记录

记录下dubbo的主要流程

DubboBeanDefinitionParser 解析为ServiceBean,未配置延迟暴露，就在afterPropertiesSet 中export，配置了就在容器初始化完成，发ContextRefreshEvent后，在onApplicationEvent里面暴露。

方法doExportUrls如下

    private void doExportUrls() {
        List<URL> registryURLs = loadRegistries(true);
        for (ProtocolConfig protocolConfig : protocols) {
            doExportUrlsFor1Protocol(protocolConfig, registryURLs);
        }
    }

 

loadRegistries主要是生成注册中心的URL地址，如registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&pid=22567&registry=zookeeper&timestamp=1521701807532

方法doExportUrlsFor1Protocol前面部分主要是组装URL参数，不细说 ，调到核心部分

    Invoker<?> invoker = proxyFactory.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(Constants.EXPORT_KEY, url.toFullString()));
    DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);

    Exporter<?> exporter = protocol.export(wrapperInvoker);
    exporters.add(exporter);

 这里proxyFactory是合成的adaptive实现，代码如下，URL中没有参数proxy，取得是javassist实现

public class ProxyFactory$Adaptive implements com.alibaba.dubbo.rpc.ProxyFactory {
    public java.lang.Object getProxy(com.alibaba.dubbo.rpc.Invoker arg0) throws com.alibaba.dubbo.rpc.RpcException {
        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 com.alibaba.dubbo.rpc.RpcException {
        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);
    }
}

在JavassistProxyFactory里面代码如下

  public <T> Invoker<T> getInvoker(T proxy, Class<T> type, URL url) {
        // TODO Wrapper cannot handle this scenario correctly: the classname contains '$'
        final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
        return new AbstractProxyInvoker<T>(proxy, type, url) {
            @Override
            protected Object doInvoke(T proxy, String methodName,
                                      Class<?>[] parameterTypes,
                                      Object[] arguments) throws Throwable {
                return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
            }
        };
    }

在这里生成供外部调用的Invoker对象。wrapper是字节码拼装的对象，wrapper.invokeMethod 实际会去调用具体对象的方法。为什么用Wrapper 而不用反射，我的理解是，wrapper内部根据方法判断执行，比起反射调用效率高。

生成Invoker对象后，由DelegateProviderMetaDataInvoker包装下，再由protocol.export(wrapperInvoker)暴露服务。这里，protocol是Protocol$Adaptive类型的,根据参数wrapperInvoker的url调用RegistryProtocol。由下面代码可知，RegistryProtocol由ProtocolListenerWrapper 和ProtocolFilterWrapper包装。

  private T createExtension(String name) {
        Class<?> clazz = getExtensionClasses().get(name);
        if (clazz == null) {
            throw findException(name);
        }
        try {
            T instance = (T) EXTENSION_INSTANCES.get(clazz);
            if (instance == null) {
                EXTENSION_INSTANCES.putIfAbsent(clazz, (T) clazz.newInstance());
                instance = (T) EXTENSION_INSTANCES.get(clazz);
            }
            injectExtension(instance);
            Set<Class<?>> wrapperClasses = cachedWrapperClasses;
            if (wrapperClasses != null && wrapperClasses.size() > 0) {
                for (Class<?> wrapperClass : wrapperClasses) {
                    instance = injectExtension((T) wrapperClass.getConstructor(type).newInstance(instance));
                }
            }
            return instance;
        } catch (Throwable t) {
            throw new IllegalStateException("Extension instance(name: " + name + ", class: " +
                    type + ")  could not be instantiated: " + t.getMessage(), t);
        }
    }

 ProtocolListenerWrapper代码比较简单，看下ProtocolFilterWrapper,

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

这个时候，由于url里面的协议是Protocol，所以走protocol.export(invoker)分支。稍后DubboProtocol时候再走下面的分支。此时invoker里面的URL如下

registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.0.0&export=dubbo%3A%2F%2F192.168.1.104%3A20880%2Fcom.alibaba.dubbo.demo.DemoService%3Fanyhost%3Dtrue%26application%3Ddemo-provider%26bind.ip%3D192.168.1.104%26bind.port%3D20880%26dubbo%3D2.0.0%26generic%3Dfalse%26interface%3Dcom.alibaba.dubbo.demo.DemoService%26methods%3DsayHello%2Cwelcome%26pid%3D26824%26side%3Dprovider%26timestamp%3D1521726309295&pid=26824&registry=zookeeper&timestamp=1521726309252

