dubbo的启动过程（四）--服务方暴露

doExport

各个配置信息、配置中心准备好了，开始服务暴露的过程

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

private void doExportUrls() {
    // 把application、config、path、protocol、运行参数等拼接到URL中
    List<URL> registryURLs = loadRegistries(true);
    // 每个协议都暴露
    for (ProtocolConfig protocolConfig : protocols) {
        // 拼接path、group、version
        String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
        // 创建providerModel，构造方法里有个init方法，会把方法存入到method中
        ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
        // 存入到PROVIDED_SERVICES中
        ApplicationModel.initProviderModel(pathKey, providerModel);
        doExportUrlsFor1Protocol(protocolConfig, registryURLs);
    }
}

doExportUrlsFor1Protocol

private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
    
    String name = protocolConfig.getName();
    if (StringUtils.isEmpty(name)) {
        name = DUBBO;
    }
    // 把各个信息放入map中
    Map<String, String> map = new HashMap<String, String>();
    map.put(SIDE_KEY, PROVIDER_SIDE);

    appendRuntimeParameters(map);
    appendParameters(map, metrics);
    appendParameters(map, application);
    appendParameters(map, module);
    // remove 'default.' prefix for configs from ProviderConfig
    // appendParameters(map, provider, Constants.DEFAULT_KEY);
    appendParameters(map, provider);
    appendParameters(map, protocolConfig);
    appendParameters(map, this);
    // 如果有设置methods，则设置方法的各自参数
    if (CollectionUtils.isNotEmpty(methods)) {
        for (MethodConfig method : methods) {
            appendParameters(map, method, method.getName());
            String retryKey = method.getName() + ".retry";
            if (map.containsKey(retryKey)) {
                String retryValue = map.remove(retryKey);
                if (Boolean.FALSE.toString().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 != null && 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())) {
                                            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())) {
                                                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) {
                        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
    }
    //设置泛化、版本、method
    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)), ","));
        }
    }
    // 设置token
    if (!ConfigUtils.isEmpty(token)) {
        if (ConfigUtils.isDefault(token)) {
            map.put(TOKEN_KEY, UUID.randomUUID().toString());
        } else {
            map.put(TOKEN_KEY, token);
        }
    }
    // export service
    // 获取ip，如果没有设置则默认本机
    String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
    // 获取端口，没有设置则为20880
    Integer port = this.findConfigedPorts(protocolConfig, name, map);
    // 拼接暴露的URL
    URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);
    // 如果已经扩展了协议，则配置信息
    if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
            .hasExtension(url.getProtocol())) {
        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)) {
            // 暴露本地服务
            exportLocal(url);
        }
        // export to remote if the config is not local (export to local only when config is local)
        // 暴露远程服务
        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));
                    // 监听
                    URL monitorUrl = loadMonitor(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);
                    }
                    // 暴露服务
                    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);
                // 这个protocol是RegistryProtocol，看下面的暴露远程服务
                Exporter<?> exporter = protocol.export(wrapperInvoker);
                exporters.add(exporter);
            }
            /**
             * @since 2.7.0
             * ServiceData Store
             */
            MetadataReportService metadataReportService = null;
            if ((metadataReportService = getMetadataReportService()) != null) {
                metadataReportService.publishProvider(url);
            }
        }
    }
    this.urls.add(url);
}

exportLocal：本地暴露

在SPI#createExtension中，我们看到了Extension的创建，是wrapperClass装饰的，而InjvmProtocol是由org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper、org.apache.dubbo.qos.protocol.QosProtocolWrapper、org.apache.dubbo.rpc.protocol.ProtocolListenerWrapper这三个装饰的。调用的时候，会先调用ProtocolListenerWrapper的export方法，然后会调用QosProtocolWrapper的export方法，然后是ProtocolFilterWrapper的export方法，这里会获取filter，最后是InjvmProtocol的InjvmProtocol。从InjvmProtocol到ProtocolFilterWrapper到QosProtocolWrapper的export方法，都执行完后，就开始创建一个ListenerExporterWrapper，负责监听export和unexport。

private void exportLocal(URL url) {
    URL local = URLBuilder.from(url)
            .setProtocol(LOCAL_PROTOCOL)
            .setHost(LOCALHOST_VALUE)
            .setPort(0)
            .build();
    // PROXY_FACTORY.getInvoker是包装实现类的信息
    // local是injvm:开头的，所以这个protocol是InjvmProtocol 
    Exporter<?> exporter = protocol.export(
            PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, local));
    // 添加到exporters
    exporters.add(exporter);
    logger.info("Export dubbo service " + interfaceClass.getName() + " to local registry url : " + local);
}

