dubbo 源码学习1 服务发布机制

　1.源码版本：2.6.1

　　

源码demo中采用的是xml式的发布方式，在dubbo的 DubboNamespaceHandler 中定义了Spring Framework 的扩展标签，即 <dubbo:service> 等，dubbo通过DubboBeanDefinitionParser将不同的标签分别解析到不同的bean中，

• application 对应ApplicationConfig
• registry 对应RegistryConfig
• monitor 对应MonitorConfig
• provider 对应ProviderConfig
• consumer 对应ConsumerConfig
• protocol 对应ProtocolConfig
• service 对应ServiceBean
• reference 对应ReferenceBean
• annotation对应AnnotationBean

在spring启动服务时，dubbo通过ServiceBean收集相关配置信息，并保存到ServiceConfig中。

ServiceBean 实现 InitializingBean 接口，在spring加载完bean之后执行

public void afterPropertiesSet() throws Exception {
        if (getProvider() == null) {
            Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false);
            if (providerConfigMap != null && providerConfigMap.size() > 0) {
                Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
                if ((protocolConfigMap == null || protocolConfigMap.size() == 0)
                        && providerConfigMap.size() > 1) { // backward compatibility
                    List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
                    for (ProviderConfig config : providerConfigMap.values()) {
                        if (config.isDefault() != null && config.isDefault().booleanValue()) {
                            providerConfigs.add(config);
                        }
                    }
                    if (providerConfigs.size() > 0) {
                        setProviders(providerConfigs);
                    }
                } else {
                    ProviderConfig providerConfig = null;
                    for (ProviderConfig config : providerConfigMap.values()) {
                        if (config.isDefault() == null || config.isDefault().booleanValue()) {
                            if (providerConfig != null) {
                                throw new IllegalStateException("Duplicate provider configs: " + providerConfig + " and " + config);
                            }
                            providerConfig = config;
                        }
                    }
                    if (providerConfig != null) {
                        setProvider(providerConfig);
                    }
                }
            }
        }
        if (getApplication() == null
                && (getProvider() == null || getProvider().getApplication() == null)) {
            Map<String, ApplicationConfig> applicationConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ApplicationConfig.class, false, false);
            if (applicationConfigMap != null && applicationConfigMap.size() > 0) {
                ApplicationConfig applicationConfig = null;
                for (ApplicationConfig config : applicationConfigMap.values()) {
                    if (config.isDefault() == null || config.isDefault().booleanValue()) {
                        if (applicationConfig != null) {
                            throw new IllegalStateException("Duplicate application configs: " + applicationConfig + " and " + config);
                        }
                        applicationConfig = config;
                    }
                }
                if (applicationConfig != null) {
                    setApplication(applicationConfig);
                }
            }
        }
        if (getModule() == null
                && (getProvider() == null || getProvider().getModule() == null)) {
            Map<String, ModuleConfig> moduleConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ModuleConfig.class, false, false);
            if (moduleConfigMap != null && moduleConfigMap.size() > 0) {
                ModuleConfig moduleConfig = null;
                for (ModuleConfig config : moduleConfigMap.values()) {
                    if (config.isDefault() == null || config.isDefault().booleanValue()) {
                        if (moduleConfig != null) {
                            throw new IllegalStateException("Duplicate module configs: " + moduleConfig + " and " + config);
                        }
                        moduleConfig = config;
                    }
                }
                if (moduleConfig != null) {
                    setModule(moduleConfig);
                }
            }
        }
        if ((getRegistries() == null || getRegistries().size() == 0)
                && (getProvider() == null || getProvider().getRegistries() == null || getProvider().getRegistries().size() == 0)
                && (getApplication() == null || getApplication().getRegistries() == null || getApplication().getRegistries().size() == 0)) {
            Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false);
            if (registryConfigMap != null && registryConfigMap.size() > 0) {
                List<RegistryConfig> registryConfigs = new ArrayList<RegistryConfig>();
                for (RegistryConfig config : registryConfigMap.values()) {
                    if (config.isDefault() == null || config.isDefault().booleanValue()) {
                        registryConfigs.add(config);
                    }
                }
                if (registryConfigs != null && registryConfigs.size() > 0) {
                    super.setRegistries(registryConfigs);
                }
            }
        }
        if (getMonitor() == null
                && (getProvider() == null || getProvider().getMonitor() == null)
                && (getApplication() == null || getApplication().getMonitor() == null)) {
            Map<String, MonitorConfig> monitorConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MonitorConfig.class, false, false);
            if (monitorConfigMap != null && monitorConfigMap.size() > 0) {
                MonitorConfig monitorConfig = null;
                for (MonitorConfig config : monitorConfigMap.values()) {
                    if (config.isDefault() == null || config.isDefault().booleanValue()) {
                        if (monitorConfig != null) {
                            throw new IllegalStateException("Duplicate monitor configs: " + monitorConfig + " and " + config);
                        }
                        monitorConfig = config;
                    }
                }
                if (monitorConfig != null) {
                    setMonitor(monitorConfig);
                }
            }
        }
        if ((getProtocols() == null || getProtocols().size() == 0)
                && (getProvider() == null || getProvider().getProtocols() == null || getProvider().getProtocols().size() == 0)) {
            Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
            if (protocolConfigMap != null && protocolConfigMap.size() > 0) {
                List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>();
                for (ProtocolConfig config : protocolConfigMap.values()) {
                    if (config.isDefault() == null || config.isDefault().booleanValue()) {
                        protocolConfigs.add(config);
                    }
                }
                if (protocolConfigs != null && protocolConfigs.size() > 0) {
                    super.setProtocols(protocolConfigs);
                }
            }
        }
        if (getPath() == null || getPath().length() == 0) {
            if (beanName != null && beanName.length() > 0
                    && getInterface() != null && getInterface().length() > 0
                    && beanName.startsWith(getInterface())) {
                setPath(beanName);
            }
        }
        if (!isDelay()) {
            export();
        }
    }

