Dubbo的源码分析(四)
一. Dubbo服务的注册流程
服务发布步骤
我们前面做的项目,如果要发布一个项目要做两件事,第一件,配置了注解@DubboService(loadbalance = "random",cluster = "failover",retries = 2);第二件是配置了注解扫描@DubboComponentScan;由这我们可能会想,这个注解扫描是怎么进行扫描和解析的,扫描哪些类;注解是怎么把服务注册到注册中心的;前面我们讲过缓存,当中心挂了之后服务依然能从缓存的URL路径中找到要调用的服务路径信息,那么这里面URL驱动是怎么完成的,他们的URL路径又是怎么组装的等等这些问题;下面我就提出的这些问题来进行探究;
dubbo源码
有了上面的疑问,我们就有了一个看代码的基本思路,我个人觉得看代码和我们建框架样,不能一来就去扣细节不放,我们在了解一个新的事务时一定是先看主线,了解了主线后再慢慢扩展到分支和细节;说了这么多接下来我们就进入源码分析;dubbo服务发布有两种形式,第一种是xml 形式 <dubbo:service>形式,另一种是注解形式;我们现在都喜欢用注解了,所以我主要分析我看的注解形式的源码
注解解析流程
我们看下@DubboComponentScan(basePackages = "com.ghy.spring.dubbo.springbootserver.service")里面定义的是什么东西,点击进去发现会导入一个DubboComponentScanRegistrar类;他是动态注册Bean的类,通过这个Bean的注册类会把Bean注册到IOC容器类,如果感觉兴趣的可以自己去看下IOC容器的源码,后面我有空也会写spring源码的解析过程
点击进去看下,首先得到了一个getPackagesToScan;这个是我们在源数据中定义的@DubboComponentScan(basePackages = "com.ghy.spring.dubbo.springbootserver.service")中的basePackages;看到这里大家应该就明白 basePackages为什么可以配置多个了;
接着向下跟进registerServiceAnnotationBeanPostProcessor(packagesToScan, registry);看它注册了一个什么Bean;通过下图我们发现它注册的是ServiceAnnotationBeanPostProcessor这个Bean,并且在构造这个Bean时将packagesToScan传递进去了;看到这里我们应该就能猜到服务的注册流程应该和ServiceAnnotationBeanPostProcessor有关系; 在IOC容器注册完成后,会有方法调用ServiceAnnotationBeanPostProcessor做些事情进行解析里面的类的注解方法。它把这个Bean传过去个会调用BeanDefinitionReaderUtils.registerWithGeneratedName(beanDefinition, registry);注册这个Bean的beanDefinition;
在Dubbo中除了@DubboComponentScan会加载Bean外还有一个类会加载Ben,那就是DubboAutoConfiguration类;为了避免重复加载,他加了一个@ConditionalOnBean注解,通过观察我们发现这个Bean的加载方法和我们前面讲的有一个共同点那就是都有一个ServiceAnnotationBeanPostProcessor类;我们可以点进去看下
进来我们首先发现了@Deprecated标签,说明这是一个过期的;在里面我们可以在他的构造方法中发现传入了packagesToScan,bean装载完成之后,会触发下面这个方法.我们点super进去看下
进去后发现他实现了BeanDefinitionRegistryPostProcessor接口重写了postProcessBeanDefinitionRegistry方法;
这里面我们关注注册基础Bean的registerBeans(registry, DubboBootstrapApplicationListener.class);和注册serverBean的registerServiceBeans(resolvedPackagesToScan, registry);这两个方法就行
其中基础Bean应该是把DubboBootstrapApplicationListener注册进去了,我们点击进去看下;进去之后会发现里面有一个监听,里面会监听两个东西,一个是事件
ContextRefreshedEvent,这个是在Bean上下文装载完成后进行触发;另一个是ContextClosedEvent
看完上面我们回退到postProcessBeanDefinitionRegistry方法中,我们发现当我们传入的resolvedPackagesToScan不为空时为调用registerServiceBeans(resolvedPackagesToScan, registry);
点击进去
private void registerServiceBeans(Set<String> packagesToScan, BeanDefinitionRegistry registry) { //扫描的 DubboClassPathBeanDefinitionScanner scanner = new DubboClassPathBeanDefinitionScanner(registry, environment, resourceLoader); //生成一个BEAN名称的 BeanNameGenerator beanNameGenerator = resolveBeanNameGenerator(registry); scanner.setBeanNameGenerator(beanNameGenerator); //为了兼容老的版本,实际上就是把需要扫描的注解类型,设置到scanner // refactor @since 2.7.7 serviceAnnotationTypes.forEach(annotationType -> { scanner.addIncludeFilter(new AnnotationTypeFilter(annotationType)); }); for (String packageToScan : packagesToScan) { // Registers @Service Bean first scanner.scan(packageToScan); // Finds all BeanDefinitionHolders of @Service whether @ComponentScan scans or not. Set<BeanDefinitionHolder> beanDefinitionHolders = findServiceBeanDefinitionHolders(scanner, packageToScan, registry, beanNameGenerator); if (!CollectionUtils.isEmpty(beanDefinitionHolders)) { for (BeanDefinitionHolder beanDefinitionHolder : beanDefinitionHolders) {