看下RegistryProtocol的代码，如下。此处是服务暴露的核心代码，一方面本地暴露，用于供外部远程调用；另一方面去注册中心注册服务。

    public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
        //export invoker
        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
        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);
        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);
                }
            }
        };
    }

先分析doLocalExport

    private <T> ExporterChangeableWrapper<T> doLocalExport(final Invoker<T> originInvoker) {
        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 InvokerDelegete<T>(originInvoker, getProviderUrl(originInvoker));
                    exporter = new ExporterChangeableWrapper<T>((Exporter<T>) protocol.export(invokerDelegete), originInvoker);
                    bounds.put(key, exporter);
                }
            }
        }
        return exporter;
    }

由于在ExtensionLoader里面RegistryProtocol生成后，设置其属性protocol时，ObjectFactory获取的属性值为Protocol$Adative，上面export方法进入DubboProtocol.export。同时，由上面的ProtocolFilterWrapper将invoker转化为调用链，

    private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
        Invoker<T> last = invoker;
        List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);
        if (filters.size() > 0) {
            for (int i = filters.size() - 1; i >= 0; i--) {
                final Filter filter = filters.get(i);
                final Invoker<T> next = last;
                last = new Invoker<T>() {

                    public Class<T> getInterface() {
                        return invoker.getInterface();
                    }

                    public URL getUrl() {
                        return invoker.getUrl();
                    }

                    public boolean isAvailable() {
                        return invoker.isAvailable();
                    }

                    public Result invoke(Invocation invocation) throws RpcException {
                        return filter.invoke(next, invocation);
                    }

                    public void destroy() {
                        invoker.destroy();
                    }

                    @Override
                    public String toString() {
                        return invoker.toString();
                    }
                };
            }
        }
        return last;
    }

由此生成的Invoke调用invoke方法时，触发第一个filter调用invoker(next,invocation)，在filter的invoker方法里面，又会触发next.invoker(invocation)，这样触发一系列的过滤器链调用，最后调用原始的invoke的invoke方法。

我们再来看DubboProtocol.export

 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);

        return exporter;
    }

上面生成的DubboExport可以理解为最终的Export，里面包含了实际调用的Invoker,这个invoke包含最初有ref生成的代理对象和一系列过滤器。生成的key如下，com.alibaba.dubbo.demo.DemoService:20880，将key 和dubboExport放入exportMap，供服务消费者查询需要的Invoker。

上面的openServer 及createServer利用netty监听消费者，看下收到消费者的请求后的处理过程。

private ExchangeHandler requestHandler = new ExchangeHandlerAdapter() {

        public Object reply(ExchangeChannel channel, Object message) throws RemotingException {
            if (message instanceof Invocation) {
                Invocation inv = (Invocation) message;
                Invoker<?> invoker = getInvoker(channel, inv);
                // need to consider backward-compatibility if it's a callback
                if (Boolean.TRUE.toString().equals(inv.getAttachments().get(IS_CALLBACK_SERVICE_INVOKE))) {
                    String methodsStr = invoker.getUrl().getParameters().get("methods");
                    boolean hasMethod = false;
                    if (methodsStr == null || methodsStr.indexOf(",") == -1) {
                        hasMethod = inv.getMethodName().equals(methodsStr);
                    } else {
                        String[] methods = methodsStr.split(",");
                        for (String method : methods) {
                            if (inv.getMethodName().equals(method)) {
                                hasMethod = true;
                                break;
                            }
                        }
                    }
                    if (!hasMethod) {
                        logger.warn(new IllegalStateException("The methodName " + inv.getMethodName() + " not found in callback service interface ,invoke will be ignored. please update the api interface. url is:" + invoker.getUrl()) + " ,invocation is :" + inv);
                        return null;
                    }
                }
                RpcContext.getContext().setRemoteAddress(channel.getRemoteAddress());
                return invoker.invoke(inv);
            }
            throw new RemotingException(channel, "Unsupported request: " + message == null ? null : (message.getClass().getName() + ": " + message) + ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress());
        }