在此方法中，收集相关信息，并将信息保存到继承的ServiceConfig中，然后调用ServiceConfig的 export() 方法来发布服务。 export() 方法调用一系列的判断检查方法之后，最终使用 Protocol 接口的

/**
     * Export service for remote invocation: <br>
     * 1. Protocol should record request source address after receive a request:
     * RpcContext.getContext().setRemoteAddress();<br>
     * 2. export() must be idempotent, that is, there's no difference between invoking once and invoking twice when
     * export the same URL<br>
     * 3. Invoker instance is passed in by the framework, protocol needs not to care <br>
     *
     * @param <T>     Service type
     * @param invoker Service invoker
     * @return exporter reference for exported service, useful for unexport the service later
     * @throws RpcException thrown when error occurs during export the service, for example: port is occupied
     */
    @Adaptive
    <T> Exporter<T> export(Invoker<T> invoker) throws RpcException;

方法来执行最终服务发布。 这里的 export() 是一个扩展点方法，采用动态适配加载机制，这一部分后续再说。这里最终在发布服务时使用的是  RegistryProtocol 的

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
　　　　 //export invoker
　　　　 //执行本地发布
        final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);

        URL registryUrl = getRegistryUrl(originInvoker);

        //registry provider
        final Registry registry = getRegistry(originInvoker);
        final URL registedProviderUrl = getRegistedProviderUrl(originInvoker);

        //to judge to delay publish whether or not
　　　　 //是否延时
        boolean register = registedProviderUrl.getParameter("register", true);

        ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registedProviderUrl);

        if (register) {
            register(registryUrl, registedProviderUrl);
            ProviderConsumerRegTable.getProviderWrapper(originInvoker).setReg(true);
        }

        // 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(registedProviderUrl);
        final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
        overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);

　　　　 //发布并注册zk
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
        //Ensure that a new exporter instance is returned every time export
        return new Exporter<T>() {
            public Invoker<T> getInvoker() {
                return exporter.getInvoker();
            }

            public void unexport() {
                try {
                    exporter.unexport();
                } catch (Throwable t) {
                    logger.warn(t.getMessage(), t);
                }
                try {
                    registry.unregister(registedProviderUrl);
                } catch (Throwable t) {
                    logger.warn(t.getMessage(), t);
                }
                try {
                    overrideListeners.remove(overrideSubscribeUrl);
                    registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener);
                } catch (Throwable t) {
                    logger.warn(t.getMessage(), t);
                }
            }
        };
    }

但是，如果这里执行的是本地发布，在执行到 ProtocolFilterWrapper

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
　　 // 远程发布
    if (Constants.REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
        return protocol.export(invoker);
    }
    return protocol.export(buildInvokerChain(invoker, Constants.SERVICE_FILTER_KEY, Constants.PROVIDER));
}

