dubbo-源码分析Provider

Dubbo provider启动原理：

当我们的dubbo启动我们的spring容器时spring 初始化容器的时候会查找META-INF/spring.handles文件查找对应的NamespaceHandle,dubbo在其jar包下配置了DubboNamespaceHandle,该类下有以下配置项：

registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
registerBeanDefinitionParser("config-center", new DubboBeanDefinitionParser(ConfigCenterBean.class, true));
registerBeanDefinitionParser("metadata-report", new DubboBeanDefinitionParser(MetadataReportConfig.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));
registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
registerBeanDefinitionParser("annotation", new AnnotationBeanDefinitionParser());

意思就是当spring 在解析容器的时候遇到指定配置会使用对应的Parser去解析配置项。

provider

我们提供者主要会配置对应的application、registry、protocol、service所以我们一个一个来看，我们先来看service 根据上面所说，我们配置了<dubbo:service>这个配置项的话就会生成ServiceBean对象，并注册到容器里，那我们来看下serviceBean这个类：

public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean,
        ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware,
        ApplicationEventPublisherAware

该类主要实现了上面几个接口，我们来看其中最主要的InitializingBean，该类会在类实例化后调用其中的afterPropertiesSet方法 ，所以我们来看下：

public void afterPropertiesSet() throws Exception {
   ...
    //上面一大堆代码都是判空去重新赋值的代码，我们不关注他们，最主要是下面这个export方法
    if (!supportedApplicationListener) {
        export();
    }
}

public synchronized void export() {
    checkAndUpdateSubConfigs();
​
    if (provider != null) {
        if (export == null) {
            export = provider.getExport();
        }
        if (delay == null) {
            delay = provider.getDelay();
        }
    }
    if (export != null && !export) {
        return;
    }
​
    //当设置了延时发布时用定时器延时发布
    if (delay != null && delay > 0) {
        delayExportExecutor.schedule(this::doExport, delay, TimeUnit.MILLISECONDS);
    } else {
        //否则的话直接发布
        doExport();
    }
}

export方法最主要是判断是有配置了延时发布，是的话就用schedule去延时发布，否的话doExport发布，在spring中真正干活的都是do开头的方法，我们再继续查看doExport方法

protected synchronized void doExport() {
    if (unexported) {
        throw new IllegalStateException("Already unexported!");
    }
    if (exported) {
        return;
    }
    exported = true;
​
    if (path == null || path.length() == 0) {
        path = interfaceName;
    }
    //生成唯一serviceName group/interfaceClass 如group/com.xx.xxx
    //ref 接口实现bean 服务的真正提供者
    //interfaceClass 需要发布的接口服务
    ProviderModel providerModel = new ProviderModel(getUniqueServiceName(), ref, interfaceClass);
    ApplicationModel.initProviderModel(getUniqueServiceName(), providerModel);
    //发布url
    doExportUrls();
}

这里主要查看doExportUrls()方法，上面的是把服务信息存到本地map里：

@SuppressWarnings({"unchecked", "rawtypes"})
private void doExportUrls() {
    //这里会获取到注册中心的列表如有配置多个的话,
    // 格式：registry://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=user-service&dubbo=2.0.2&pid=16232&registry=zookeeper&release=2.7.0&timestamp=1553883173387
    List<URL> registryURLs = loadRegistries(true);
    for (ProtocolConfig protocolConfig : protocols) {
        doExportUrlsFor1Protocol(protocolConfig, registryURLs);
    }
}

