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搞懂Dubbo服务发布与服务注册

2019-06-08 16:17 1626 查看

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.geek-share.com/detail/2770652300.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

 

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