Dubbo-服务暴露流程

 

服务提供者服务暴露过程是，当服务提供者NettyServer启动完成后，向ZK注册订阅的过程

服务消费者服务暴露过程是，创建代理对象的时候，注ZK注册订阅的过程

 

一、服务提供方

注册服务：调用register方法，ZookeeperRegistry中的doRegister方法。zk节点上生成providers节点的过程。

订阅服务：调用subscribe方法，ZookeeperRegistry中的doSubscribe方法。zk节点上生成configurators节点的过程。

public class RegistryProtocol implements Protocol {
    
    public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
        //export invoker
        // 启动NettyServer服务
        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);
        
        // 《服务提供方》向注册中心注册服务
        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);
        // 《服务提供方》订阅服务
        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);
                }
            }
        };
    }    
}

 

 

二、服务消费方

注册服务：调用register方法，ZookeeperRegistry中的doRegister方法。zk节点上生成consumers节点的过程。

订阅服务：调用subscribe方法，ZookeeperRegistry中的doSubscribe方法。zk节点上生成routers节点的过程。

 

 

我们知道消费者在创建代理bean的时候（即调用createProxy方法时），需要得到一个调用者invoker对象。

private transient volatile Invoker<?> invoker;

private T createProxy(Map<String, String> map) {
    // 省略若干代码...
    if (isJvmRefer) {
        URL url = new URL(Constants.LOCAL_PROTOCOL, NetUtils.LOCALHOST, 0, interfaceClass.getName()).addParameters(map);
        // 核心方法，拿到invoker对象        
        invoker = refprotocol.refer(interfaceClass, url);
    } else {
        // 省略若干代码...
        if (urls.size() == 1) {
            // 核心方法，拿到invoker对象
            // refprotocol为Protocol$Adpative对象
            invoker = refprotocol.refer(interfaceClass, urls.get(0));
        } else {
            // 省略若干代码...
        }
    }
    // 核心方法create service proxy 
    // 将下面这段代码替换成 ProxyFactory$Adaptive 中 getProxy中的部分
    return (T) proxyFactory.getProxy(invoker); 
}

调用RegistryProtocol中的refer方法

    public <T> Invoker<T> refer(Class<T> type, URL url) throws RpcException {
        url = url.setProtocol(url.getParameter(Constants.REGISTRY_KEY, Constants.DEFAULT_REGISTRY)).removeParameter(Constants.REGISTRY_KEY);
        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(Constants.REFER_KEY));
        String group = qs.get(Constants.GROUP_KEY);
        if (group != null && group.length() > 0) {
            if ((Constants.COMMA_SPLIT_PATTERN.split(group)).length > 1
                    || "*".equals(group)) {
                return doRefer(getMergeableCluster(), registry, type, url);
            }
        }
        return doRefer(cluster, registry, type, url);
    }

    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.getUrl().getParameters());
        URL subscribeUrl = new URL(Constants.CONSUMER_PROTOCOL, parameters.remove(Constants.REGISTER_IP_KEY), 0, type.getName(), parameters);
        if (!Constants.ANY_VALUE.equals(url.getServiceInterface())
                && url.getParameter(Constants.REGISTER_KEY, true)) {
            // 《服务消费方》注册服务
            registry.register(subscribeUrl.addParameters(Constants.CATEGORY_KEY, Constants.CONSUMERS_CATEGORY,
                    Constants.CHECK_KEY, String.valueOf(false)));
        }
        // 《服务消费方》订阅服务
        directory.subscribe(subscribeUrl.addParameter(Constants.CATEGORY_KEY,
                Constants.PROVIDERS_CATEGORY
                        + "," + Constants.CONFIGURATORS_CATEGORY
                        + "," + Constants.ROUTERS_CATEGORY));

        Invoker invoker = cluster.join(directory);
        ProviderConsumerRegTable.registerConsuemr(invoker, url, subscribeUrl, directory);
        return invoker;
    }