所以这里说明dubbo是支持多协议的多注册中心的,提前预告，下面这个doExportUrlsFor1Protocol方法会很长很复杂：

private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
    //获取协议的名称如dubbo
    String name = protocolConfig.getName();
    if (name == null || name.length() == 0) {
        //默认是dubbo
        name = Constants.DUBBO;
    }
​
    Map<String, String> map = new HashMap<String, String>();
    //组装map 再填充到url上
    map.put(Constants.SIDE_KEY, Constants.PROVIDER_SIDE);
    appendRuntimeParameters(map);
    appendParameters(map, application);
    appendParameters(map, module);
    appendParameters(map, provider, Constants.DEFAULT_KEY);
    appendParameters(map, protocolConfig);
    appendParameters(map, this);
    //这里省略了一堆设置url的代码，主要是把接口的配置方法加到参数列表里如果method 重试次数
    ....
    if (ProtocolUtils.isGeneric(generic)) {
        map.put(Constants.GENERIC_KEY, generic);
        map.put(Constants.METHODS_KEY, Constants.ANY_VALUE);
    } else {
        String revision = Version.getVersion(interfaceClass, version);
        if (revision != null && revision.length() > 0) {
            map.put("revision", revision);
        }
​
        String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
        if (methods.length == 0) {
            logger.warn("NO method found in service interface " + interfaceClass.getName());
            map.put(Constants.METHODS_KEY, Constants.ANY_VALUE);
        } else {
            map.put(Constants.METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));
        }
    }
    if (!ConfigUtils.isEmpty(token)) {
        if (ConfigUtils.isDefault(token)) {
            map.put(Constants.TOKEN_KEY, UUID.randomUUID().toString());
        } else {
            map.put(Constants.TOKEN_KEY, token);
        }
    }
    //是否injvm也就是本地发布不上注册中心
    if (Constants.LOCAL_PROTOCOL.equals(protocolConfig.getName())) {
        protocolConfig.setRegister(false);
        map.put("notify", "false");
    }
    // export service
    String contextPath = protocolConfig.getContextpath();
    if ((contextPath == null || contextPath.length() == 0) && provider != null) {
        contextPath = provider.getContextpath();
    }
​
    //获取绑定的有效IP地址
    String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
    //获得一个绑定端口
    Integer port = this.findConfigedPorts(protocolConfig, name, map);
​
    //创建一个url
    //dubbo://192.168.1.2:20882/com.lin.service.UserService?anyhost=true&application=user-service
    // &bean.name=com.lin.service.UserService&bind.ip=192.168.1.2&bind.port=20882&dubbo=2.0.2
    // &generic=false&group=userGroup&interface=com.lin.service.UserService&methods=add,findUserByName,findUserById
    // &pid=16232&release=2.7.0&side=provider&timestamp=1553884198155
    URL url = new URL(name, host, port, (contextPath == null || contextPath.length() == 0 ? "" : contextPath + "/") + path, map);
​
    if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
            .hasExtension(url.getProtocol())) {
        url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
                .getExtension(url.getProtocol()).getConfigurator(url).configure(url);
    }
​
    String scope = url.getParameter(Constants.SCOPE_KEY);
    // don't export when none is configured
    //当scope为none的时候不发布
    if (!Constants.SCOPE_NONE.equalsIgnoreCase(scope)) {
​
        // export to local if the config is not remote (export to remote only when config is remote)
        //当scope不是remote的时候发布本地服务
        if (!Constants.SCOPE_REMOTE.equalsIgnoreCase(scope)) {
            exportLocal(url);
        }
        // export to remote if the config is not local (export to local only when config is local)
        //当scope不是local的时候发布远程服务
        if (!Constants.SCOPE_LOCAL.equalsIgnoreCase(scope)) {
            if (logger.isInfoEnabled()) {
                logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
            }
            if (registryURLs != null && !registryURLs.isEmpty()) {
                //当注册中心有多个的时候会发布到多个注册中心
                for (URL registryURL : registryURLs) {
                    url = url.addParameterIfAbsent(Constants.DYNAMIC_KEY, registryURL.getParameter(Constants.DYNAMIC_KEY));
                    //监控url
                    URL monitorUrl = loadMonitor(registryURL);
                    if (monitorUrl != null) {
                        url = url.addParameterAndEncoded(Constants.MONITOR_KEY, monitorUrl.toFullString());
                    }
                    if (logger.isInfoEnabled()) {
                        logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
                    }
​
                    // For providers, this is used to enable custom proxy to generate invoker
                    String proxy = url.getParameter(Constants.PROXY_KEY);
                    if (StringUtils.isNotEmpty(proxy)) {
                        registryURL = registryURL.addParameter(Constants.PROXY_KEY, proxy);
                    }
​
                    //proxyFactory是一个自适应的扩展点，所以是一个proxyFactory$Adaptive
                    //默认会有这几个
                    //stub=org.apache.dubbo.rpc.proxy.wrapper.StubProxyFactoryWrapper
                    //jdk=org.apache.dubbo.rpc.proxy.jdk.JdkProxyFactory
                    //javassist=org.apache.dubbo.rpc.proxy.javassist.JavassistProxyFactory
                    //当url里有proxy=xxx的时候就取xxxProxyFactory,如果没有的话默认就是JavassistProxyFactory
                    Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
                    //创建一个Invoker的包装类DelegateProviderMetaDataInvoker
                    DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
                    //protocol是一个自动扩展点，所以会返回一个ivoker.getURL().protocol/Protocol的一个对象 如RegistryProtocol、DubboProtocol
                    Exporter<?> exporter = protocol.export(wrapperInvoker);
                    exporters.add(exporter);
                }
            } else {
                Invoker<?> invoker = proxyFactory.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
             */
            MetadataReportService metadataReportService = null;
            if ((metadataReportService = getMetadataReportService()) != null) {
                //上报元数据中心
                metadataReportService.publishProvider(url);
            }
        }
    }
    this.urls.add(url);
}