//这是扫描注解的过程,可以跟进看下 registerServiceBean(beanDefinitionHolder, registry, scanner); } if (logger.isInfoEnabled()) { logger.info(beanDefinitionHolders.size() + " annotated Dubbo's @Service Components { " + beanDefinitionHolders + " } were scanned under package[" + packageToScan + "]"); } } else { if (logger.isWarnEnabled()) { logger.warn("No Spring Bean annotating Dubbo's @Service was found under package[" + packageToScan + "]"); } } } }
private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry, DubboClassPathBeanDefinitionScanner scanner) { Class<?> beanClass = resolveClass(beanDefinitionHolder); Annotation service = findServiceAnnotation(beanClass); /** * The {@link AnnotationAttributes} of @Service annotation */ AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false); Class<?> interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass); String annotatedServiceBeanName = beanDefinitionHolder.getBeanName(); //首先我们可以看到他注册的是一个serviceBeanDefinition,传递的参数是serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName //至于是怎么注册的我们跟进buildServiceBeanDefinition看他是怎么组装的 AbstractBeanDefinition serviceBeanDefinition = buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName); // ServiceBean Bean name String beanName = generateServiceBeanName(serviceAnnotationAttributes, interfaceClass); if (scanner.checkCandidate(beanName, serviceBeanDefinition)) { // check duplicated candidate bean registry.registerBeanDefinition(beanName, serviceBeanDefinition); if (logger.isInfoEnabled()) { logger.info("The BeanDefinition[" + serviceBeanDefinition + "] of ServiceBean has been registered with name : " + beanName); } } else { if (logger.isWarnEnabled()) { logger.warn("The Duplicated BeanDefinition[" + serviceBeanDefinition + "] of ServiceBean[ bean name : " + beanName + "] was be found , Did @DubboComponentScan scan to same package in many times?"); } } }
通过上面我们可以知道他注入的bean源头是AbstractBeanDefinition serviceBeanDefinition =buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName);
点击buildServiceBeanDefinition进入;进来第一眼我们就可以看到他把很多构造的Bean的信息放到ServiceBean.class中,这一步相当于将ServiceBean注册到IOC容器中去了
接着registerServiceBean向下看里面都是构造的构造和赋值的过程构造完成后他最终注册的Bean是registry.registerBeanDefinition(beanName, serviceBeanDefinition);
ServiceBean的初始化阶段
最终通过上述代码,将一个 dubbo中提供的ServiceBean注入到Spring IOC容器;IOC容器的注入本质上就是对Bean的初始化,我们注入一个Bean就会对他进行
初始化,初始化完成后我们就可以对他进行调用,我们进入到serverBean中看下就可以发现这个bean被注入后就是实例化了
前面动作我们是完成了注解的扫描、配置的加载以及注册一个serverBean,serverBean注册完成后就进入到上图位置;当进入到初始化阶段会做两间事
public ServiceBean() { super(); this.service = null; }
当ServiceBean初始化完成之后,会调用下面的方法.
