Dubbo服务消费过程

服务消费者端代码

@DubboReference(version = "1.0.0")
private DemoService demoService;

public static void main(String[] args) {
    SpringApplication.run(DubboAutoConfigurationConsumerBootstrap.class).close();
}
@Bean
public ApplicationRunner runner() {
    return new ApplicationRunner() {
        public void run(ApplicationArguments args) throws Exception {
            System.out.println(demoService.sayHello("mercyblitz"));
        }
    };
}

我们再次来到 DubboComponentScanRegistrar 中、

@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {

    Set<String> packagesToScan = getPackagesToScan(importingClassMetadata);

    registerServiceAnnotationBeanPostProcessor(packagesToScan, registry);

    // @since 2.7.6 Register the common beans
    registerCommonBeans(registry);
}
static void registerCommonBeans(BeanDefinitionRegistry registry) {

  // Since 2.5.7 Register @Reference Annotation Bean Processor as an infrastructure Bean
  registerInfrastructureBean(registry, ReferenceAnnotationBeanPostProcessor.BEAN_NAME,
  ReferenceAnnotationBeanPostProcessor.class);

  // Since 2.7.4 [Feature] https://github.com/apache/dubbo/issues/5093
  registerInfrastructureBean(registry, DubboConfigAliasPostProcessor.BEAN_NAME,
  DubboConfigAliasPostProcessor.class);

  // Since 2.7.5 Register DubboLifecycleComponentApplicationListener as an infrastructure Bean
  registerInfrastructureBean(registry, DubboLifecycleComponentApplicationListener.BEAN_NAME,
  DubboLifecycleComponentApplicationListener.class);

  // Since 2.7.4 Register DubboBootstrapApplicationListener as an infrastructure Bean
  registerInfrastructureBean(registry, DubboBootstrapApplicationListener.BEAN_NAME,
  DubboBootstrapApplicationListener.class);

  // Since 2.7.6 Register DubboConfigDefaultPropertyValueBeanPostProcessor as an infrastructure Bean
  registerInfrastructureBean(registry, DubboConfigDefaultPropertyValueBeanPostProcessor.BEAN_NAME,
  DubboConfigDefaultPropertyValueBeanPostProcessor.class);
}

我们看到了 ReferenceAnnotationBeanPostProcessor、该类同时也实现了 InstantiationAwareBeanPostProcessor 接口。

该方法会在 Spring 填充属性的时候被调用、通过该方法返回注入的对象

@Override
protected Object doGetInjectedBean(AnnotationAttributes attributes, Object bean, String beanName, Class<?> injectedType,
                                   InjectionMetadata.InjectedElement injectedElement) throws Exception {
    /**
     * The name of bean that annotated Dubbo's {@link Service @Service} in local Spring {@link ApplicationContext}
     */
    String referencedBeanName = buildReferencedBeanName(attributes, injectedType);

    /**
     * The name of bean that is declared by {@link Reference @Reference} annotation injection
     */
    String referenceBeanName = getReferenceBeanName(attributes, injectedType);

    ReferenceBean referenceBean = buildReferenceBeanIfAbsent(referenceBeanName, attributes, injectedType);

    boolean localServiceBean = isLocalServiceBean(referencedBeanName, referenceBean, attributes);

    prepareReferenceBean(referencedBeanName, referenceBean, localServiceBean);

    registerReferenceBean(referencedBeanName, referenceBean, attributes, localServiceBean, injectedType);

    cacheInjectedReferenceBean(referenceBean, injectedElement);

    return referenceBean.get();
}

我们可以看到 最终调用 ReferenceBean 的 get 方法

public synchronized T get() {
    if (destroyed) {
        throw new IllegalStateException("The invoker of ReferenceConfig(" + url + ") has already destroyed!");
    }
    if (ref == null) {
        init();
    }
    return ref;
}