收到请求后，先去查询invoker，

 Invoker<?> getInvoker(Channel channel, Invocation inv) throws RemotingException {
        boolean isCallBackServiceInvoke = false;
        boolean isStubServiceInvoke = false;
        int port = channel.getLocalAddress().getPort();
        String path = inv.getAttachments().get(Constants.PATH_KEY);
        // if it's callback service on client side
        isStubServiceInvoke = Boolean.TRUE.toString().equals(inv.getAttachments().get(Constants.STUB_EVENT_KEY));
        if (isStubServiceInvoke) {
            port = channel.getRemoteAddress().getPort();
        }
        //callback
        isCallBackServiceInvoke = isClientSide(channel) && !isStubServiceInvoke;
        if (isCallBackServiceInvoke) {
            path = inv.getAttachments().get(Constants.PATH_KEY) + "." + inv.getAttachments().get(Constants.CALLBACK_SERVICE_KEY);
            inv.getAttachments().put(IS_CALLBACK_SERVICE_INVOKE, Boolean.TRUE.toString());
        }
        String serviceKey = serviceKey(port, path, inv.getAttachments().get(Constants.VERSION_KEY), inv.getAttachments().get(Constants.GROUP_KEY));

        DubboExporter<?> exporter = (DubboExporter<?>) exporterMap.get(serviceKey);

        if (exporter == null)
            throw new RemotingException(channel, "Not found exported service: " + serviceKey + " in " + exporterMap.keySet() + ", may be version or group mismatch " + ", channel: consumer: " + channel.getRemoteAddress() + " --> provider: " + channel.getLocalAddress() + ", message:" + inv);

        return exporter.getInvoker();
    }

可以看到是在exporterMap里面找到DubboExporter，然后返回DubboExporterl里面的Invoker。再执行invoke方法返回。

到此本地暴露分析完毕。

本地暴露完后，获取注册中心，在注册中心注册registedProviderUrl,  dubbo://192.168.1.104:20880/com.alibaba.dubbo.demo.DemoService?anyhost=true&application=demo-provider&dubbo=2.0.0&generic=false&interface=com.alibaba.dubbo.demo.DemoService&methods=sayHello,welcome&pid=27350&side=provider&timestamp=1521729408324  这由服务消费方在注册中心订阅后获取URL，与服务提供方建立连接用的。

同时订阅overrideSubscribeUrl，会调接口是

 public synchronized void notify(List<URL> urls) {
            logger.debug("original override urls: " + urls);
            List<URL> matchedUrls = getMatchedUrls(urls, subscribeUrl);
            logger.debug("subscribe url: " + subscribeUrl + ", override urls: " + matchedUrls);
            // No matching results
            if (matchedUrls.isEmpty()) {
                return;
            }

            List<Configurator> configurators = RegistryDirectory.toConfigurators(matchedUrls);

            final Invoker<?> invoker;
            if (originInvoker instanceof InvokerDelegete) {
                invoker = ((InvokerDelegete<?>) originInvoker).getInvoker();
            } else {
                invoker = originInvoker;
            }
            //The origin invoker
            URL originUrl = RegistryProtocol.this.getProviderUrl(invoker);
            String key = getCacheKey(originInvoker);
            ExporterChangeableWrapper<?> exporter = bounds.get(key);
            if (exporter == null) {
                logger.warn(new IllegalStateException("error state, exporter should not be null"));
                return;
            }
            //The current, may have been merged many times
            URL currentUrl = exporter.getInvoker().getUrl();
            //Merged with this configuration
            URL newUrl = getConfigedInvokerUrl(configurators, originUrl);
            if (!currentUrl.equals(newUrl)) {
                RegistryProtocol.this.doChangeLocalExport(originInvoker, newUrl);
                logger.info("exported provider url changed, origin url: " + originUrl + ", old export url: " + currentUrl + ", new export url: " + newUrl);
            }
        }

大意是看配置生成的URL与exporter里面的URL是否一致，不一致重新暴露。

服务暴露分析完了。