这里涉及到一个自适应扩展点的概念，具体什么是自适应扩展点可以到dubbo官网上看，那里介绍的很详细

因为这里要注册的URL是registry://192.168.xxxx这样格式的，又因为protocol又是一个Protocol自适应扩展点

  private static final Protocol protocol = ExtensionLoader.getExtensionLoader(Protocol.class).getAdaptiveExtension();
​
​
Exporter<?> exporter = protocol.export(wrapperInvoker);

所以我们能得到protocol.export这里里面是调用的RegistryProtocol里面的export方法，所以我们再来看下这个方法：

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
    //获得注册地址
    //zookeeper://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=user-service...
    URL registryUrl = getRegistryUrl(originInvoker);
    // url to export locally
    //获取提供者发布url
    //dubbo://192.168.1.2:20882/com.lin.service.UserService?anyhost=true&application=user-service&bean.name=...
    URL providerUrl = getProviderUrl(originInvoker);
​
    // Subscribe the override data
    // FIXME When the provider subscribes, it will affect the scene : a certain JVM exposes the service and call
    //  the same service. Because the subscribed is cached key with the name of the service, it causes the
    //  subscription information to cover.
​
    final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
    final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
    overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
​
    providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
    //export invoker
    //本地发布服务 也就是服务发布到netty容器里
    final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);
​
    // url to registry
    //获得注册中心地址
    final Registry registry = getRegistry(originInvoker);
    //获得要注册的提供者URL
    final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl, registryUrl);
    ProviderInvokerWrapper<T> providerInvokerWrapper = ProviderConsumerRegTable.registerProvider(originInvoker,
            registryUrl, registeredProviderUrl);
    //to judge if we need to delay publish
    boolean register = registeredProviderUrl.getParameter("register", true);
    if (register) {
        //注册到注册中心
        register(registryUrl, registeredProviderUrl);
        providerInvokerWrapper.setReg(true);
    }
​
    // Deprecated! Subscribe to override rules in 2.6.x or before.
    //订阅url
    registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
​
    exporter.setRegisterUrl(registeredProviderUrl);
    exporter.setSubscribeUrl(overrideSubscribeUrl);
    //Ensure that a new exporter instance is returned every time export
    return new DestroyableExporter<>(exporter);
}

我们一步一步来分析上面的代码，首先我这边的注册中心用的是zookeeper所以拿到的注册地址是zookeeper协议的，服务提供者也是用的默认的dubbo协议，那我们下一步来看下服务真正发布的方法doLocalExport方法:

private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker, URL providerUrl) {
    String key = getCacheKey(originInvoker);
    ExporterChangeableWrapper<T> exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
    if (exporter == null) {
        synchronized (bounds) {
            exporter = (ExporterChangeableWrapper<T>) bounds.get(key);
            if (exporter == null) {
​
                final Invoker<?> invokerDelegete = new InvokerDelegate<T>(originInvoker, providerUrl);
                //这里protocol又是一个自适应扩展点，所以里面会调用invoker.getUrl.getProtocol+"Protocol"的export()方法
                //如 DubboProtocol.export();
                exporter = new ExporterChangeableWrapper<T>((Exporter<T>) protocol.export(invokerDelegete), originInvoker);
                bounds.put(key, exporter);
            }
        }
    }
    return exporter;
}

一开始就是一个双重检查锁，我们不管他，直接关注我们的protocol.export方法，跟上面的一样，protocol也是一个自适应扩展点，所以里面实际用的是我们invoker.getUrl.getProtocol+"Protocol"的export()方法，我们invoker的url呢又是我们上面包装进去的providerUrl也就是dubbo://xxxx这个url，所以最终调用的就是DubboProtocol的export方法:

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
    URL url = invoker.getUrl();
​
    // export service.
    String key = serviceKey(url);
    DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
    exporterMap.put(key, exporter);
​
    //export an stub service for dispatching event
    Boolean isStubSupportEvent = url.getParameter(Constants.STUB_EVENT_KEY, Constants.DEFAULT_STUB_EVENT);
    Boolean isCallbackservice = url.getParameter(Constants.IS_CALLBACK_SERVICE, false);
    if (isStubSupportEvent && !isCallbackservice) {
        String stubServiceMethods = url.getParameter(Constants.STUB_EVENT_METHODS_KEY);
        if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
            if (logger.isWarnEnabled()) {
                logger.warn(new IllegalStateException("consumer [" + url.getParameter(Constants.INTERFACE_KEY) +
                        "], has set stubproxy support event ,but no stub methods founded."));
            }
        } else {
            stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
        }
    }
​
    openServer(url);
    optimizeSerialization(url);
    return exporter;
}