ref 此时为 null 进入到 init 方法中

public synchronized void init() {
        .......
				// 构造参数 map
        ref = createProxy(map);
				.......
    }
private T createProxy(Map<String, String> map) {
        if (shouldJvmRefer(map)) {
					........
        } else {
            urls.clear();
            if (url != null && url.length() > 0) { // user specified URL, could be peer-to-peer address, or register center's address.
              ......//点对点通信
            } else { // assemble URL from register center's configuration
                // if protocols not injvm checkRegistry
                if (!LOCAL_PROTOCOL.equalsIgnoreCase(getProtocol())) {
                    checkRegistry();
                    List<URL> us = ConfigValidationUtils.loadRegistries(this, false);
                    if (CollectionUtils.isNotEmpty(us)) {
                        for (URL u : us) {
                            URL monitorUrl = ConfigValidationUtils.loadMonitor(this, u);
                            if (monitorUrl != null) {
                                map.put(MONITOR_KEY, URL.encode(monitorUrl.toFullString()));
                            }
                            urls.add(u.addParameterAndEncoded(REFER_KEY, StringUtils.toQueryString(map)));
                        }
                    }
                    if (urls.isEmpty()) {
                        throw new IllegalStateException("No such any registry to reference " + interfaceName + " on the consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", please config <dubbo:registry address=\"...\" /> to your spring config.");
                    }
                }
            }
					// 单个注册中心
            if (urls.size() == 1) {
                invoker = REF_PROTOCOL.refer(interfaceClass, urls.get(0));
            } else {
              // 多个注册中心
                List<Invoker<?>> invokers = new ArrayList<Invoker<?>>();
                URL registryURL = null;
                for (URL url : urls) {
                    invokers.add(REF_PROTOCOL.refer(interfaceClass, url));
                    if (UrlUtils.isRegistry(url)) {
                        registryURL = url; // use last registry url
                    }
                }
                if (registryURL != null) { // registry url is available
                    // for multi-subscription scenario, use 'zone-aware' policy by default
                    URL u = registryURL.addParameterIfAbsent(CLUSTER_KEY, ZoneAwareCluster.NAME);
                    // The invoker wrap relation would be like: ZoneAwareClusterInvoker(StaticDirectory) -> FailoverClusterInvoker(RegistryDirectory, routing happens here) -> Invoker
                    invoker = CLUSTER.join(new StaticDirectory(u, invokers));
                } else { // not a registry url, must be direct invoke.
                    invoker = CLUSTER.join(new StaticDirectory(invokers));
                }
            }
        }

				.........
        // create service proxy
        return (T) PROXY_FACTORY.getProxy(invoker, ProtocolUtils.isGeneric(generic));
    }

无论配置了单个注册中心、还是多个、都需要从注册中心中获取服务提供者的地址

REF_PROTOCOL.refer(interfaceClass, url)

RegistryProtocol

@Override
@SuppressWarnings("unchecked")
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
    url = getRegistryUrl(url);
    Registry registry = registryFactory.getRegistry(url);
    if (RegistryService.class.equals(type)) {
        return proxyFactory.getInvoker((T) registry, type, url);
    }

    // group="a,b" or group="*"
    Map<String, String> qs = StringUtils.parseQueryString(url.getParameterAndDecoded(REFER_KEY));
    String group = qs.get(GROUP_KEY);
    if (group != null && group.length() > 0) {
        if ((COMMA_SPLIT_PATTERN.split(group)).length > 1 || "*".equals(group)) {
            return doRefer(getMergeableCluster(), registry, type, url);
        }
    }
    return doRefer(cluster, registry, type, url);
}

直接进入到 doRefer 中干实事

private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
    RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
    directory.setRegistry(registry);
    directory.setProtocol(protocol);
    // all attributes of REFER_KEY
    Map<String, String> parameters = new HashMap<String, String>(directory.getConsumerUrl().getParameters());
    URL subscribeUrl = new URL(CONSUMER_PROTOCOL, parameters.remove(REGISTER_IP_KEY), 0, type.getName(), parameters);
    if (directory.isShouldRegister()) {
        directory.setRegisteredConsumerUrl(subscribeUrl);
        registry.register(directory.getRegisteredConsumerUrl());
    }
    directory.buildRouterChain(subscribeUrl);
    directory.subscribe(toSubscribeUrl(subscribeUrl));

    Invoker<T> invoker = cluster.join(directory);
    List<RegistryProtocolListener> listeners = findRegistryProtocolListeners(url);
    if (CollectionUtils.isEmpty(listeners)) {
        return invoker;
    }

    RegistryInvokerWrapper<T> registryInvokerWrapper = new RegistryInvokerWrapper<>(directory, cluster, invoker, subscribeUrl);
    for (RegistryProtocolListener listener : listeners) {
        listener.onRefer(this, registryInvokerWrapper);
    }
    return registryInvokerWrapper;
}

进入到订阅服务注册中心的路径、会在此处获取到服务提供者的真实地址

public void subscribe(URL url) {
    setConsumerUrl(url);
    CONSUMER_CONFIGURATION_LISTENER.addNotifyListener(this);
    serviceConfigurationListener = new ReferenceConfigurationListener(this, url);
    registry.subscribe(url, this);
}

url 的地址如下。

consumer://192.168.1.103/com.demo.api.DemoService?application=dubbo-auto-configure-consumer-sample&category=providers,configurators,routers&dubbo=2.0.2&init=false&interface=com.demo.api.DemoService&metadata-type=remote&methods=sayHello&pid=85321&qos.enable=false&release=2.7.8&revision=1.0.0&side=consumer&sticky=false&timestamp=1645947096408&version=1.0.0