@Override public void afterPropertiesSet() throws Exception { if (StringUtils.isEmpty(getPath())) { if (StringUtils.isNotEmpty(beanName) && StringUtils.isNotEmpty(getInterface()) && beanName.startsWith(getInterface())) { setPath(beanName); } } }
上面的程序中我们要关心的点是ServiceBean是干嘛的,我们看下面代码发现在Dubbo中有两个BEAN比较核心,一个是serviceBean另一个是ReferenceBean
其实service是服务的发布,reference是动态代理引入;点击ServiceBean类中的super()进入下图
我们现在走到这一步感觉不知道怎么向下走了,这时我们换一个思维,我们想springBean在BEAN加载完成后是不是要触发监听,这个思维我们在开发中可以引用;这时我们应该想到前面我说过的
DubboBootstrapApplicationListener,这个监听会帮我们启动服务
点进去看一下,在看之前我们想一下这个start会帮我们做什么,我们见名知意,可能会想,这个逻辑会不会是完成我们开篇写的一些猜想,完成URL拼接,服务注册及启动INetty server及元数据初始化啥的呢,
我想说的是,对的,在这里面他会完成这些事情,至于怎么完成的,我们慢慢来聊
/** * Start the bootstrap */ public DubboBootstrap start() { if (started.compareAndSet(false, true)) { ready.set(false); //初始化,可以跟进去看一看 initialize(); if (logger.isInfoEnabled()) { logger.info(NAME + " is starting..."); } //发布DUBBO服务 // 1. export Dubbo Services exportServices(); // Not only provider register if (!isOnlyRegisterProvider() || hasExportedServices()) { //暴露本地元数据服务 // 2. export MetadataService exportMetadataService(); //注册服务实例;这里面的注册绝对是将dubbo的服务注册到一个专用的 //服务中心 //3. Register the local ServiceInstance if required registerServiceInstance(); } //处理消费者的操作 referServices(); if (asyncExportingFutures.size() > 0) { new Thread(() -> { try { this.awaitFinish(); } catch (Exception e) { logger.warn(NAME + " exportAsync occurred an exception."); } ready.set(true); if (logger.isInfoEnabled()) { logger.info(NAME + " is ready."); } }).start(); } else { ready.set(true); if (logger.isInfoEnabled()) { logger.info(NAME + " is ready."); } } if (logger.isInfoEnabled()) { logger.info(NAME + " has started."); } } return this; }
下面这段代码我们先了解下有个概念就可以
private void initialize() { if (!initialized.compareAndSet(false, true)) { return; } //维护我们一些信息,配置管理和模型信息 ApplicationModel.initFrameworkExts(); startConfigCenter(); //服务注册信息 useRegistryAsConfigCenterIfNecessary(); loadRemoteConfigs(); checkGlobalConfigs(); //初始化元数据 initMetadataService(); //初始化监听 initEventListener(); if (logger.isInfoEnabled()) { logger.info(NAME + " has been initialized!"); } }
服务的发布
我们回退一步进入exportServices();
//在这里拼接URL如果是dubbo协议会启动netty server private void exportServices() { //configManager这里面会管理我们发布服务的列表 configManager.getServices().forEach(sc -> { // TODO, compatible with ServiceConfig.export() ServiceConfig serviceConfig = (ServiceConfig) sc; serviceConfig.setBootstrap(this); if (exportAsync) { //异步发布 ExecutorService executor = executorRepository.getServiceExporterExecutor(); Future<?> future = executor.submit(() -> { //跟进去 sc.export(); exportedServices.add(sc); }); asyncExportingFutures.add(future); } else { //同步发布 sc.export(); exportedServices.add(sc); } }); }
//调用的是ServiceConfig中的方法
public synchronized void export() { //是否应该发布 if (!shouldExport()) { return; } //bootstrap是否初始化了,没有就初始化 if (bootstrap == null) { bootstrap = DubboBootstrap.getInstance(); bootstrap.init(); } //检查配置信息 checkAndUpdateSubConfigs(); //初始化元数据 //init serviceMetadata serviceMetadata.setVersion(version); serviceMetadata.setGroup(group); serviceMetadata.setDefaultGroup(group); serviceMetadata.setServiceType(getInterfaceClass()); serviceMetadata.setServiceInterfaceName(getInterface()); serviceMetadata.setTarget(getRef()); //是否延时启动 if (shouldDelay()) { DELAY_EXPORT_EXECUTOR.schedule(this::doExport, getDelay(), TimeUnit.MILLISECONDS); } else { doExport(); } //发布 exported(); }
进入doExport,这里面没啥我们直接进入doExportUrls();
protected synchronized void doExport() { if (unexported) { throw new IllegalStateException("The service " + interfaceClass.getName() + " has already unexported!"); } if (exported) { return; } exported = true; if (StringUtils.isEmpty(path)) { path = interfaceName; } doExportUrls(); }
doExportUrls()这里面是进行服务的发布,发布URL
// 主要流程,根据开发者配置的协议列表,遍历协议列表逐项进行发布。