上面那些代码我们不关心先不看了，我们直接可以看到有一个openServer(url)的方法，根据名字我们就可以猜到这里就是开启我们服务的地方了，我们来看下：

private void openServer(URL url) {
    // find server.
    String key = url.getAddress();
    //client can export a service which's only for server to invoke
    boolean isServer = url.getParameter(Constants.IS_SERVER_KEY, true);
    if (isServer) {
        ExchangeServer server = serverMap.get(key);
        if (server == null) {
            synchronized (this) {
                server = serverMap.get(key);
                if (server == null) {
                    //创建服务
                    serverMap.put(key, createServer(url));
                }
            }
        } else {
            // server supports reset, use together with override
            server.reset(url);
        }
    }
}

private ExchangeServer createServer(URL url) {
    
   ...
    url = url.addParameter(Constants.CODEC_KEY, DubboCodec.NAME);
    ExchangeServer server;
    try {
        server = Exchangers.bind(url, requestHandler);
    } catch (RemotingException e) {
        throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);
    }
    ...
    return server;
}

我们可以看到这里Exchangers.bind(url,requestHandler)，这里呢最终会调到：

public static Server bind(URL url, ChannelHandler... handlers) throws RemotingException {
    if (url == null) {
        throw new IllegalArgumentException("url == null");
    }
    if (handlers == null || handlers.length == 0) {
        throw new IllegalArgumentException("handlers == null");
    }
    ChannelHandler handler;
    if (handlers.length == 1) {
        handler = handlers[0];
    } else {
        handler = new ChannelHandlerDispatcher(handlers);
    }
    //这里getTransporter也是获得一个自适应的扩展点，如果没有配置的话默认就是用的NettyTransporter
    return getTransporter().bind(url, handler);
}

再里面就是发布到Netty容器了，有兴趣的可以自己去看下，现在这里我们的服务就已经发布了，下面还有注册到注册中心，我们再看下我们上面的RegistryProtocol的export方法里面的注册服务的代码：

// url to registry
//获得注册中心地址
final Registry registry = getRegistry(originInvoker);
//获得要注册的提供者URL
final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl, registryUrl);
ProviderInvokerWrapper<T> providerInvokerWrapper = ProviderConsumerRegTable.registerProvider(originInvoker,
        registryUrl, registeredProviderUrl);
//to judge if we need to delay publish
boolean register = registeredProviderUrl.getParameter("register", true);
if (register) {
    //注册到注册中心
    register(registryUrl, registeredProviderUrl);
    providerInvokerWrapper.setReg(true);
}

主要还是register这个方法：

public void register(URL registryUrl, URL registeredProviderUrl) {
    //因为registryFacotry是一个自适应的扩展点，所以会返回一个zookeeperRegistry,如果是redis://的话就返回一个RedisRegistry
    Registry registry = registryFactory.getRegistry(registryUrl);
    //注册到注册中心
    registry.register(registeredProviderUrl);
}

根据环境我们会获得一个ZookeeperRegistry所以我们再看下zookeeperRegistry的register方法：

因为register这个方法zookeeperRegistry并没有去实现它，所以一定是在父类的register我们继续看他父类FailbackRegistry的register方法：

public void register(URL url) {
    super.register(url);
    removeFailedRegistered(url);
    removeFailedUnregistered(url);
    try {
        // Sending a registration request to the server side
        //注册服务 是模版模式，所以会在子类实现
        doRegister(url);
    } catch (Exception e) {
        Throwable t = e;
​
        // If the startup detection is opened, the Exception is thrown directly.
        boolean check = getUrl().getParameter(Constants.CHECK_KEY, true)
                && url.getParameter(Constants.CHECK_KEY, true)
                && !Constants.CONSUMER_PROTOCOL.equals(url.getProtocol());
        boolean skipFailback = t instanceof SkipFailbackWrapperException;
        if (check || skipFailback) {
            if (skipFailback) {
                t = t.getCause();
            }
            throw new IllegalStateException("Failed to register " + url + " to registry " + getUrl().getAddress() + ", cause: " + t.getMessage(), t);
        } else {
            logger.error("Failed to register " + url + ", waiting for retry, cause: " + t.getMessage(), t);
        }
​
        // Record a failed registration request to a failed list, retry regularly
        addFailedRegistered(url);
    }
}

这方法主要注册的就是doRegister方法了，因为是模版模式，所以这个方法zookeeperRegistry自己实现了这个方法：

@Override
public void doRegister(URL url) {
    try {
        //创建一个临时节点
        zkClient.create(toUrlPath(url), url.getParameter(Constants.DYNAMIC_KEY, true));
    } catch (Throwable e) {
        throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
    }
}

所以这里就是最终注册的地方了，这里会根据url去创建一个服务的临时节点，到这服务的发布和注册就已经完成了，其他地方有兴趣的可以自己去看下源码，dubbo里很多地方都用到了自适应扩展点这个概念，所以如果要看源码就要先去理解什么是自适应扩展点。