spring cloud 服务注册源码分析-nacos

spring cloud针对服务注册和发现仅提供了抽象（都封装在spring-cloud-commons包里），常见的实现有eureka、nacos等组件，这里主要以nacos为例进行源码分析，本文代码依赖版本

spring-cloud	spring-cloud-alibaba
Hoxton.SR8	2.2.5.RELEASE

1. 服务注册的核心接口

AutoServiceRegistration

接口：服务注册配置类，spring针对该接口实现了一个抽象类

AbstractAutoServiceRegistration

是服务注册的触发类。

ServiceRegistry

接口：负责具体的服务注册

Registration

接口：主要定义服务注册所需要的一些信息，如：本服务的服务名、ip地址端口号、元数据等等。

2. 从@EnableDiscoveryClient说起

@Import(EnableDiscoveryClientImportSelector.class)
public @interface EnableDiscoveryClient {
	boolean autoRegister() default true;
}

主要引入了

EnableDiscoveryClientImportSelector

。

@Order(Ordered.LOWEST_PRECEDENCE - 100)
public class EnableDiscoveryClientImportSelector
		extends SpringFactoryImportSelector<EnableDiscoveryClient> {

	@Override
	public String[] selectImports(AnnotationMetadata metadata) {
		String[] imports = super.selectImports(metadata);

		AnnotationAttributes attributes = AnnotationAttributes.fromMap(
				metadata.getAnnotationAttributes(getAnnotationClass().getName(), true));

		boolean autoRegister = attributes.getBoolean("autoRegister");

		if (autoRegister) {
			List<String> importsList = new ArrayList<>(Arrays.asList(imports));
			importsList.add(
					"org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationConfiguration");
			imports = importsList.toArray(new String[0]);
		}
		......省略后面代码.....
}

从上面可以看到默认开启了注册功能，向spring中注册了

AutoServiceRegistrationConfiguration

类。

@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(AutoServiceRegistrationProperties.class)
@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",
		matchIfMissing = true)
public class AutoServiceRegistrationConfiguration {

}

这类啥也没，就启用了

AutoServiceRegistrationProperties

配置。

一脸懵逼…………………………

3. AutoServiceRegistrationAutoConfiguration配置类

继续寻找突破口，在spring-cloud-commons的spring.factories文件里发现EnableAutoConfiguration的参数里有AutoServiceRegistrationAutoConfiguration。

@Configuration(proxyBeanMethods = false)
@Import(AutoServiceRegistrationConfiguration.class)
@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",
		matchIfMissing = true)
public class AutoServiceRegistrationAutoConfiguration {

	@Autowired(required = false)
	private AutoServiceRegistration autoServiceRegistration;

	@Autowired
	private AutoServiceRegistrationProperties properties;

	@PostConstruct
	protected void init() {
		if (this.autoServiceRegistration == null && this.properties.isFailFast()) {
			throw new IllegalStateException("Auto Service Registration has "
					+ "been requested, but there is no AutoServiceRegistration bean");
		}
	}

}

发现注入的有

AutoServiceRegistration

接口，并在构造完成后对

AutoServiceRegistration

做了不为空的校验.

4. Nacos服务注册接口的实现

4.1. NacosAutoServiceRegistration实现类

NacosAutoServiceRegistration

继承

AbstractAutoServiceRegistration

类。

先看看

AbstractAutoServiceRegistration

类

public abstract class AbstractAutoServiceRegistration<R extends Registration>
		implements AutoServiceRegistration, ApplicationContextAware,
		ApplicationListener<WebServerInitializedEvent> {
		    public void onApplicationEvent(WebServerInitializedEvent event) {
		bind(event);//关键步骤一
	}

	@Deprecated
	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();//关键步骤二
	}
	public void start() {
	            ……………………
		// only initialize if nonSecurePort is greater than 0 and it isn't already running
		// because of containerPortInitializer below
		if (!this.running.get()) {
		 ……………………
			register();//关键步骤三
		 ……………………
		}
	}
	protected void register() {
		this.serviceRegistry.register(getRegistration());//关键步骤四
	}
}

顺着上面的关键步骤可以知道spring在web容器初始化完成后会出发服务注册的操作。接着看具体实现类

NacosAutoServiceRegistration

public class NacosAutoServiceRegistration
		extends AbstractAutoServiceRegistration<Registration> {

	private static final Logger log = LoggerFactory
			.getLogger(NacosAutoServiceRegistration.class);

	private NacosRegistration registration;

	public NacosAutoServiceRegistration(ServiceRegistry<Registration> serviceRegistry,
			AutoServiceRegistrationProperties autoServiceRegistrationProperties,
			NacosRegistration registration) {
		super(serviceRegistry, autoServiceRegistrationProperties);
		this.registration = registration;
	}
	
}

从构造方法可以看出已将serviceRegistry和registration赋值。

4.2. NacosServiceRegistry类和NacosRegistration类

NacosServiceRegistry

实现接口

ServiceRegistry

public NacosServiceRegistry(NacosDiscoveryProperties nacosDiscoveryProperties) {
		this.nacosDiscoveryProperties = nacosDiscoveryProperties;
	}