时，会使用 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;
    }

通过 openServer(url); 开启Netty服务，并判断server是否存在，若不存在则创建新的服务。

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) {
                serverMap.put(key, createServer(url));
            } else {
                // server supports reset, use together with override
                server.reset(url);
            }
        }
    }

createServer 时，Exchangers的 bind() 方法 getExchanger(url) 得到的默认为 HeaderExchanger，HeaderExchanger 的 bind() 方法又调用了 Transporters 中的 bind() 方法，getTransporter() 方法擦用适配加载机制，

Transporter类的注解为@SPI("netty")，默认会调用 NettyTransporter 的 bind() 方法，NettyTransporter 的 bind() 方法直接new了一个 NettyServer，NettyServer 初始化的时候调用父类的构造方法，父类的构造方法中调用了 NettyServer 的 doOpen() 方法，

NettyServer 的链接创建在 doOpen() 方法中完成。

public Server bind(URL url, ChannelHandler listener) throws RemotingException {
        return new NettyServer(url, listener);
    }

protected void doOpen() throws Throwable {
        NettyHelper.setNettyLoggerFactory();
        ExecutorService boss = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerBoss", true));
        ExecutorService worker = Executors.newCachedThreadPool(new NamedThreadFactory("NettyServerWorker", true));
        ChannelFactory channelFactory = new NioServerSocketChannelFactory(boss, worker, getUrl().getPositiveParameter(Constants.IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS));
        bootstrap = new ServerBootstrap(channelFactory);

        final NettyHandler nettyHandler = new NettyHandler(getUrl(), this);
        channels = nettyHandler.getChannels();
        // https://issues.jboss.org/browse/NETTY-365
        // https://issues.jboss.org/browse/NETTY-379
        // final Timer timer = new HashedWheelTimer(new NamedThreadFactory("NettyIdleTimer", true));
        bootstrap.setPipelineFactory(new ChannelPipelineFactory() {
            public ChannelPipeline getPipeline() {
                NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this);
                ChannelPipeline pipeline = Channels.pipeline();
                /*int idleTimeout = getIdleTimeout();
                if (idleTimeout > 10000) {
                    pipeline.addLast("timer", new IdleStateHandler(timer, idleTimeout / 1000, 0, 0));
                }*/
                pipeline.addLast("decoder", adapter.getDecoder());
                pipeline.addLast("encoder", adapter.getEncoder());
                pipeline.addLast("handler", nettyHandler);
                return pipeline;
            }
        });
        // bind
        channel = bootstrap.bind(getBindAddress());
    }

如果不是本地发布

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
        //export invoker
        // 在本地暴露服务
        final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker);
        //registry provider
        // 拿到zookeeper的注册信息
        URL registryUrl = getRegistryUrl(originInvoker);

        //registry provider
        // 获取需要暴露provider的url对象，以url作为参数传递的
        final Registry registry = getRegistry(originInvoker);
        final URL registedProviderUrl = getRegistedProviderUrl(originInvoker);

        //to judge to delay publish whether or not
        //是否延迟发布
        boolean register = registedProviderUrl.getParameter("register", true);

        ProviderConsumerRegTable.registerProvider(originInvoker, registryUrl, registedProviderUrl);

        //如果延迟发布，启用新的
        if (register) {
            register(registryUrl, registedProviderUrl);
            ProviderConsumerRegTable.getProviderWrapper(originInvoker).setReg(true);
        }

        // 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(registedProviderUrl);
        final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
        overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
        // 暴露的同时订阅服务，在zk上创建configurators节点信息
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);

        //保证每次export都返回一个新的exporter实例
        return new Exporter<T>() {
            public Invoker<T> getInvoker() {
                return exporter.getInvoker();
            }

            public void unexport() {
                try {
                    exporter.unexport();
                } catch (Throwable t) {
                    logger.warn(t.getMessage(), t);
                }
                try {
                    registry.unregister(registedProviderUrl);
                } catch (Throwable t) {
                    logger.warn(t.getMessage(), t);
                }
                try {
                    overrideListeners.remove(overrideSubscribeUrl);
                    registry.unsubscribe(overrideSubscribeUrl, overrideSubscribeListener);
                } catch (Throwable t) {
                    logger.warn(t.getMessage(), t);
                }
            }
        };
    }

最后吐槽一下，开放出来的源码不符合p3c......