完整流程图
Dubbo基础篇 服务暴露流程图.png
一句话概括流程
在SpringIOC容器刷新完毕后 (export方法 ContenxtRefreshEvent)，根据配置参数组装成URL，通过 proxyFactory.getInvoker ，利用javassist进行对象代理，封装真正的实现类，然后通过URL参数选择对应的协议进行protocol.export（默认dubbo协议）。在Producer第一次暴露的时候会调用 createServer 来创建 Server（默认NettyServer），然后将 export 得到的 exporter 存入Map（后面处理请求时查找），然后向注册中心注册提供者的信息
具体可以概括为四点
组装URL
创建Invoker代理类，封装真正的实现类
-
打开NettyServer，通过URL选择对应的协议暴露（产生Exporter对象）
-
Exporter对象中会去构建一个调用过滤链（org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper#buildInvokerChain）
Dubbo基础篇 调用过滤链.png
-
- 向注册中心注册提供者信息
入口关键类 ServiceConfig
入口方法
服务暴露的入口方法
主要做的事情是：扫描ServiceConfig，逐个去进行服务的暴露
private void exportServices() {
// 遍历service
configManager.getServices().forEach(sc -> {
// TODO, compatible with ServiceConfig.export()
ServiceConfig serviceConfig = (ServiceConfig) sc;
serviceConfig.setBootstrap(this);
if (exportAsync) {
ExecutorService executor = executorRepository.getServiceExporterExecutor();
Future future = executor.submit(() -> {
sc.export();
exportedServices.add(sc);
});
asyncExportingFutures.add(future);
} else {
sc.export();
exportedServices.add(sc);
}
});
}
private void doExportUrls() {
ServiceRepository repository = ApplicationModel.getServiceRepository();
ServiceDescriptor serviceDescriptor = repository.registerService(getInterfaceClass());
// 往内存中添加provider
repository.registerProvider(
getUniqueServiceName(),
ref,
serviceDescriptor,
this,
serviceMetadata
);
// 获取当前服务的注册中心URL（支持多注册中心）
List registryURLs = ConfigValidationUtils.loadRegistries(this, true);
// 遍历协议，并在每个协议下暴露服务
for (ProtocolConfig protocolConfig : protocols) {
String pathKey = URL.buildKey(getContextPath(protocolConfig)
.map(p -> p + "/" + path)
.orElse(path), group, version);
// In case user specified path, register service one more time to map it to path.
// 注册dubbo service(放入到map中)
repository.registerService(pathKey, interfaceClass);
// TODO, uncomment this line once service key is unified
serviceMetadata.setServiceKey(pathKey);
// 暴露(将上面存入的dubbo service,生成invoker,再包装成export暴露)
doExportUrlsFor1Protocol(protocolConfig, registryURLs);
}
}
前面有一大段都是在进行URL的组装的，这边就不细讲了，具体的可以看下代码的注释
private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List registryURLs) {
// ============================== URL组装前的准备 ==============================
String name = protocolConfig.getName();
if (StringUtils.isEmpty(name)) {
name = DUBBO;
}
Map map = new HashMap();
map.put(SIDE_KEY, PROVIDER_SIDE);
ServiceConfig.appendRuntimeParameters(map);
AbstractConfig.appendParameters(map, getMetrics());
AbstractConfig.appendParameters(map, getApplication());
AbstractConfig.appendParameters(map, getModule());
// ... 此处省略URL组装前的准备流程
// ============================== URL组装完成 ==============================
// 构建URL
URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);
// url的内容
// dubbo://10.167.10.19:20880/org.apache.dubbo.demo.DemoService?anyhost=true&application=dubbo-demo-api-provider&bind.ip=10.167.10.19&bind.port=20880&default=true&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=org.apache.dubbo.demo.DemoService&methods=sayHello,sayHelloAsync&pid=43793&release=&side=provider×tamp=1631080120436
// You can customize Configurator to append extra parameters
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
// 如果scope为SCOPE_NONE不暴露服务
if (!SCOPE_NONE.equalsIgnoreCase(scope)) {
// export to local if the config is not remote (export to remote only when config is remote)
// 本地暴露
if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) {
// 有一个本地暴露，只所以需要本地暴露是考虑到同一个服务内假如需要调用当前的dubbo接口，则可以直接走jvm内部(injvm),减少网络间的通讯
// 修改url协议为injvm
exportLocal(url);
}
// export to remote if the config is not local (export to local only when config is local)
// 远程暴露
if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) {
// 注册中心不为空
if (CollectionUtils.isNotEmpty(registryURLs)) {
// 遍历注册中心
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 = ConfigValidationUtils.loadMonitor(this, 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);
}
// 生成Invoker对象(动态代理创建 javassist)
Invoker invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
// 包装
DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
// provider 需要将 invoker 封装成 expoter(并在此处进行注册)
Exporter exporter = PROTOCOL.export(wrapperInvoker);
exporters.add(exporter);
}
} else {
// 直连方式
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);
Exporter exporter = PROTOCOL.export(wrapperInvoker);
exporters.add(exporter);
}
// 元数据存储
MetadataUtils.publishServiceDefinition(url);
}
}
this.urls.add(url);
}
默认情况下 ，我们的scope为null，他会进行本地暴露+远程暴露
那么从上面的代码我们可以看出，主要是做了两件事情：
- URL的组装
- 本地暴露+远程暴露
为什么需要本地暴露呢？
因为有可能会存在自己的服务调用自己暴露的接口的情况，假如这种情况还走远程调用的话，效率肯定没有jvm内部的本地调用高
生成Invoker对象
Invoker invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
以Javassist为例（默认为Javassist）
@Override
public Invoker getInvoker(T proxy, Class type, URL url) {
// TODO Wrapper cannot handle this scenario correctly: the classname contains '$'
// 通过Javaassist封装成Wrapper类（Dubbo服务启动时生成，所以在运行时不会产生开销），减少反射的调用
