一、前言
前面有说到Dubbo的服务发现机制,也就是SPI,那既然Dubbo内部实现了更加强大的服务发现机制,现在我们就来一起看看Dubbo在发现服务后需要做什么才能将服务注册到注册中心中。
二、Dubbo服务注册简介
首先需要明白的是Dubbo是依赖于Spring容器的,Dubbo服务注册过程也是始于Spring容器发布刷新事件。而后Dubbo在接收到事件后,就会进行服务注册,整个逻辑大致分为三个部分:
-
1、检查参数,组装URL:服务消费方是通过URL拿到服务提供者的,所以我们需要为服务提供者配置好对应的URL。
-
2、导出服务到本地和远程:这里的本地指的是JVM,远程指的是实现invoke,使得服务消费方能够通过invoke调用到服务。
-
3、向注册中心注册服务:能够让服务消费方知道服务提供方提供了那个服务。
三、接收Spring容器刷新事件
Dubbo服务注册是始于Spring容器发布刷新事件。
DubboBootstrap的启动是由start方法完成的,start方法的执行成功,意味着dubbo的启动结束。服务端服务的暴露就是在start方法中完成的。
一般使用dubbo框架的都会引入Spring框架,Spring框架有一个事件监听机制,dubbo正是监听Spring的上下文刷新事件ContextRefreshedEvent,来启动Dubbo服务的。这个服务监听类就是DubboBootstrapApplicationListener。
public class DubboBootstrapApplicationListener extends OnceApplicationContextEventListener implements Ordered {
private final DubboBootstrap dubboBootstrap;
public DubboBootstrapApplicationListener(ApplicationContext applicationContext) {
super(applicationContext);
this.dubboBootstrap = DubboBootstrap.getInstance();
DubboBootstrapStartStopListenerSpringAdapter.applicationContext = applicationContext;
}
@Override
public void onApplicationContextEvent(ApplicationContextEvent event) {
if (event instanceof ContextRefreshedEvent) {
onContextRefreshedEvent((ContextRefreshedEvent) event);
} else if (event instanceof ContextClosedEvent) {
onContextClosedEvent((ContextClosedEvent) event);
}
}
private void onContextRefreshedEvent(ContextRefreshedEvent event) {
dubboBootstrap.start();
}
}
从上面代码可以看出,当发生ContextRefreshedEvent事件的时候,dubbo调用DubboBootstrap的start方法。
四、start方法详解
DubboBootstrap是一个dubbo框架启动的帮助类,他有一个start()方法,在该方法的内部就会调用exportServices()用于导出服务,和调用referServices()进行引用服务。
public class DubboBootstrap extends GenericEventListener {
public DubboBootstrap start() {
//只能初始化一次
if (started.compareAndSet(false, true)) {
ready.set(false);
//调用初始化方法
initialize();
if (logger.isInfoEnabled()) {
logger.info(NAME + " is starting...");
}
// 1. export Dubbo Services
exportServices();
// Not only provider register
if (!isOnlyRegisterProvider() || hasExportedServices()) {
// 2. export MetadataService
exportMetadataService();
//3. Register the local ServiceInstance if required
registerServiceInstance();
}
referServices();
if (asyncExportingFutures.size() > 0) {
new Thread(() -> {
try {
this.awaitFinish();
} catch (Exception e) {
logger.warn(NAME + " exportAsync occurred an exception.");
}
ready.set(true);
if (logger.isInfoEnabled()) {
logger.info(NAME + " is ready.");
}
ExtensionLoader<DubboBootstrapStartStopListener> exts = getExtensionLoader(DubboBootstrapStartStopListener.class);
exts.getSupportedExtensionInstances().forEach(ext -> ext.onStart(this));
}).start();
} else {
ready.set(true);
if (logger.isInfoEnabled()) {
logger.info(NAME + " is ready.");
}
ExtensionLoader<DubboBootstrapStartStopListener> exts = getExtensionLoader(DubboBootstrapStartStopListener.class);
exts.getSupportedExtensionInstances().forEach(ext -> ext.onStart(this));
}
if (logger.isInfoEnabled()) {
logger.info(NAME + " has started.");
}
}
return this;
}
}
1、initialize方法
在start方法中,也会调用initialize方法,之前提到过,服务端启动的时候,dubbo在start方法中调用initialize方法做初始化,而客户端启动的时候会跳过initialize方法。
2、exportServices方法
initialize方法之后调用exportServices方法,该方法用于暴露服务,服务端使用。
public class DubboBootstrap extends GenericEventListener {
private final ConfigManager configManager;
private void exportServices() {
//创建的每个ServiceConfig对象都添加到configManager,下面获取所有的ServiceConfig对象并遍历
configManager.getServices().forEach(sc -> {
// TODO, compatible with ServiceConfig.export()
ServiceConfig serviceConfig = (ServiceConfig) sc;
serviceConfig.setBootstrap(this);
if (exportAsync) {
//异步暴露,使用线程池暴露服务
ExecutorService executor = executorRepository.getServiceExporterExecutor();
Future<?> future = executor.submit(() -> {
sc.export(); //暴露服务
exportedServices.add(sc); //记录所有暴露的服务
