 > 属性文件中的信息 12 compositeConfiguration.addConfiguration(1, config); 13 } 14 }
三、获取和构建注册中心统一资源定位器
1 private void doExportUrls() { 2 // 获取注册中心统一资源列表,如果注册中心没有初始化,则先初始化 3 ListregistryURLs = loadRegistries(true); 4 // 将目标服务所有协议模式注册到每一个注册中心上 5 for (ProtocolConfig protocolConfig : protocols) { 6 doExportUrlsFor1Protocol(protocolConfig, registryURLs); 7 } 8 }
四、服务启动与服务注册
在doExportUrlsForProtocal方法里边其实就做了以下几件事:
1 private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, ListregistryURLs) { 2 Map map = builderUrl(); 3 // 代表一个服务 4 URL url = new URL(name, host, port, (StringUtils.isEmpty(contextPath) ? "" : contextPath + "/") + path, map); 5 // 通过代理工厂将ref对象转化成invoker对象 6 Invoker> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, url); 7 //代理invoker对象 8 DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this); 9 // 使用配置协议启动、暴露服务 10 Exporter> exporter = protocol.export(wrapperInvoker); 11 //一个服务可能有多个提供者,保存在一起 12 exporters.add(exporter); 13 }
这里,我们着重看第10行服务暴露部分,这里调用export方法,如果是Dubbo协议的话,分别列举一下DubboProtocal、HttpProtocol的export:
1 public class DubboProtocol extends AbstractProtocol { 2 publicExporter export(Invoker invoker) throws RpcException { 3 URL url = invoker.getUrl(); 4 //忽略若干代码 5 //打开服务 6 openServer(url); 7 optimizeSerialization(url); 8 return exporter; 9 } 10 }
1 public class HttpProtocol extends AbstractProxyProtocol { 2 protectedRunnable doExport(final T impl, Class type, URL url) throws RpcException { 3 String addr = getAddr(url); 4 HttpServer server = serverMap.get(addr); 5 server = httpBinder.bind(url, new InternalHandler()); 6 } 7 }
其实这块就是,根据不同协议分别做了服务启动,如果是Dubbo协议则启动NettyServer,如果是Http协议则启动一个Tomcat。
那么现在服务启动了,但是在哪里注册了呢?其实我们要关注这个protocol对象的构建:
1 /** 2 * The {@link Protocol} implementation with adaptive functionality,it will be different in different scenarios. 3 * A particular {@link Protocol} implementation is determined by the protocol attribute in the {@link URL}. 4 * For example: 5 * 6 *when the url is registry://224.5.6.7:1234/org.apache.dubbo.registry.RegistryService?application=dubbo-sample, 7 * then the protocol is RegistryProtocol 8 * 9 *when the url is dubbo://224.5.6.7:1234/org.apache.dubbo.config.api.DemoService?application=dubbo-sample, then 10 * the protocol is DubboProtocol 11 *12 * Actually,when the {@link ExtensionLoader} init the {@link Protocol} instants,it will automatically wraps two 13 * layers, and eventually will get a ProtocolFilterWrapper or ProtocolListenerWrapper 14 */ 15 private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
这段源码的意思是,在获取Protocol实例的时候,Dubbo框架自动给包装了两个切面,其实服务注册就是在这个切面里边完成的:
1 public class ProtocolListenerWrapper implements Protocol { 2 private final Protocol protocol; 3 @Override 4 publicExporter export(Invoker invoker) throws RpcException { 5 //如果是registerProtocol,则调用RegisterProtocol.export方法 6 if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) { 7 return protocol.export(invoker); 8 } 9 return new ListenerExporterWrapper (protocol.export(invoker), 10 Collections.unmodifiableList(ExtensionLoader.getExtensionLoader(ExporterListener.class) 11 .getActivateExtension(invoker.getUrl(), Constants.EXPORTER_LISTENER_KEY))); 12 } 13 }
再看看RegisterProtocol的export:
1 public class RegistryProtocol implements Protocol { 2 @Override 3 publicExporter export(final Invoker originInvoker) throws RpcException { 4 register(registryUrl, registeredProviderUrl); // 服务注册 5 } 6 }
如果注册中心是ZK的话其实就是给ZK写数据:
1 @Override 2 public void register(URL url) { 3 //忽略很多代码 4 doRegister(url); 5 //忽略很多代码 6 } 7 protected void doRegister(URL url) { 8 try { 9 zkClient.create(toUrlPath(url), url.getParameter(Constants.DYNAMIC_KEY, true)); 10 } catch (Throwable e) { 11 throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e); 12 } 13 }
相关文章:https://www.jianshu.com/p/7f3871492c71