// Wrapper.getWrapper -> 反射获取对应的类信息，包装成Wrapper对象
final Wrapper wrapper = Wrapper.getWrapper(proxy.getClass().getName().indexOf('$') < 0 ? proxy.getClass() : type);
return new AbstractProxyInvoker(proxy, type, url) {
@Override
// Wrapper最终调用最终调用服务提供者的接口实现类的方法
protected Object doInvoke(T proxy, String methodName,
Class[] parameterTypes,
Object[] arguments) throws Throwable {
return wrapper.invokeMethod(proxy, methodName, parameterTypes, arguments);
}
};
}
为什么需要Wrapper类修饰
目的：减少反射调用的开销
Dubbo基础篇 为什么需要Wrapper类修饰1.png
Dubbo基础篇 为什么需要Wrapper类修饰2.png
暴露操作
Exporter exporter = PROTOCOL.export(wrapperInvoker)
关于此处重点看两个类
RegisterProtocol
@Override
public Exporter export(final Invoker originInvoker) throws RpcException {
// 获取注册中心URL
URL registryUrl = getRegistryUrl(originInvoker);
// url to export locally
// 获取提供者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);
providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
//export invoker
// 选择具体的协议去暴露服务
// 以DubboProtocol为例，最终调用到DubboProtocol
final ExporterChangeableWrapper exporter = doLocalExport(originInvoker, providerUrl);
// url to registry
// 获取注册中心
final Registry registry = getRegistry(originInvoker);
final URL registeredProviderUrl = getUrlToRegistry(providerUrl, registryUrl);
// decide if we need to delay publish
boolean register = providerUrl.getParameter(REGISTER_KEY, true);
if (register) {
// 注册服务
register(registryUrl, registeredProviderUrl);
}
// register stated url on provider model
registerStatedUrl(registryUrl, registeredProviderUrl, register);
exporter.setRegisterUrl(registeredProviderUrl);
exporter.setSubscribeUrl(overrideSubscribeUrl);
// Deprecated! Subscribe to override rules in 2.6.x or before.
// 订阅
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
notifyExport(exporter);
//Ensure that a new exporter instance is returned every time export
return new DestroyableExporter<>(exporter);
}
DubboProtocol
@Override
public Exporter export(Invoker invoker) throws RpcException {
URL url = invoker.getUrl();
// export service.
// 创建ServiceKey
String key = serviceKey(url);
// 将上层传入的Invoker对象封装成DubboExporter对象，然后记录到exporterMap集合中
DubboExporter exporter = new DubboExporter(invoker, key, exporterMap);
exporterMap.put(key, exporter);
//export an stub service for dispatching event
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."));
}
}
}
// 启动ProtocolServer
openServer(url);
// 进行序列化的优化处理
optimizeSerialization(url);
return exporter;
}
打开一个服务
以当前的机器的（ip:port）为key，查看缓存中是否存在Server，没有则创建一个
不同协议暴露的端口不同，例如http协议可以选择8080端口之类的，dubbo协议为20880
默认 NettyServer
private ProtocolServer createServer(URL url) {
url = URLBuilder.from(url)
// send readonly event when server closes, it's enabled by default
// readonlty请求是否阻塞等待
.addParameterIfAbsent(CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString())
// enable heartbeat by default
// 心跳间隔
.addParameterIfAbsent(HEARTBEAT_KEY, String.valueOf(DEFAULT_HEARTBEAT))
// Codec2扩展实现
.addParameter(CODEC_KEY, DubboCodec.NAME)
.build();
// 检测SERVER_KEY参数指定的Transporter扩展实现是否合法
String str = url.getParameter(SERVER_KEY, DEFAULT_REMOTING_SERVER);
if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
throw new RpcException("Unsupported server type: " + str + ", url: " + url);
}
ExchangeServer server;
try {
// 通过Exchangers门面类，创建ExchangeServer对象
// 处理consumer的请求
// handler -> 对应netty的handler
server = Exchangers.bind(url, requestHandler);
} catch (RemotingException e) {
throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);
}
// 检测CLIENT_KEY参数指定的Transporter扩展实现是否合法
str = url.getParameter(CLIENT_KEY);
if (str != null && str.length() > 0) {
Set supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
if (!supportedTypes.contains(str)) {
throw new RpcException("Unsupported client type: " + str);
}
}
// 将ExchangeServer封装成DubboProtocolServer返回
return new DubboProtocolServer(server);
}
注册到注册中心
@Override
public Registry getRegistry(URL url) {
if (destroyed.get()) {
LOGGER.warn("All registry instances have been destroyed, failed to fetch any instance. " +
"Usually, this means no need to try to do unnecessary redundant resource clearance, all registries has been taken care of.");
return DEFAULT_NOP_REGISTRY;
}
url = URLBuilder.from(url)
.setPath(RegistryService.class.getName())
.addParameter(INTERFACE_KEY, RegistryService.class.getName())
.removeParameters(EXPORT_KEY, REFER_KEY)
.build();
String key = createRegistryCacheKey(url);
// Lock the registry access process to ensure a single instance of the registry
LOCK.lock();
try {
Registry registry = REGISTRIES.get(key);
if (registry != null) {
return registry;
}
//create registry by spi/ioc
// 创建注册中心实例
registry = createRegistry(url);
if (registry == null) {
throw new IllegalStateException("Can not create registry " + url);
}
REGISTRIES.put(key, registry);
return registry;
} finally {
// Release the lock
LOCK.unlock();
}
}
@Override
public void register(URL url) {
// 注册服务
this.register(new com.alibaba.dubbo.common.URL(url));
}