});
asyncExportingFutures.add(future);
} else {
sc.export();//暴露服务
exportedServices.add(sc); //记录所有暴露的服务
}
});
}
}
3、isOnlyRegisterProvider方法
isOnlyRegisterProvider方法检查ApplicationConfig的registerConsumer属性,从代码分析,registerConsumer只是用于在这里做了判断,我认为该属性无用,可以不用配置。
4、hasExportedServices方法
hasExportedServices()检查是否配置元数据中心的url,如果配置了,返回true。
5、exportMetadataService方法
exportMetadataService方法用于暴露本地元数据服务,initMetadataServiceExporter方法里面建立了对象metadataServiceExporter,然后在这里暴露服务。服务暴露后客户端可以使用MetadataService接口方法查看dubbo实例的元数据,服务是以dubbo服务形式发布的。
public class DubboBootstrap extends GenericEventListener {
private volatile MetadataServiceExporter metadataServiceExporter;
private void exportMetadataService() {
metadataServiceExporter.export();
}
}
6、registerServiceInstance方法
registerServiceInstance用于将dubbo实例注册到专用于服务发现的注册中心。
public class DubboBootstrap extends GenericEventListener {
private void registerServiceInstance() {
if (CollectionUtils.isEmpty(getServiceDiscoveries())) {
return;
}
ApplicationConfig application = getApplication();
String serviceName = application.getName();
URL exportedURL = selectMetadataServiceExportedURL();
String host = exportedURL.getHost();
int port = exportedURL.getPort();
//创建ServiceInstance对象,该对象中持有下面方法的入参值,以及注册中心的类型,默认是local。
//ServiceInstance代表了一个dubbo实例,其他dubbo实例可以通过ServiceInstance的属性信息找到本实例的位置
ServiceInstance serviceInstance = createServiceInstance(serviceName, host, port);
//获取所有的注册中心,将ServiceInstance对象注册到注册中心,
//这里的注册中心实现了ServiceDiscovery接口,是专用于服务发现的。
doRegisterServiceInstance(serviceInstance);
// scheduled task for updating Metadata and ServiceInstance
executorRepository.nextScheduledExecutor().scheduleAtFixedRate(() -> {
InMemoryWritableMetadataService localMetadataService = (InMemoryWritableMetadataService) WritableMetadataService.getDefaultExtension();
localMetadataService.blockUntilUpdated();
ServiceInstanceMetadataUtils.refreshMetadataAndInstance();
}, 0, ConfigurationUtils.get(METADATA_PUBLISH_DELAY_KEY, DEFAULT_METADATA_PUBLISH_DELAY), TimeUnit.MICROSECONDS);
}
private void doRegisterServiceInstance(ServiceInstance serviceInstance) {
//FIXME
publishMetadataToRemote(serviceInstance);
getServiceDiscoveries().forEach(serviceDiscovery ->
{
calInstanceRevision(serviceDiscovery, serviceInstance);
// register metadata
serviceDiscovery.register(serviceInstance);
});
}
}
7、referServices方法
referServices方法用于处理ReferenceConfig对象。
public class DubboBootstrap extends GenericEventListener {
private void referServices() {
if (cache == null) {
cache = ReferenceConfigCache.getCache();
}
configManager.getReferences().forEach(rc -> {
// TODO, compatible with ReferenceConfig.refer()
ReferenceConfig referenceConfig = (ReferenceConfig) rc;
referenceConfig.setBootstrap(this);
if (rc.shouldInit()) {
if (referAsync) {
CompletableFuture<Object> future = ScheduledCompletableFuture.submit(
executorRepository.getServiceExporterExecutor(),
() -> cache.get(rc)
);
asyncReferringFutures.add(future);
} else {
cache.get(rc);
}
}
});
}
}
在我们平常编写provider的接口实现类时,都会打上@Service注解,从而这个标注这个类属于ServiceBean。
而DubboBootstrap中的start()方法最终会调用到ServiceBean类中的exported()方法。
这就是Dubbo服务导出到注册中心过程的起点。需要我们在服务接口实现类上打上@Service。ServiceBean是Dubbo与Spring 框架进行整合的关键,可以看做是两个框架之间的桥梁。具有同样作用的类还有ReferenceBean。
五、检查配置参数以及URL装配
1、检查配置
在这一阶段Dubbo需要检查用户的配置是否合理,或者为用户补充缺省配置。就是从刷新事件开始,进入export()方法,源码解析如下:
public class ServiceConfig<T> extends ServiceConfigBase<T> {
public synchronized void export() {
if (bootstrap == null) {
bootstrap = DubboBootstrap.getInstance();
bootstrap.initialize();
}
//检查并且更新配置
checkAndUpdateSubConfigs();
//init serviceMetadata
serviceMetadata.setVersion(getVersion());
serviceMetadata.setGroup(getGroup());
serviceMetadata.setDefaultGroup(getGroup());
serviceMetadata.setServiceType(getInterfaceClass());
