搞懂Dubbo服务发布与服务注册

一.前言

　　本文讲服务发布与服务注册，服务提供者本地发布服务，然后向注册中心注册服务，将服务实现类以服务接口的形式提供出去，以便服务消费者从注册中心查阅并调用服务。

　　本文源码分析基于org.apache.dubbo:dubbo:2.7.2，服务端代码例子是上文的例子

　　如果没有Dubbo SPI的基础知识，建议先看Dubbo SPI，否则源码怎么跳转的将毫无头绪

　　Dubbo SPI：https://www.cnblogs.com/GrimMjx/p/10970643.html

 

二.服务发布

调用顺序

　　首先讲一下大致的服务发布的调用顺序图，蓝色方法不分析，主要是起一个netty服务

-org.apache.dubbo.config.spring.ServiceBean#onApplicationEvent
　　-org.apache.dubbo.config.ServiceConfig#export
　　　　-org.apache.dubbo.config.ServiceConfig#doExport
　　　　　　-org.apache.dubbo.config.ServiceConfig#doExportUrls
　　　　　　　　-org.apache.dubbo.config.ServiceConfig#doExportUrlsFor1Protocol
　　　　　　　　　　-org.apache.dubbo.rpc.proxy.javassist.JavassistProxyFactory#getInvoker
　　　　　　　　　　　　-org.apache.dubbo.registry.integration.RegistryProtocol#export
　　　　　　　　　　　　　　-org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol#export
　　　　　　　　　　　　　　　　-org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol#createServer
　　　　　　　　　　　　　　　　　　-org.apache.dubbo.remoting.exchange.Exchangers#bind(org.apache.dubbo.common.URL, org.apache.dubbo.remoting.exchange.ExchangeHandler)
　　　　　　　　　　　　　　　　　　　　-org.apache.dubbo.remoting.exchange.support.header.HeaderExchanger#bind
　　　　　　　　　　　　　　　　　　　　　　-org.apache.dubbo.remoting.Transporters#bind(org.apache.dubbo.common.URL, org.apache.dubbo.remoting.ChannelHandler...)
　　　　　　　　　　　　　　　　　　　　　　　　-org.apache.dubbo.remoting.transport.netty.NettyTransporter#bind

　　　　　　　　　　　　　　　　　　　　　　　　　　...

源码分析

1.org.apache.dubbo.config.spring.ServiceBean#onApplicationEvent，这个方法就不多说了，注释写的很详细了

/**
 * ServiceBean实现了ApplicationListener接口
 * 在IOC的容器的启动过程，当所有的bean都已经处理完成之后，spring ioc容器会发布ContextRefreshedEvent事件。
 * 此处就是接收到事件处理的逻辑，开始服务发布之旅
 *
 * @param event
 */
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
    // 是否已发布  &&  是否已经被取消发布
    if (!isExported() && !isUnexported()) {
        if (logger.isInfoEnabled()) {
            logger.info("The service ready on spring started. service: " + getInterface());
        }
        // 发布
        export();
    }
}

2.org.apache.dubbo.config.ServiceConfig#export，这里的checkAndUpdateSubConfigs主要做的就是检测标签合法，检测各种对象是否为空，为空则创建。之后判断是否可以发布和是否需要延迟发布，需要则延迟再doExport

public synchronized void export() {
    // 检测<dubbo:service>的interface是否合法
    // 检查provider为空
    // 检查各种对象是否为空，为空则创建
    checkAndUpdateSubConfigs();
    if (!shouldExport()) {
        return;
    }
    // 是否延迟？
    if (shouldDelay()) {
        // 延迟
        DELAY_EXPORT_EXECUTOR.schedule(this::doExport, getDelay(), TimeUnit.MILLISECONDS);
    } else {
        doExport();
    }
}

3.org.apache.dubbo.config.ServiceConfig#doExport，注释写的很清楚，还是没有走到核心逻辑

protected synchronized void doExport() {
    // 是否已经被取消发布
    if (unexported) {
        throw new IllegalStateException("The service " + interfaceClass.getName() + " has already unexported!");
    }
    // 是否已经发布，注意这个变量volatile修饰
    if (exported) {
        return;
    }
    exported = true;
    if (StringUtils.isEmpty(path)) {
        path = interfaceName;
    }
    doExportUrls();
}

4.org.apache.dubbo.config.ServiceConfig#doExportUrls，先加载要注册的url，然后遍历所有协议，发布服务并注册

@SuppressWarnings({"unchecked", "rawtypes"})
private void doExportUrls() {
    // 加载要注册的url
    // registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=dubbo-server&dubbo=2.5.3&pid=10516&registry=zookeeper&timestamp=1559889491339
    List<URL> registryURLs = loadRegistries(true);
    // for循环每个协议，发布服务并注册到注册中心
    for (ProtocolConfig protocolConfig : protocols) {
        String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
        ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
        ApplicationModel.initProviderModel(pathKey, providerModel);
        doExportUrlsFor1Protocol(protocolConfig, registryURLs);
    }
}