订阅了 providers,configurators,routers 这三个目录

进入到 ZookeeperRegistry

@Override
public void doSubscribe(final URL url, final NotifyListener listener) {
    try {
        if (ANY_VALUE.equals(url.getServiceInterface())) {
					......
        } else {
            List<URL> urls = new ArrayList<>();
            for (String path : toCategoriesPath(url)) {
                ConcurrentMap<NotifyListener, ChildListener> listeners = zkListeners.computeIfAbsent(url, k -> new ConcurrentHashMap<>());
                ChildListener zkListener = listeners.computeIfAbsent(listener, k -> (parentPath, currentChilds) -> ZookeeperRegistry.this.notify(url, k, toUrlsWithEmpty(url, parentPath, currentChilds)));
                zkClient.create(path, false);
                List<String> children = zkClient.addChildListener(path, zkListener);
                if (children != null) {
                    urls.addAll(toUrlsWithEmpty(url, path, children));
                }
            }
            notify(url, listener, urls);
        }
    } catch (Throwable e) {
        throw new RpcException("Failed to subscribe " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
    }
}

path 分别为

/dubbo/com.demo.api.DemoService/providers

/dubbo/com.demo.api.DemoService/configurators

/dubbo/com.demo.api.DemoService/routers

providers 获取到到值

dubbo%3A%2F%2F127.0.0.1%3A12345%2Fcom.demo.api.DemoService%3Fanyhost%3Dtrue%26application%3Ddubbo-auto-configuration-provider-demo%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26interface%3Dcom.demo.api.DemoService%26methods%3DsayHello%26pid%3D85689%26release%3D2.7.7%26revision%3D1.0.0%26side%3Dprovider%26timestamp%3D1645947588375%26version%3D1.0.0

@Override
protected void notify(URL url, NotifyListener listener, List<URL> urls) {
		.......
    doNotify(url, listener, urls);
}
protected void doNotify(URL url, NotifyListener listener, List<URL> urls) {
	super.notify(url, listener, urls);
}
protected void notify(URL url, NotifyListener listener, List<URL> urls) {
	.......
  Map<String, List<URL>> result = new HashMap<>();
  for (URL u : urls) {
    if (UrlUtils.isMatch(url, u)) {
      String category = u.getParameter(CATEGORY_KEY, DEFAULT_CATEGORY);
      List<URL> categoryList = result.computeIfAbsent(category, k -> new ArrayList<>());
      categoryList.add(u);
    }
  }

  Map<String, List<URL>> categoryNotified = notified.computeIfAbsent(url, u -> new ConcurrentHashMap<>());
  for (Map.Entry<String, List<URL>> entry : result.entrySet()) {
    String category = entry.getKey();
    List<URL> categoryList = entry.getValue();
    categoryNotified.put(category, categoryList);
    listener.notify(categoryList);
    saveProperties(url);
  }
}

listener.notify(categoryList);

这里的 listener 就是我们一开始的 DiretoryRegistry

@Override
public synchronized void notify(List<URL> urls) {
    Map<String, List<URL>> categoryUrls = urls.stream()
            .filter(Objects::nonNull)
            .filter(this::isValidCategory)
            .filter(this::isNotCompatibleFor26x)
            .collect(Collectors.groupingBy(this::judgeCategory));

    List<URL> configuratorURLs = categoryUrls.getOrDefault(CONFIGURATORS_CATEGORY, Collections.emptyList());
    this.configurators = Configurator.toConfigurators(configuratorURLs).orElse(this.configurators);

    List<URL> routerURLs = categoryUrls.getOrDefault(ROUTERS_CATEGORY, Collections.emptyList());
    toRouters(routerURLs).ifPresent(this::addRouters);

    // providers
    List<URL> providerURLs = categoryUrls.getOrDefault(PROVIDERS_CATEGORY, Collections.emptyList());
    /**
     * 3.x added for extend URL address
     */
    ExtensionLoader<AddressListener> addressListenerExtensionLoader = ExtensionLoader.getExtensionLoader(AddressListener.class);
    List<AddressListener> supportedListeners = addressListenerExtensionLoader.getActivateExtension(getUrl(), (String[]) null);
    if (supportedListeners != null && !supportedListeners.isEmpty()) {
        for (AddressListener addressListener : supportedListeners) {
            providerURLs = addressListener.notify(providerURLs, getConsumerUrl(),this);
        }
    }
    refreshOverrideAndInvoker(providerURLs);
}