serviceMetadata.setServiceInterfaceName(getInterface());
serviceMetadata.setTarget(getRef());
//是否需要导出
if (!shouldExport()) {
return;
}
//是否需要延时
if (shouldDelay()) {
DELAY_EXPORT_EXECUTOR.schedule(this::doExport, getDelay(), TimeUnit.MILLISECONDS);
} else {
//立刻导出
doExport();
}
//导出后
exported();
}
}
public class ServiceConfig<T> extends ServiceConfigBase<T> {
private void checkAndUpdateSubConfigs() {
// Use default configs defined explicitly with global scope
//检查配置项包括provider是否存在,导出端口是否可用,注册中心是否可以连接等等
// 使用全局范围显式定义的默认配置
// <dubbo:provider/> <dubbo:protocol/>
completeCompoundConfigs();
checkDefault();
checkProtocol();
// init some null configuration.
// 初始化一些空设置
List<ConfigInitializer> configInitializers = ExtensionLoader.getExtensionLoader(ConfigInitializer.class)
.getActivateExtension(URL.valueOf("configInitializer://"), (String[]) null);
configInitializers.forEach(e -> e.initServiceConfig(this));
// if protocol is not injvm checkRegistry
if (!isOnlyInJvm()) {
//如果protocol不是内部调用(injvm)
//检查registry设置
checkRegistry();
}
//检查接口内部方法是否不为空
//environment中的值覆盖service属性
this.refresh();
if (StringUtils.isEmpty(interfaceName)) {
//interface属性必需
throw new IllegalStateException("<dubbo:service interface=\"\" /> interface not allow null!");
}
if (ref instanceof GenericService) {
//如果实际Bean实现了GenericService接口,常用服务bean
interfaceClass = GenericService.class;
if (StringUtils.isEmpty(generic)) {
generic = Boolean.TRUE.toString();
}
} else {
try {
//不是GenericService接口类型,根据interfaceClass = Class.forName(interfaceName)
interfaceClass = Class.forName(interfaceName, true, Thread.currentThread()
.getContextClassLoader());
} catch (ClassNotFoundException e) {
throw new IllegalStateException(e.getMessage(), e);
}
//检查接口方法都实现了
checkInterfaceAndMethods(interfaceClass, getMethods());
checkRef();
generic = Boolean.FALSE.toString();
}
if (local != null) {
//配置<dubbo:service local="true"/>时
if ("true".equals(local)) {
local = interfaceName + "Local";
}
Class<?> localClass;
try {
//初始化代理类localClass = ClassforName(interfaceName+"Local")
localClass = ClassUtils.forNameWithThreadContextClassLoader(local);
} catch (ClassNotFoundException e) {
throw new IllegalStateException(e.getMessage(), e);
}
if (!interfaceClass.isAssignableFrom(localClass)) {
throw new IllegalStateException("The local implementation class " + localClass.getName() + " not implement interface " + interfaceName);
}
}
if (stub != null) {
//配置<dubbo:service local="true"/>时
if ("true".equals(stub)) {
stub = interfaceName + "Stub";
}
Class<?> stubClass;
try {
//初始化代理类stubClass = ClassforName(interfaceName+"Local")
stubClass = ClassUtils.forNameWithThreadContextClassLoader(stub);
} catch (ClassNotFoundException e) {
throw new IllegalStateException(e.getMessage(), e);
}
if (!interfaceClass.isAssignableFrom(stubClass)) {
throw new IllegalStateException("The stub implementation class " + stubClass.getName() + " not implement interface " + interfaceName);
}
}
//检查若配置了local或stub,localClass或stubClass必须是interfaceClass的子类
checkStubAndLocal(interfaceClass);
ConfigValidationUtils.checkMock(interfaceClass, this);
//检查serviceconfig的属性
ConfigValidationUtils.validateServiceConfig(this);
//配置后置处理器ConfigPostProcess,类似于BeanPostProcessor
postProcessConfig();
}
}
上面的源码分析可看出。export方法主要检查的配置项有@Service标签的类是否属性合法。服务提供者是否存在,是否有对应的Application启动,端口是否能连接,是否有对应的注册中心等等一些配置,在检查完这些配置后Dubbo会识别我们此次启动服务是想在本地启动进行一些调试,还是将服务暴露给别人。不想暴露出去可以进行配置。
<dubbo:provider export="false" />
2、URL装配
在Dubbo中的URL一般包括以下字段:protocol、host、port、path、parameters。在检查配置后会进入到doExport中。
- protocol:就是URL最前面的字段,表示的是协议,一般是:dubbo thrift http zk
- host.port:就是对应的IP地址和端口
- path:接口名称
- parameters:参数键值对
public class ServiceConfig<T> extends ServiceConfigBase<T> {
protected synchronized void doExport() {
