环境介绍:
Jdk 1.8
nacos-server-1.4.2
spring-boot-2.3.5.RELEASE
spring-cloud-Hoxton.SR8
spring-cloiud-alibab-2.2.5.RELEASE
Nacos 服务架构
以 Spring-Boot 为服务基础搭建平台, Nacos 在服务架构中的位置如下图所示:
总的来说和 Nacos 功能类似的中间件有 Eureka、Zookeeper、Consul 、Etcd 等。
Nacos 最大的特点就是既能够支持 AP、也能够支持 CP 模式,在分区一致性方面使用的是 Raft 协议来实现。
Nacos 客户端
我们以 spring-cloud-starter-alibaba-nacos-discovery
依赖为例
<dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId> </dependency>
它是一个标准的 spring-cloud 插件,我们首先就可以看 spring.factories
这个文
件,来找到它的启动配置类信息
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.alibaba.cloud.nacos.discovery.NacosDiscoveryAutoConfiguration,\ com.alibaba.cloud.nacos.ribbon.RibbonNacosAutoConfiguration,\ com.alibaba.cloud.nacos.endpoint.NacosDiscoveryEndpointAutoConfiguration,\ com.alibaba.cloud.nacos.registry.NacosServiceRegistryAutoConfiguration,\ com.alibaba.cloud.nacos.discovery.NacosDiscoveryClientConfiguration,\ com.alibaba.cloud.nacos.discovery.reactive.NacosReactiveDiscoveryClientConfiguration,\ com.alibaba.cloud.nacos.discovery.configclient.NacosConfigServerAutoConfiguration,\ com.alibaba.cloud.nacos.NacosServiceAutoConfiguration org.springframework.cloud.bootstrap.BootstrapConfiguration=\ com.alibaba.cloud.nacos.discovery.configclient.NacosDiscoveryClientConfigServiceBootstrapConfiguration
我们通常都是查看 “中间件名” + AutoConfiguration
开头的类, 由此我可以定位到 NacosDiscoveryAutoConfiguration
作为我们优先查看的类。
服务注册客户端
添加依赖
Nacos 服务注册是客户端主动发起,在 Spring 启动的过程中利用 Spring 提供的拓展方法来完成注册。首先我们需要导入spring-cloud-starter-alibaba-nacos-discovery
依赖
<dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId> </dependency>
分析源码
对于 spring-boot 组件我们首先先找它的 META-INF/spring.factories
文件
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.alibaba.cloud.nacos.discovery.NacosDiscoveryAutoConfiguration,\ com.alibaba.cloud.nacos.ribbon.RibbonNacosAutoConfiguration,\ com.alibaba.cloud.nacos.endpoint.NacosDiscoveryEndpointAutoConfiguration,\ com.alibaba.cloud.nacos.registry.NacosServiceRegistryAutoConfiguration,\ com.alibaba.cloud.nacos.discovery.NacosDiscoveryClientConfiguration,\ com.alibaba.cloud.nacos.discovery.reactive.NacosReactiveDiscoveryClientConfiguration,\ com.alibaba.cloud.nacos.discovery.configclient.NacosConfigServerAutoConfiguration,\ com.alibaba.cloud.nacos.NacosServiceAutoConfiguration org.springframework.cloud.bootstrap.BootstrapConfiguration=\ com.alibaba.cloud.nacos.discovery.configclient.NacosDiscoveryClientConfigServiceBootstrapConfiguration
通过我的分析发现 NacosServiceRegistryAutoConfiguration
是咱们服务注册的核心配置类,该类中定义了三个核心的 Bean 对象:
NacosServiceRegistry
NacosRegistration
NacosAutoServiceRegistration
NacosAutoServiceRegistration
NacosAutoServiceRegistration
实现了服务向 Nacos 发起注册的功能,它继承自抽象类 AbstractAutoServiceRegistration
。
在抽象类 AbstractAutoServiceRegistration
中实现 ApplicationContextAware
、ApplicationListener<WebServerInitializedEvent>
接口。在容器启动、并且上下文准备就绪过后会调用 onApplicationEvent
方法
public void onApplicationEvent(WebServerInitializedEvent event) { bind(event); }
实际调用 bind(event)
方法
public void bind(WebServerInitializedEvent event) { ApplicationContext context = event.getApplicationContext(); if (context instanceof ConfigurableWebServerApplicationContext) { if ("management".equals(((ConfigurableWebServerApplicationContext) context) .getServerNamespace())) { return; } } this.port.compareAndSet(0, event.getWebServer().getPort()); this.start(); }
然后调用 start()
方法
public void start() { if (!isEnabled()) { if (logger.isDebugEnabled()) { logger.debug("Discovery Lifecycle disabled. Not starting"); } return; } // only initialize if nonSecurePort is greater than 0 and it isn't already running // because of containerPortInitializer below if (!this.running.get()) { this.context.publishEvent( new InstancePreRegisteredEvent(this, getRegistration())); register(); if (shouldRegisterManagement()) { registerManagement(); } this.context.publishEvent( new InstanceRegisteredEvent<>(this, getConfiguration())); this.running.compareAndSet(false, true); } }
最后调用 register();
在内部去调用 serviceRegistry.register()
方法完成服务注册。
private final ServiceRegistry<R> serviceRegistry; protected void register() { this.serviceRegistry.register(getRegistration()); }
NacosServiceRegistry
NacosServiceRegistry
类主要的目的就是
public void register(Registration registration) { if (StringUtils.isEmpty(registration.getServiceId())) { log.warn("No service to register for nacos client..."); return; } // 默认情况下,会通过反射返回一个 `com.alibaba.nacos.client.naming.NacosNamingService` 的实例 NamingService namingService = namingService(); // 获取 serviceId , 默认使用配置: spring.application.name String serviceId = registration.getServiceId(); // 获取 group , 默认 DEFAULT_GROUP String group = nacosDiscoveryProperties.getGroup(); // 创建 instance 实例 Instance instance = getNacosInstanceFromRegistration(registration); try { // 注册实例 namingService.registerInstance(serviceId, group, instance); log.info("nacos registry, {} {} {}:{} register finished", group, serviceId, instance.getIp(), instance.getPort()); } catch (Exception e) { log.error("nacos registry, {} register failed...{},", serviceId, registration.toString(), e); // rethrow a RuntimeException if the registration is failed. // issue : https://github.com/alibaba/spring-cloud-alibaba/issues/1132 rethrowRuntimeException(e); } }
我们可以看到最后调用的是 namingService.registerInstance(serviceId, group, instance);
方法。
public void registerInstance(String serviceName, String groupName, Instance instance) throws NacosException { NamingUtils.checkInstanceIsLegal(instance); String groupedServiceName = NamingUtils.getGroupedName(serviceName, groupName); if (instance.isEphemeral()) { BeatInfo beatInfo = beatReactor.buildBeatInfo(groupedServiceName, instance); beatReactor.addBeatInfo(groupedServiceName, beatInfo); } serverProxy.registerService(groupedServiceName, groupName, instance); }
然后再调用 serverProxy.registerService(groupedServiceName, groupName, instance);
方法进行服务注册,通过 beatReactor.addBeatinfo()
创建 schedule
每间隔 5s 向服务端发送一次心跳数据