进入到 refreshOverrideAndInvoker 中

private void refreshOverrideAndInvoker(List<URL> urls) {
    // mock zookeeper://xxx?mock=return null
    overrideDirectoryUrl();
    refreshInvoker(urls);
}

private void refreshInvoker(List<URL> invokerUrls) {
    Assert.notNull(invokerUrls, "invokerUrls should not be null");

    if (invokerUrls.size() == 1
            && invokerUrls.get(0) != null
            && EMPTY_PROTOCOL.equals(invokerUrls.get(0).getProtocol())) {
			.......
    } else {
			......
        Map<String, Invoker<T>> newUrlInvokerMap = toInvokers(invokerUrls);// Translate url list to Invoker map
        if (CollectionUtils.isEmptyMap(newUrlInvokerMap)) {
            logger.error(new IllegalStateException("urls to invokers error .invokerUrls.size :" + invokerUrls.size() + ", invoker.size :0. urls :" + invokerUrls
                    .toString()));
            return;
        }

        List<Invoker<T>> newInvokers = Collections.unmodifiableList(new ArrayList<>(newUrlInvokerMap.values()));
        routerChain.setInvokers(newInvokers);
        this.invokers = multiGroup ? toMergeInvokerList(newInvokers) : newInvokers;
        this.urlInvokerMap = newUrlInvokerMap;

        try {
            destroyUnusedInvokers(oldUrlInvokerMap, newUrlInvokerMap); // Close the unused Invoker
        } catch (Exception e) {
            logger.warn("destroyUnusedInvokers error. ", e);
        }
    }
}

toInvokers(invokerUrls)

将 url 转化成 Invoker

private Map<String, Invoker<T>> toInvokers(List<URL> urls) {
    Map<String, Invoker<T>> newUrlInvokerMap = new HashMap<>();
    if (urls == null || urls.isEmpty()) {
        return newUrlInvokerMap;
    }
    Set<String> keys = new HashSet<>();
    String queryProtocols = this.queryMap.get(PROTOCOL_KEY);
    for (URL providerUrl : urls) {
        // If protocol is configured at the reference side, only the matching protocol is selected
        ............
        if (EMPTY_PROTOCOL.equals(providerUrl.getProtocol())) {
            continue;
        }
        if (!ExtensionLoader.getExtensionLoader(Protocol.class).hasExtension(providerUrl.getProtocol())) {
           ........
            continue;
        }
        URL url = mergeUrl(providerUrl);

        String key = url.toFullString(); // The parameter urls are sorted
        if (keys.contains(key)) { // Repeated url
            continue;
        }
        keys.add(key);
        // Cache key is url that does not merge with consumer side parameters, regardless of how the consumer combines parameters, if the server url changes, then refer again
        Map<String, Invoker<T>> localUrlInvokerMap = this.urlInvokerMap; // local reference
        Invoker<T> invoker = localUrlInvokerMap == null ? null : localUrlInvokerMap.get(key);
        if (invoker == null) { // Not in the cache, refer again
            try {
                boolean enabled = true;
                if (url.hasParameter(DISABLED_KEY)) {
                    enabled = !url.getParameter(DISABLED_KEY, false);
                } else {
                    enabled = url.getParameter(ENABLED_KEY, true);
                }
                if (enabled) {
                    invoker = new InvokerDelegate<>(protocol.refer(serviceType, url), url, providerUrl);
                }
            } catch (Throwable t) {
                logger.error("Failed to refer invoker for interface:" + serviceType + ",url:(" + url + ")" + t.getMessage(), t);
            }
            if (invoker != null) { // Put new invoker in cache
                newUrlInvokerMap.put(key, invoker);
            }
        } else {
            newUrlInvokerMap.put(key, invoker);
        }
    }
    keys.clear();
    return newUrlInvokerMap;
}

根据协议调用 refer 方法

invoker = new InvokerDelegate<>(protocol.refer(serviceType, url), url, providerUrl);

ProtocolFilterWrapper 这里也会创建一系列的 Filter、在调用真正的 Invoker 之前执行

@Override
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
    if (UrlUtils.isRegistry(url)) {
        return protocol.refer(type, url);
    }
    return buildInvokerChain(protocol.refer(type, url), REFERENCE_FILTER_KEY, CommonConstants.CONSUMER);
}

AbstractProtocol 异步转同步

@Override
public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
    return new AsyncToSyncInvoker<>(protocolBindingRefer(type, url));
}