if (unexported) {
throw new IllegalStateException("The service " + interfaceClass.getName() + " has already unexported!");
}
//已注册的直接返回
if (exported) {
return;
}
exported = true;
if (StringUtils.isEmpty(path)) {
//设置path默认值为接口名
path = interfaceName;
}
doExportUrls();
}
}
进入到doExportUrls
public class ServiceConfig<T> extends ServiceConfigBase<T> {
private void doExportUrls() {
//前面创建服务仓库ServiceRepository
ServiceRepository repository = ApplicationModel.getServiceRepository();
//将Service注册到服务仓库ServiceRepository的services中
ServiceDescriptor serviceDescriptor = repository.registerService(getInterfaceClass());
//将Service注册到服务仓库ServiceRepository的providers中
repository.registerProvider(
getUniqueServiceName(),
ref,
serviceDescriptor,
this,
serviceMetadata
);
//生成registryURLs格式如下
// registry://mcip:2291/org.apache.dubbo.registry.RegistryService?application=dubbo-demo&backup=mcip:2292,mcip:2293&dubbo=2.0.2&pid=13252®istry=zookeeper&release=2.7.5×tamp=1584191484814
List<URL> registryURLs = ConfigValidationUtils.loadRegistries(this, true);
//<dubbo:protocol name="dubbo" port="${dubbo.port}" />
for (ProtocolConfig protocolConfig : protocols) {
//服务路径=protocol的contexpath属性+service的path+group+version
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.
// 如果指定了特殊路径,再次注入到服务仓库ServiceRepository的services中,
// 未指定同名覆盖
repository.registerService(pathKey, interfaceClass);
// TODO, uncomment this line once service key is unified
//设置到serviceMetadata中
serviceMetadata.setServiceKey(pathKey);
//注册
doExportUrlsFor1Protocol(protocolConfig, registryURLs);
}
}
}
进入到加载注册中心链接的方法
public class ConfigValidationUtils {
public static List<URL> loadRegistries(AbstractInterfaceConfig interfaceConfig, boolean provider) {
// check && override if necessary
List<URL> registryList = new ArrayList<URL>();
ApplicationConfig application = interfaceConfig.getApplication();
List<RegistryConfig> registries = interfaceConfig.getRegistries();
if (CollectionUtils.isNotEmpty(registries)) {
for (RegistryConfig config : registries) {
String address = config.getAddress();
if (StringUtils.isEmpty(address)) {
address = ANYHOST_VALUE;
}
// 判断当前注册中心的地址是否为可用地址,不可用地址格式为 N/A
if (!RegistryConfig.NO_AVAILABLE.equalsIgnoreCase(address)) {
Map<String, String> map = new HashMap<String, String>();
// 添加 ApplicationConfig 中的字段信息到 map 中
AbstractConfig.appendParameters(map, application);
// 添加 RegistryConfig 字段信息到 map 中
AbstractConfig.appendParameters(map, config);
// 添加 path,protocol 等信息到 map 中
map.put(PATH_KEY, RegistryService.class.getName());
AbstractInterfaceConfig.appendRuntimeParameters(map);
// 如果注册中心配置中没有配置protocol,则默认用dubbo
if (!map.containsKey(PROTOCOL_KEY)) {
map.put(PROTOCOL_KEY, DUBBO_PROTOCOL);
}
// 解析得到 URL 列表,address 可能包含多个注册中心 ip,
// 因此解析得到的是一个 URL 列表
List<URL> urls = UrlUtils.parseURLs(address, map);
// 重新构建URL
for (URL url : urls) {
// 将 URL 协议头设置为 registry
url = URLBuilder.from(url)
.addParameter(REGISTRY_KEY, url.getProtocol())
.setProtocol(extractRegistryType(url))
.build();
// 满足两个条件会往里添加:1、是提供者且有配置注册中心;2、不是提供者但是配置了订阅
// 通过判断条件,决定是否添加 url 到 registryList 中,条件如下:
// (服务提供者 && register = true 或 null) || (非服务提供者 && subscribe = true 或 null)
if ((provider && url.getParameter(REGISTER_KEY, true))
|| (!provider && url.getParameter(SUBSCRIBE_KEY, true))) {
//添加url到registryList中
registryList.add(url);
}
}
}
}
}
return genCompatibleRegistries(registryList, provider);
}
}
loadRegistries方法主要包含如下的逻辑:
- 1、构建参数映射集合,也就是 map
- 2、构建注册中心链接列表
- 3、遍历链接列表,并根据条件决定是否将其添加到 registryList 中
实际上因为Dubbo现如今支持很多注册中心,所以对于一些注册中心的URL也要进行遍历构建。这里是生成注册中心的URL。还未生成Dubbo服务的URL。比如说使用的是Zookeeper注册中心,可能从loadRegistries中拿到的就是:
registry://127.0.0.1:2181/org.apache.dubbo.registry.RegistryService?application=demo-provider&dubbo=2.7.3&pid=1528&qos.port=22222®istry=zookeeper×tamp=1530743640901