private void doExportUrls() { ServiceRepository repository = ApplicationModel.getServiceRepository(); ServiceDescriptor serviceDescriptor = repository.registerService(getInterfaceClass()); repository.registerProvider( getUniqueServiceName(), ref, serviceDescriptor, this, serviceMetadata ); //先拿注册中心的URL List<URL> registryURLs = ConfigValidationUtils.loadRegistries(this, true); //遍历协议进行发布 for (ProtocolConfig protocolConfig : protocols) { String pathKey = URL.buildKey(getContextPath(protocolConfig) .map(p -> p + "/" + path) .orElse(path), group, version); // In case user specified path, register service one more time to map it to path. repository.registerService(pathKey, interfaceClass); // TODO, uncomment this line once service key is unified serviceMetadata.setServiceKey(pathKey); //针对具体协议去发布 doExportUrlsFor1Protocol(protocolConfig, registryURLs); } }
* 生成url * 根据url中配置的协议类型,调用指定协议进行服务的发布 * 启动服务 * 注册服务 private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) { //如果协议名称为空则用默认DUBBO协议 String name = protocolConfig.getName(); if (StringUtils.isEmpty(name)) { name = DUBBO; } //用来存储所有的配置信息 * dubbo:service dubbo:method dubbo:argument Map<String, String> map = new HashMap<String, String>(); map.put(SIDE_KEY, PROVIDER_SIDE); ServiceConfig.appendRuntimeParameters(map); AbstractConfig.appendParameters(map, getMetrics()); AbstractConfig.appendParameters(map, getApplication()); AbstractConfig.appendParameters(map, getModule()); // remove 'default.' prefix for configs from ProviderConfig // appendParameters(map, provider, Constants.DEFAULT_KEY); AbstractConfig.appendParameters(map, provider); AbstractConfig.appendParameters(map, protocolConfig); AbstractConfig.appendParameters(map, this); MetadataReportConfig metadataReportConfig = getMetadataReportConfig(); if (metadataReportConfig != null && metadataReportConfig.isValid()) { map.putIfAbsent(METADATA_KEY, REMOTE_METADATA_STORAGE_TYPE); } //注解解析 if (CollectionUtils.isNotEmpty(getMethods())) { for (MethodConfig method : getMethods()) { AbstractConfig.appendParameters(map, method, method.getName()); String retryKey = method.getName() + ".retry"; if (map.containsKey(retryKey)) { String retryValue = map.remove(retryKey); if ("false".equals(retryValue)) { map.put(method.getName() + ".retries", "0"); } } List<ArgumentConfig> arguments = method.getArguments(); if (CollectionUtils.isNotEmpty(arguments)) { for (ArgumentConfig argument : arguments) { // convert argument type if (argument.getType() != null && argument.getType().length() > 0) { Method[] methods = interfaceClass.getMethods(); // visit all methods if (methods.length > 0) { for (int i = 0; i < methods.length; i++) { String methodName = methods[i].getName(); // target the method, and get its signature if (methodName.equals(method.getName())) { Class<?>[] argtypes = methods[i].getParameterTypes(); // one callback in the method if (argument.getIndex() != -1) { if (argtypes[argument.getIndex()].getName().equals(argument.getType())) { AbstractConfig.appendParameters(map, argument, method.getName() + "." + argument.getIndex()); } else { throw new IllegalArgumentException("Argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType()); } } else { // multiple callbacks in the method for (int j = 0; j < argtypes.length; j++) { Class<?> argclazz = argtypes[j]; if (argclazz.getName().equals(argument.getType())) { AbstractConfig.appendParameters(map, argument, method.getName() + "." + j); if (argument.getIndex() != -1 && argument.getIndex() != j) { throw new IllegalArgumentException("Argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType()); } } } } } } } } else if (argument.getIndex() != -1) { AbstractConfig.appendParameters(map, argument, method.getName() + "." + argument.getIndex()); } else { throw new IllegalArgumentException("Argument config must set index or type attribute.eg: <dubbo:argument index='0' .../> or <dubbo:argument type=xxx .../>"); } } } } // end of methods for } //如果是泛化的话,再添加一个参数 if (ProtocolUtils.isGeneric(generic)) { map.put(GENERIC_KEY, generic); map.put(METHODS_KEY, ANY_VALUE); } else { String revision = Version.getVersion(interfaceClass, version); if (revision != null && revision.length() > 0) { map.put(REVISION_KEY, revision); } String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames(); if (methods.length == 0) { logger.warn("No method found in