DubboProtocol 这里直接返回一个 DubboInvoker

@Override
public <T> Invoker<T> protocolBindingRefer(Class<T> serviceType, URL url) throws RpcException {
    optimizeSerialization(url);

    // create rpc invoker.
    DubboInvoker<T> invoker = new DubboInvoker<T>(serviceType, url, getClients(url), invokers);
    invokers.add(invoker);

    return invoker;
}

getClients 则会去与服务提供者建立连接

private ExchangeClient[] getClients(URL url) {
    boolean useShareConnect = false;

    int connections = url.getParameter(CONNECTIONS_KEY, 0);
    List<ReferenceCountExchangeClient> shareClients = null;
    if (connections == 0) {
        useShareConnect = true;
        String shareConnectionsStr = url.getParameter(SHARE_CONNECTIONS_KEY, (String) null);
        connections = Integer.parseInt(StringUtils.isBlank(shareConnectionsStr) ? ConfigUtils.getProperty(SHARE_CONNECTIONS_KEY,
                DEFAULT_SHARE_CONNECTIONS) : shareConnectionsStr);
        shareClients = getSharedClient(url, connections);
    }

    ExchangeClient[] clients = new ExchangeClient[connections];
    for (int i = 0; i < clients.length; i++) {
        if (useShareConnect) {
            clients[i] = shareClients.get(i);

        } else {
            clients[i] = initClient(url);
        }
    }

    return clients;
}

我们现在回到 RegistryProtocol 中 directory.subscribe(toSubscribeUrl(subscribeUrl)); 的流程上面我们已经讲了

private <T> Invoker<T> doRefer(Cluster cluster, Registry registry, Class<T> type, URL url) {
    RegistryDirectory<T> directory = new RegistryDirectory<T>(type, url);
    directory.setRegistry(registry);
    directory.setProtocol(protocol);
    // all attributes of REFER_KEY
    Map<String, String> parameters = new HashMap<String, String>(directory.getConsumerUrl().getParameters());
    URL subscribeUrl = new URL(CONSUMER_PROTOCOL, parameters.remove(REGISTER_IP_KEY), 0, type.getName(), parameters);
    if (directory.isShouldRegister()) {
        directory.setRegisteredConsumerUrl(subscribeUrl);
        registry.register(directory.getRegisteredConsumerUrl());
    }
    directory.buildRouterChain(subscribeUrl);
    directory.subscribe(toSubscribeUrl(subscribeUrl));

    Invoker<T> invoker = cluster.join(directory);
    List<RegistryProtocolListener> listeners = findRegistryProtocolListeners(url);
    if (CollectionUtils.isEmpty(listeners)) {
        return invoker;
    }

    RegistryInvokerWrapper<T> registryInvokerWrapper = new RegistryInvokerWrapper<>(directory, cluster, invoker, subscribeUrl);
    for (RegistryProtocolListener listener : listeners) {
        listener.onRefer(this, registryInvokerWrapper);
    }
    return registryInvokerWrapper;

Invoker<T> invoker = cluster.join(directory); 下面进入到这个方法中

MockClusterWrapper 就是我们常用的 mock 功能

@Override
public <T> Invoker<T> join(Directory<T> directory) throws RpcException {
    return new MockClusterInvoker<T>(directory,
            this.cluster.join(directory));
}

AbstractCluster 则会创建一系列的 Interceptor 、在真正调用 Invoker 之前执行

@Override
public <T> Invoker<T> join(Directory<T> directory) throws RpcException {
    return buildClusterInterceptors(doJoin(directory), directory.getUrl().getParameter(REFERENCE_INTERCEPTOR_KEY));
}

FailoverCluster 我们默认是 Failover 策略

@Override
public <T> AbstractClusterInvoker<T> doJoin(Directory<T> directory) throws RpcException {
    return new FailoverClusterInvoker<>(directory);
}

再回到我们的 org.apache.dubbo.config.ReferenceConfig#createProxy 中、如果是多个注册中心、则会再 join 一次、因为也要对不同的注册中心进行选择对应的服务提供者。多一层负载均衡

在 org.apache.dubbo.config.ReferenceConfig#createProxy 最后

return (T) PROXY_FACTORY.getProxy(invoker, ProtocolUtils.isGeneric(generic));

通过代理工厂创建一个代理 JavassistProxyFactory

@SuppressWarnings("unchecked")
public <T> T getProxy(Invoker<T> invoker, Class<?>[] interfaces) {
    return (T) Proxy.getProxy(interfaces).newInstance(new InvokerInvocationHandler(invoker));
}

至于真正发起调用的逻辑、我们放到下一个文章去写