5.org.apache.dubbo.config.ServiceConfig#doExportUrlsFor1Protocol，看方法名字也知道，单一协议多导出服务。这个方法做的事情比较多，我这边拆成4个部分，第一部分、第二部分和第三部分都是在做填充map的事情，第三部分最后生成导出url。第四部分开始发布服务，里面会判断到底是发布服务并且注册到注册中心呢还是仅发布服务。

private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
    /** 第一部分开始 **/
    String name = protocolConfig.getName();
    // 为空或者为空字符串，默认dubbo协议
    if (StringUtils.isEmpty(name)) {
        name = DUBBO;
    }

    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);
    // 上面的代码就是将版本，方法，各种配置放到map里去
    // 这里给出debug的时候的map对象
    // map.toString() = {side=provider, application=dubbo-server, dubbo=2.5.3, pid=10554, interface=com.grimmjx.edu.HelloService, timeout=100, anyhost=true, timestamp=1559890675368}
    /** 第一部分结束 **/

    /** 第二部分开始 **/
    // 这段if里做的事情主要是检测<dubbo:method> 标签中的配置信息，填充map
    if (CollectionUtils.isNotEmpty(methods)) {
        for (MethodConfig method : methods) {
            // 添加MethodConfig到map中，key=方法名.属性 value=属性值
            // ex   sayHello.retries:2
            appendParameters(map, method, method.getName());
            String retryKey = method.getName() + ".retry";
            if (map.containsKey(retryKey)) {
                String retryValue = map.remove(retryKey);
                if ("false".equals(retryValue)) {
                    map.put(method.getName() + ".retries", "0");
                }
            }
            
            // 获取ArgumentConfig列表
            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())) {
                                            // 添加ArgumentConfig信息到map中
                                            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
    }
    /** 第二部分结束 **/

    /** 第三部分开始 **/
    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);
        }

        // 生成包装类
        String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
        // 添加方法到map中
        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)), ","));
        }
    }

    // 添加token
    if (!ConfigUtils.isEmpty(token)) {
        if (ConfigUtils.isDefault(token)) {
            map.put(TOKEN_KEY, UUID.randomUUID().toString());
        } else {
            map.put(TOKEN_KEY, token);
        }
    }

    // export service
    // 此处map.toString() = {side=provider, application=dubbo-server, methods=hello, dubbo=2.5.3, pid=10554, interface=com.grimmjx.edu.HelloService, timeout=100, anyhost=true, timestamp=1559890675368}
    String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
    Integer port = this.findConfigedPorts(protocolConfig, name, map);
    // 此处url=dubbo://192.168.5.16:20880/com.grimmjx.edu.HelloService?anyhost=true&application=dubbo-server&dubbo=2.5.3&interface=com.grimmjx.edu.HelloService&methods=hello&pid=11917&side=provider&timeout=100&timestamp=1559973693109
    URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);
    if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class).hasExtension(url.getProtocol())) {
        url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
                .getExtension(url.getProtocol()).getConfigurator(url).configure(url);
    }
    /** 第三部分结束 **/

    /** 第四部分开始 **/
    // 开始发布服务
    String scope = url.getParameter(SCOPE_KEY);
    // don't export when none is configured
    // //配置为none不暴露
    if (!SCOPE_NONE.equalsIgnoreCase(scope)) {

        // export to local if the config is not remote (export to remote only when config is remote)
        // 配置不是remote的情况下做本地暴露 (配置为remote，则表示只暴露远程服务)
        if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) {
            exportLocal(url);
        }
        // export to remote if the config is not local (export to local only when config is local)
        // 如果配置不是local则暴露为远程服务.(配置为local，则表示只暴露远程服务)
        if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) {
            if (!isOnlyInJvm() && logger.isInfoEnabled()) {
                logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
            }
            if (CollectionUtils.isNotEmpty(registryURLs)) {
                // 发布服务
                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));
                    URL monitorUrl = loadMonitor(registryURL);
                    if (monitorUrl != null) {
                        url = url.addParameterAndEncoded(MONITOR_KEY, monitorUrl.toFullString());
                    }
                    if (logger.isInfoEnabled()) {
                        logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
                    }

                    // 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);
                    }

                    // 生成Invoker
                    // Invoker是十分重要的对象，可向它发起invoke调用
                    Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
                    // 持有this和invoker
                    // 此处的invoker.getUrl()=registry://127.0.0.1:2181/com.alibaba.dubbo.registry.RegistryService?application=dubbo-server&dubbo=2.5.3&export=dubbo%3A%2F%2F192.168.5.16%3A20880%2Fcom.grimmjx.edu.HelloService%3Fanyhost%3Dtrue%26application%3Ddubbo-server%26dubbo%3D2.5.3%26interface%3Dcom.grimmjx.edu.HelloService%26methods%3Dhello%26pid%3D10738%26side%3Dprovider%26timeout%3D100%26timestamp%3D1559895851366&pid=10738&registry=zookeeper&timestamp=1559895851283
                    DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);