这种类型的URL,表示这是一个注册协议,现在可以根据这个URL定位到注册中心去了。服务接口是RegistryService,registry的类型为zookeeper。可是我们还未生成Dubbo服务提供方的URL所以接着看下面代码
然后进行到doExportUrlsFor1Protocol(装配Dubbo服务的URL并且实行发布)
public class ServiceConfig<T> extends ServiceConfigBase<T> {
private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
//首先是将一些信息,比如版本、时间戳、方法名以及各种配置对象的字段信息放入到 map 中
//map 中的内容将作为 URL 的查询字符串。构建好 map 后,紧接着是获取上下文路径、主机名以及端口号等信息。
//最后将 map 和主机名等数据传给 URL 构造方法创建 URL 对象。需要注意的是,这里出现的 URL 并非 java.net.URL,而是 com.alibaba.dubbo.common.URL。
String name = protocolConfig.getName();
// 如果协议名为空,或空串,则将协议名变量设置为 dubbo
if (StringUtils.isEmpty(name)) {
//<dubbo:protocol name=""/>默认为dubbo
name = DUBBO;
}
Map<String, String> map = new HashMap<String, String>();
// 添加 side、版本、时间戳以及进程号等信息到 map 中
map.put(SIDE_KEY, PROVIDER_SIDE);
ServiceConfig.appendRuntimeParameters(map);
// 通过反射将对象的字段信息添加到 map 中
AbstractConfig.appendParameters(map, getMetrics());
AbstractConfig.appendParameters(map, getApplication());
AbstractConfig.appendParameters(map, getModule());
// remove 'default.' prefix for configs from ProviderConfig
// appendParameters(map, provider, Constants.DEFAULT_KEY);
AbstractConfig.appendParameters(map, provider);
AbstractConfig.appendParameters(map, protocolConfig);
AbstractConfig.appendParameters(map, this);
MetadataReportConfig metadataReportConfig = getMetadataReportConfig();
if (metadataReportConfig != null && metadataReportConfig.isValid()) {
map.putIfAbsent(METADATA_KEY, REMOTE_METADATA_STORAGE_TYPE);
}
// methods 为 MethodConfig 集合,MethodConfig 中存储了 <dubbo:method> 标签的配置信息
if (CollectionUtils.isNotEmpty(getMethods())) {
//检测 <dubbo:method> 标签中的配置信息,并将相关配置添加到 map 中
for (MethodConfig method : getMethods()) {
AbstractConfig.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");
}
}
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.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())) {
AbstractConfig.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())) {
AbstractConfig.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) {
AbstractConfig.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
}
//genericService设置
if (ProtocolUtils.isGeneric(generic)) {
map.put(GENERIC_KEY, generic);
map.put(METHODS_KEY, ANY_VALUE);
} else {
//接口版本号,跟随jar包 例如:1.0-SNAPSHOT
String revision = Version.getVersion(interfaceClass, version);
if (revision != null && revision.length() > 0) {
map.put(REVISION_KEY, revision);
}
//接口的方法名数组
String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
if (methods.length == 0) {
logger.warn("No method found in service interface " + interfaceClass.getName());
//空方法标志map.put("methods","*")
map.put(METHODS_KEY, ANY_VALUE);
} else {
//方法数组字符串map.put("methods","insert,update")
map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));
}
}
/**
* Here the token value configured by the provider is used to assign the value to ServiceConfig#token
* Service的token验证
*/
if (ConfigUtils.isEmpty(token) && provider != null) {
token = provider.getToken();
}
if (!ConfigUtils.isEmpty(token)) {
if (ConfigUtils.isDefault(token)) {
map.put(TOKEN_KEY, UUID.randomUUID().toString());
} else {
map.put(TOKEN_KEY, token);
}
}
//init serviceMetadata attachments
//map放入到serviceMetadata中
serviceMetadata.getAttachments().putAll(map);
// export service
// 获取协议host,默认获取本机ip <dubbo:protocol host="" />
String host = findConfigedHosts(protocolConfig, registryURLs, map);
//获取协议port,dubbo默认20880 <dubbo:protocol port="" />
Integer port = findConfigedPorts(protocolConfig, name, map);
//生成url格式如下
//dubbo://192.168.56.1:20880/org.study.service.UserService?anyhost=true&application=dubbo-demo&bind.ip=192.168.56.1&bind.port=20880&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=org.study.service.UserService&methods=getUserById,update,insert,transactionalTest,getUserByUserId,delete&pid=13252&release=2.7.5&revision=1.0-SNAPSHOT&side=provider×tamp=1584192937036
URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);
// 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);
}
//获取作用域scope属性
String scope = url.getParameter(SCOPE_KEY);
// don't export when none is configured
// scope == "none",不注册,一般为null
if (!SCOPE_NONE.equalsIgnoreCase(scope)) {
// export to local if the config is not remote (export to remote only when config is remote)
if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) {
//scope != "remote" ,注册到本地,一般为null会注册到本地
exportLocal(url);
}
// export to remote if the config is not local (export to local only when config is local)
if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) {
//scope != "local" ,注册到注册表,一般为null会注册到注册表
if (CollectionUtils.isNotEmpty(registryURLs)) {
for (URL registryURL : registryURLs) {
//if protocol is only injvm ,not register
if (LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) {
//injvm,内部调用不注册
continue;
}
//url存在dynamic保留,不存在赋值为registryURL的dynamic属性值
url = url.addParameterIfAbsent(DYNAMIC_KEY, registryURL.getParameter(DYNAMIC_KEY));
//监控的url
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
// provider代理属性 一般为null
String proxy = url.getParameter(PROXY_KEY);
if (StringUtils.isNotEmpty(proxy)) {
registryURL = registryURL.addParameter(PROXY_KEY, proxy);
}
//创建一个AbstractProxyInvoker的子类实例new AbstractProxyInvoker(ref, interfaceClass,rul)
Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
//包装器
DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
//默认DubboProtocol.export注册到远程注册表zookeeper中
Exporter<?> exporter = PROTOCOL.export(wrapperInvoker);
exporters.add(exporter);
}
// 不存在注册中心,仅导出服务
} else {
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);
}
MetadataUtils.publishServiceDefinition(url);
}
}
this.urls.add(url);
}
}
上面的源码前半段是进行URL装配,这个URL就是Dubbo服务的URL,大致如下:
dubbo://192.168.1.6:20880/org.apache.dubbo.demo.DemoService?anyhost=true&application=demo-provider&bind.ip=192.168.1.6&bind.port=20880&dubbo=2.7.3&generic=false&interface=org.apache.dubbo.demo.DemoService&methods=sayHello&pid=5744&qos.port=22222&side=provider×tamp=1530746052546
这个URL表示它是一个dubbo协议(DubboProtocol),地址是当前服务器的ip,端口是要暴露的服务的端口号,可以从dubbo:protocol配置,服务接口为dubbo:service配置发布的接口。
后半段主要是判断scope变量来决定是否将服务导出远程或者本地,导出到本地实际上很简单只需要生成Invoker。当导出到远程就需要添加监视器还要生成invoker。监视器能让Dubbo定时查看注册中心挂了没。会抛出指定异常,而invoker使得服务消费方能够远程调用到服务。并且还会进行注册到注册中心下面我们接着来看看服务的发布。因为Invoker比较重要在消费者和提供者中都有,所以这个后面会单独拿出来进行探讨。
五、服务发布本地与远程
1、服务发布到本地
public class ServiceConfig<T> extends ServiceConfigBase<T> {
private void exportLocal(URL url) {
//进行本地URL的构建
URL local = URLBuilder.from(url)
.setProtocol(LOCAL_PROTOCOL)
.setHost(LOCALHOST_VALUE)
.setPort(0)
.build();
//根据本地的URL来实现对应的Invoker
Exporter<?> exporter = PROTOCOL.export(
PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, local));
exporters.add(exporter);
logger.info("Export dubbo service " + interfaceClass.getName() + " to local registry url : " + local);
}
}
String LOCALHOST_VALUE = "127.0.0.1";
String LOCAL_PROTOCOL = "injvm";
可见发布到本地是重新构建了protocol,injvm就是代表在本地的JVM里,host与port都统一默认127.0.0.1:0。
2、服务发布到远程
public class RegistryProtocol implements Protocol {
@Override
public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
//注册url,zookeeper
//zookeeper://mcip:2291/org.apache.dubbo.registry.RegistryService?application=dubbo-demo&backup=mcip:2292,mcip:2293&dubbo=2.0.2&export=dubbo%3A%2F%2F192.168.56.1%3A20880%2Forg.study.service.UserService%3Fanyhost%3Dtrue%26application%3Ddubbo-demo%26bind.ip%3D192.168.56.1%26bind.port%3D20880%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26interface%3Dorg.study.service.UserService%26methods%3DgetUserById%2Cupdate%2Cinsert%2CtransactionalTest%2CgetUserByUserId%2Cdelete%26pid%3D12956%26release%3D2.7.5%26revision%3D1.0-SNAPSHOT%26side%3Dprovider%26timestamp%3D1584262152345&pid=12956&release=2.7.5×tamp=1584262152342