// ProtocolListenerWrapper
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
    if (REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
        return protocol.export(invoker);
    }
    
    return new ListenerExporterWrapper<T>(protocol.export(invoker),
            Collections.unmodifiableList(ExtensionLoader.getExtensionLoader(ExporterListener.class)
                    .getActivateExtension(invoker.getUrl(), EXPORTER_LISTENER_KEY)));
}

// QosProtocolWrapper
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
    if (REGISTRY_PROTOCOL.equals(invoker.getUrl().getProtocol())) {
        startQosServer(invoker.getUrl());
        return protocol.export(invoker);
    }
    return protocol.export(invoker);
}

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

// InjvmProtocol
public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
    return new InjvmExporter<T>(invoker, invoker.getUrl().getServiceKey(), exporterMap);
}

暴露远程服务

通过netty开启服务，并把信息注册到注册中心

RegistryProtocol的export

//RegistryProtocol
public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
    // 获取注册中心的地址
    URL registryUrl = getRegistryUrl(originInvoker);
    // url to export locally
    // 获取服务方地址
    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.
    // 订阅覆盖的地址
    final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
    // 监听
    final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
    overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);

    providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
    //export invoker
    // 这里会调用DubboProtocol的export方法
    final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);

    // url to registry
    // 创建一个registry
    final Registry registry = getRegistry(originInvoker);
    // 获取已经注册的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 = providerUrl.getParameter(REGISTER_KEY, true);
    if (register) {
        register(registryUrl, registeredProviderUrl);
        // 设置为已注册
        providerInvokerWrapper.setReg(true);
    }

    // Deprecated! Subscribe to override rules in 2.6.x or before.
    // 订阅
    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);
}

DubboProtocol的export

public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
    // 获取地址
    URL url = invoker.getUrl();

    // export service.
    //获取服务
    String key = serviceKey(url);
    DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
    exporterMap.put(key, exporter);

    //export an stub service for dispatching event
    // 是否为调度事件暴露stub服务
    Boolean isStubSupportEvent = url.getParameter(STUB_EVENT_KEY, DEFAULT_STUB_EVENT);
    Boolean isCallbackservice = url.getParameter(IS_CALLBACK_SERVICE, false);
    if (isStubSupportEvent && !isCallbackservice) {
        String stubServiceMethods = url.getParameter(STUB_EVENT_METHODS_KEY);
        if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
            if (logger.isWarnEnabled()) {
                logger.warn(new IllegalStateException("consumer [" + url.getParameter(INTERFACE_KEY) +
                        "], has set stubproxy support event ,but no stub methods founded."));
            }

        } else {
            stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
        }
    }
    // 开启服务
    openServer(url);
    // 实现了SerializationOptimizer接口的先实例化
    optimizeSerialization(url);

    return exporter;
}

openServer

private void openServer(URL url) {
    // find server.
    // 获取服务地址
    String key = url.getAddress();
    //client can export a service which's only for server to invoke
    boolean isServer = url.getParameter(IS_SERVER_KEY, true);
    if (isServer) {
        // ExchangeServer如果为空，则创建一个
        ExchangeServer server = serverMap.get(key);
        if (server == null) {
            synchronized (this) {
                server = serverMap.get(key);
                if (server == null) {
                    // Exchangers的Transporters的bind里，通过netty绑定开启服务
                    serverMap.put(key, createServer(url));
                }
            }
        } else {
            // server supports reset, use together with override
            server.reset(url);
        }
    }
}