                    // 发布，并生成Exporter
                    Exporter<?> exporter = protocol.export(wrapperInvoker);
                    exporters.add(exporter);
                }

                // 没有注册中心，仅发布服务
            } else {
                Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, url);
                DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);

                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);
    /** 第四部分结束 **/
}

6.org.apache.dubbo.registry.integration.RegistryProtocol#export，为什么是RegistryProtocol？注释里写的很清楚了，这里的url是registry://开头的。

public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
    // 获取注册地址
    URL registryUrl = getRegistryUrl(originInvoker);
    // url to export locally
    // 获取provider url
    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.
    final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
    final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
    overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
    // 要注册的url
    providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
    //export invoker
    // 导出服务
    final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);
    // url to registry
　　　　....
}

　　之后上面调用顺序图的蓝色部分的代码不做分析，主要是创建一个NettyServer（默认）。可自行研究

 

三.服务注册

调用顺序

　　首先讲一下大致的服务注册的调用顺序图，我们只分析红色部分。

-org.apache.dubbo.registry.integration.RegistryProtocol#register

　　-org.apache.dubbo.registry.support.AbstractRegistryFactory#getRegistry

　　　　-org.apache.dubbo.registry.zookeeper.ZookeeperRegistryFactory#createRegistry

　　　　　　-org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#ZookeeperRegistry

　　-org.apache.dubbo.registry.support.FailbackRegistry#register

　　　　-org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#doRegister

源码分析

1.org.apache.dubbo.registry.support.AbstractRegistryFactory#getRegistry，具体还要看下一步

@Override
public Registry getRegistry(URL url) {
    url = URLBuilder.from(url)
            .setPath(RegistryService.class.getName())
            .addParameter(INTERFACE_KEY, RegistryService.class.getName())
            .removeParameters(EXPORT_KEY, REFER_KEY)
            .build();
    String key = url.toServiceStringWithoutResolving();
    // Lock the registry access process to ensure a single instance of the registry
    LOCK.lock();
    try {
        // 缓存中获取
        Registry registry = REGISTRIES.get(key);
        if (registry != null) {
            return registry;
        }
        
        //create registry by spi/ioc
        // 用Dubbo SPI创建Registry
        registry = createRegistry(url);
        if (registry == null) {
            throw new IllegalStateException("Can not create registry " + url);
        }
        // 写入缓存
        REGISTRIES.put(key, registry);
        return registry;
    } finally {
        // Release the lock
        LOCK.unlock();
    }
}

2.org.apache.dubbo.registry.zookeeper.ZookeeperRegistryFactory#createRegistry，创建一个ZooKeeperRegistry实例并返回

@Override
public Registry createRegistry(URL url) {
    return new ZookeeperRegistry(url, zookeeperTransporter);
}

3.org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#ZookeeperRegistry，主要做的就是利用zk创建Zk客户端

public ZookeeperRegistry(URL url, ZookeeperTransporter zookeeperTransporter) {
    super(url);
    if (url.isAnyHost()) {
        throw new IllegalStateException("registry address == null");
    }
    String group = url.getParameter(GROUP_KEY, DEFAULT_ROOT);
    if (!group.startsWith(PATH_SEPARATOR)) {
        group = PATH_SEPARATOR + group;
    }
    this.root = group;
    zkClient = zookeeperTransporter.connect(url);
    zkClient.addStateListener(state -> {
        if (state == StateListener.RECONNECTED) {
            try {
                recover();
            } catch (Exception e) {
                logger.error(e.getMessage(), e);
            }
        }
    });
}

4.org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#doRegister，连接好zk后，是不是就要创建服务提供者的节点了？所以这一步就是注册服务

@Override
public void doRegister(URL url) {
    try {
        // toUrlPath(url) = /dubbo/com.grimmjx.edu.HelloService/providers/dubbo%3A%2F%2F192.168.5.16%3A20880%2Fcom.grimmjx.edu.HelloService%3Fanyhost%3Dtrue%26application%3Ddubbo-server%26dubbo%3D2.5.3%26interface%3Dcom.grimmjx.edu.HelloService%26methods%3Dhello%26pid%3D11917%26side%3Dprovider%26timeout%3D100%26timestamp%3D1559973693109
        zkClient.create(toUrlPath(url), url.getParameter(DYNAMIC_KEY, true));
    } catch (Throwable e) {
        throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
    }
}

这一步之后，我们用zkCli来连接zk看一下节点数据