URL registryUrl = getRegistryUrl(originInvoker);
// url to export locally
// 暴露服务的url
//dubbo://192.168.56.1:20880/org.study.service.UserService?anyhost=true&application=dubbo-demo&bind.ip=192.168.56.1&bind.port=20880&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=org.study.service.UserService&methods=getUserById,update,insert,transactionalTest,getUserByUserId,delete&pid=12956&release=2.7.5&revision=1.0-SNAPSHOT&side=provider×tamp=1584262152345
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.
//获取订阅URL,比如:provider://192.168.1.6:20880/......
final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
//url与service绑定,放入容器中,远程调用时根据url找到serviceimpl
final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
//向订阅中心推送监听器
overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);
providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
//export invoker
//导出服务
//注册invoker到本地dubbo.expo
//调用DubboProtocol.export,其中openServer开启netty监听,
final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);
// url to registry
// 最终的注册到zookeeper
final Registry registry = getRegistry(originInvoker);
//获取已注册的服务提供者的URL,比如dubbo://192.168.1.6:20880/.......
final URL registeredProviderUrl = getUrlToRegistry(providerUrl, registryUrl);
// decide if we need to delay publish
// 获取 register 参数
boolean register = providerUrl.getParameter(REGISTER_KEY, true);
// 根据 register 的值决定是否注册服务
if (register) {
register(registryUrl, registeredProviderUrl);
}
// register stated url on provider model
registerStatedUrl(registryUrl, registeredProviderUrl, register);
exporter.setRegisterUrl(registeredProviderUrl);
// 向注册中心进行订阅 override 数据
exporter.setSubscribeUrl(overrideSubscribeUrl);
// Deprecated! Subscribe to override rules in 2.6.x or before.
registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);
//确认注册完
notifyExport(exporter);
//Ensure that a new exporter instance is returned every time export
// 创建并返回 DestroyableExporter
return new DestroyableExporter<>(exporter);
}
}
上面的源码主要是根据前面生成的URL进行服务的发布和注册。当执行到doLocalExport也就是发布本地服务到远程时候会调用 DubboProtocol 的 export 方法大致会经历下面一些步骤来导出服务
-
从Invoker获取providerUrl,构建serviceKey(group/service:version:port),构建DubboExporter并以serviceKey为key放入本地map缓存。
-
处理url携带的本地存根和callback回调。
-
根据url打开服务器端口,暴露本地服务。先以url.getAddress为key查询本地缓存serverMap获取ExchangeServer,如果不存在,则通过createServer创建。
-
createServer方法,设置心跳时间,判断url中的传输方式(key=server,对应Transporter服务)是否支持,设置codec=dubbo,最后根据url和ExchangeHandler对象绑定server返回,这里的ExchangeHandler非常重要,它就是消费方调用时,底层通信层回调的Handler,从而获取包含实际Service实现的Invoker执行器,它是定义在DubboProtocol类中的ExchangeHandlerAdapter内部类。
-
返回DubboExporter对象。
到这里大致的服务发布图如下:
六、服务注册
服务注册操作对于 Dubbo 来说不是必需的,通过服务直连的方式就可以绕过注册中心。但通常我们不会这么做,直连方式不利于服务治理,仅推荐在测试服务时使用。对于 Dubbo 来说,注册中心虽不是必需,但却是必要的。源码如下:
public class RegistryProtocol implements Protocol {
private void register(URL registryUrl, URL registeredProviderUrl) {
Registry registry = registryFactory.getRegistry(registryUrl);
registry.register(registeredProviderUrl);
}
}
public abstract class FailbackRegistry extends AbstractRegistry {
@Override
public void register(URL url) {
if (!acceptable(url)) {
logger.info("URL " + url + " will not be registered to Registry. Registry " + url + " does not accept service of this protocol type.");
return;
}
super.register(url);
removeFailedRegistered(url);
removeFailedUnregistered(url);
try {
// Sending a registration request to the server side
// 模板方法,由子类实现
doRegister(url);
} catch (Exception e) {
Throwable t = e;
// If the startup detection is opened, the Exception is thrown directly.