service interface " + interfaceClass.getName()); map.put(METHODS_KEY, ANY_VALUE); } else { map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ",")); } } /** * Here the token value configured by the provider is used to assign the value to ServiceConfig#token */ //校验 if(ConfigUtils.isEmpty(token) && provider != null) { token = provider.getToken(); } if (!ConfigUtils.isEmpty(token)) { if (ConfigUtils.isDefault(token)) { map.put(TOKEN_KEY, UUID.randomUUID().toString()); } else { map.put(TOKEN_KEY, token); } } //init serviceMetadata attachments serviceMetadata.getAttachments().putAll(map); // export service String host = findConfigedHosts(protocolConfig, registryURLs, map);//自己DUBUGGER看下拼接的路径 Integer port = findConfigedPorts(protocolConfig, name, map); URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map); //经过上面步骤我们的注册地址就有了,但是到这一步我们的信息还是没有注册没有发布,前面的所有步骤还是停留在数据的装载和组装上 // You can customize Configurator to append extra parameters //扩展点;如果我们有要扩展的配置的话可以在这个扩展点进行扩展 if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class) .hasExtension(url.getProtocol())) { //比对 urlf替换 url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class) .getExtension(url.getProtocol()).getConfigurator(url).configure(url); } String scope = url.getParameter(SCOPE_KEY); // don't export when none is configured if (!SCOPE_NONE.equalsIgnoreCase(scope)) { // export to local if the config is not remote (export to remote only when config is remote) if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) { exportLocal(url); } // export to remote if the config is not local (export to local only when config is local) if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) { if (CollectionUtils.isNotEmpty(registryURLs)) { for (URL registryURL : registryURLs) { //if protocol is only injvm ,not register if (LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) { continue; } url = url.addParameterIfAbsent(DYNAMIC_KEY, registryURL.getParameter(DYNAMIC_KEY)); URL monitorUrl = ConfigValidationUtils.loadMonitor(this, registryURL); if (monitorUrl != null) { url = url.addParameterAndEncoded(MONITOR_KEY, monitorUrl.toFullString()); } if (logger.isInfoEnabled()) { if (url.getParameter(REGISTER_KEY, true)) { logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL); } else { logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url); } } // For providers, this is used to enable custom proxy to generate invoker String proxy = url.getParameter(PROXY_KEY); if (StringUtils.isNotEmpty(proxy)) { registryURL = registryURL.addParameter(PROXY_KEY, proxy); } Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString())); DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this); Exporter<?> exporter = PROTOCOL.export(wrapperInvoker); exporters.add(exporter); } } else { if (logger.isInfoEnabled()) { logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url); } Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, url); DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this); Exporter<?> exporter = PROTOCOL.export(wrapperInvoker); exporters.add(exporter); } /** * @since 2.7.0 * ServiceData Store */ WritableMetadataService metadataService = WritableMetadataService.getExtension(url.getParameter(METADATA_KEY, DEFAULT_METADATA_STORAGE_TYPE)); if (metadataService != null) { metadataService.publishServiceDefinition(url); } } } this.urls.add(url); }
dubbo中的扩展点
上面聊到了扩展点,下面我就dubbo的扩展点说点东西,概念的东西官网写的很详细我就不多说了http://dubbo.apache.org/zh-cn/docs/dev/impls/protocol.html ;http://dubbo.apache.org/zh-cn/docs/source_code_guide/dubbo-spi.html
对于源码的一些讲解官网上也有
dubbo中提供了三种扩展点,分别是:
- 自适应扩展点 ExtesionLoader.getExtensionLoader(protocol.class).getExtension("name")
- 指定名称扩展点 ExtesionLoader.getExtensionLoader(protocol.class).getAdaptiveExtension()
- 激活扩展点 ExtesionLoader.getExtensionLoader(protocol.class) .getAdaptiveExtension
前面有讲过负载均衡功能相信有看过的朋友应该还有印象,在讲扩展点源码前我们就负载均衡功能来实操下;首先继承AbstractLoadBalance;AbstractLoadBalance 抽象类是所有负载均衡策略实现类的父类,实现了LoadBalance接口 的方法,同时提供抽象方法交由子类实现
我扩展的是LoadBalance接口,所以文件命名也是有要求的,前面部分是LoadBalance类路径,后面是类名;文件中键值对也是有要求“=”号后面是我们扩展类的路径
=
如果想要验证可以写个测试类自己验证下