// 获取 check 参数,若 check = true 将会直接抛出异常
boolean check = getUrl().getParameter(Constants.CHECK_KEY, true)
&& url.getParameter(Constants.CHECK_KEY, true)
&& !CONSUMER_PROTOCOL.equals(url.getProtocol());
boolean skipFailback = t instanceof SkipFailbackWrapperException;
if (check || skipFailback) {
if (skipFailback) {
t = t.getCause();
}
throw new IllegalStateException("Failed to register " + url + " to registry " + getUrl().getAddress() + ", cause: " + t.getMessage(), t);
} else {
logger.error("Failed to register " + url + ", waiting for retry, cause: " + t.getMessage(), t);
}
// Record a failed registration request to a failed list, retry regularly
// 记录注册失败的链接
addFailedRegistered(url);
}
}
}
-
进入doRegister方法,不同的注册中心有相对应的类
public class ZookeeperRegistry extends FailbackRegistry {
@Override
public void doRegister(URL url) {
try {
// 通过 Zookeeper 客户端创建节点,节点路径由 toUrlPath 方法生成,路径格式如下:
// /${group}/${serviceInterface}/providers/${url}
// 比如
// /dubbo/org.apache.dubbo.DemoService/providers/dubbo%3A%2F%2F127.0.0.1......
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);
}
}
}
- 进入create方法
public abstract class AbstractZookeeperClient<TargetDataListener, TargetChildListener> implements ZookeeperClient {
@Override
public void create(String path, boolean ephemeral) {
if (!ephemeral) {
if(persistentExistNodePath.contains(path)){
return;
}
// 如果要创建的节点类型非临时节点,那么这里要检测节点是否存在
if (checkExists(path)) {
persistentExistNodePath.add(path);
return;
}
}
int i = path.lastIndexOf('/');
if (i > 0) {
// 递归创建上一级路径
create(path.substring(0, i), false);
}
// 根据 ephemeral 的值创建临时或持久节点
if (ephemeral) {
createEphemeral(path);
} else {
createPersistent(path);
persistentExistNodePath.add(path);
}
}
}
- 进入createEphemeral
public class CuratorZookeeperClient extends AbstractZookeeperClient<CuratorZookeeperClient.CuratorWatcherImpl, CuratorZookeeperClient.CuratorWatcherImpl> {
@Override
public void createEphemeral(String path) {
try {
// 通过 Curator 框架创建节点
client.create().withMode(CreateMode.EPHEMERAL).forPath(path);
} catch (NodeExistsException e) {
logger.warn("ZNode " + path + " already exists, since we will only try to recreate a node on a session expiration" +
", this duplication might be caused by a delete delay from the zk server, which means the old expired session" +
" may still holds this ZNode and the server just hasn't got time to do the deletion. In this case, " +
"we can just try to delete and create again.", e);
deletePath(path);
createEphemeral(path);
} catch (Exception e) {
throw new IllegalStateException(e.getMessage(), e);
}
}
}
根据上面的方法,可以将当前服务对应的配置信息(存储在URL中的)注册到注册中心/dubbo/org.apache.dubbo.demo.DemoService/providers/ 。里面直接使用了Curator进行创建节点(Curator是Netflix公司开源的一套zookeeper客户端框架)。
七、总结
到这里Dubbo的服务注册流程终于是解释完。核心在于Dubbo使用规定好的URL+SPI进行寻找和发现服务,通过URL定位注册中心,再通过将服务的URL发布到注册中心从而使得消费者可以知道服务的有哪些,里面可以看见对于URL这种复杂的对象并且需要经常更改的,通常采用建造者模式。而2.7.3版本的Dubbo源码也使用了Java8以后的新特性Lambda表达式来构建隐式函数。
参考:
https://www.cnblogs.com/Cubemen/p/12294377.html
https://blog.csdn.net/weixin_38308374/article/details/105983937
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