	@Override
	public void register(Registration registration) {

		if (StringUtils.isEmpty(registration.getServiceId())) {
			log.warn("No service to register for nacos client...");
			return;
		}

		NamingService namingService = namingService();
		String serviceId = registration.getServiceId();
		String group = nacosDiscoveryProperties.getGroup();

		Instance instance = getNacosInstanceFromRegistration(registration);

		try {
			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);
		}
	}

这个类实现了nacos的注册逻辑

4.3. Nacos服务注册接口实现类的创建

上面讲了Nacos服务注册接口实现类的作用，在哪创建的呢？

在

spring-cloud-starter-alibaba-nacos-discovery

包的spring.factories 里有

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

打开

NacosServiceRegistryAutoConfiguration

类

@ConditionalOnProperty(value = "spring.cloud.service-registry.auto-registration.enabled",
		matchIfMissing = true)
@AutoConfigureAfter({ AutoServiceRegistrationConfiguration.class,
		AutoServiceRegistrationAutoConfiguration.class,
		NacosDiscoveryAutoConfiguration.class })
public class NacosServiceRegistryAutoConfiguration {

	@Bean
	public NacosServiceRegistry nacosServiceRegistry(
			NacosDiscoveryProperties nacosDiscoveryProperties) {
		return new NacosServiceRegistry(nacosDiscoveryProperties);
	}

	@Bean
	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
	public NacosRegistration nacosRegistration(
			ObjectProvider<List<NacosRegistrationCustomizer>> registrationCustomizers,
			NacosDiscoveryProperties nacosDiscoveryProperties,
			ApplicationContext context) {
		return new NacosRegistration(registrationCustomizers.getIfAvailable(),
				nacosDiscoveryProperties, context);
	}

	@Bean
	@ConditionalOnBean(AutoServiceRegistrationProperties.class)
	public NacosAutoServiceRegistration nacosAutoServiceRegistration(
			NacosServiceRegistry registry,
			AutoServiceRegistrationProperties autoServiceRegistrationProperties,
			NacosRegistration registration) {
		return new NacosAutoServiceRegistration(registry,
				autoServiceRegistrationProperties, registration);
	}

}

可以看到引入该包后后，在

spring.cloud.service-registry.auto-registration.enabled

开关开启后就会自动创建

5. nacos的心跳机制（nacos-client-1.4.1）

服务注册到服务中心后，nacos注册中心维护了一个客户端的列表。

看看

BeatReactor

这个线程类：

public class BeatReactor implements Closeable {
    ……………………………………
    class BeatTask implements Runnable {
        
        BeatInfo beatInfo;
        
        public BeatTask(BeatInfo beatInfo) {
            this.beatInfo = beatInfo;
        }
        
        @Override
        public void run() {
            if (beatInfo.isStopped()) {
                return;
            }
            long nextTime = beatInfo.getPeriod();
            try {
                JsonNode result = serverProxy.sendBeat(beatInfo, BeatReactor.this.lightBeatEnabled);
                long interval = result.get("clientBeatInterval").asLong();
                boolean lightBeatEnabled = false;
                if (result.has(CommonParams.LIGHT_BEAT_ENABLED)) {
                    lightBeatEnabled = result.get(CommonParams.LIGHT_BEAT_ENABLED).asBoolean();
                }
                BeatReactor.this.lightBeatEnabled = lightBeatEnabled;
                if (interval > 0) {
                    nextTime = interval;
                }
                int code = NamingResponseCode.OK;
                if (result.has(CommonParams.CODE)) {
                    code = result.get(CommonParams.CODE).asInt();
                }
                if (code == NamingResponseCode.RESOURCE_NOT_FOUND) {
                    Instance instance = new Instance();
                    instance.setPort(beatInfo.getPort());
                    instance.setIp(beatInfo.getIp());
                    instance.setWeight(beatInfo.getWeight());
                    instance.setMetadata(beatInfo.getMetadata());
                    instance.setClusterName(beatInfo.getCluster());
                    instance.setServiceName(beatInfo.getServiceName());
                    instance.setInstanceId(instance.getInstanceId());
                    instance.setEphemeral(true);
                    try {
                        serverProxy.registerService(beatInfo.getServiceName(),
                                NamingUtils.getGroupName(beatInfo.getServiceName()), instance);
                    } catch (Exception ignore) {
                    }
                }
            } catch (NacosException ex) {
                NAMING_LOGGER.error("[CLIENT-BEAT] failed to send beat: {}, code: {}, msg: {}",
                        JacksonUtils.toJson(beatInfo), ex.getErrCode(), ex.getErrMsg());
                
            }
            executorService.schedule(new BeatTask(beatInfo), nextTime, TimeUnit.MILLISECONDS);
        }
    }
    ………………………………
}

executorService

为

ScheduledExecutorService

，定时的执行

BeatTask

这个任务，心跳的间隔时间从心跳接口中获取，当前版本为5秒一次。如果心跳接口返回没有发现该服务nacaos会再次注册服务。

spring cloud 服务注册源码分析-nacos

1. 服务注册的核心接口

2. 从@EnableDiscoveryClient说起

3. AutoServiceRegistrationAutoConfiguration配置类

4. Nacos服务注册接口的实现

4.1. NacosAutoServiceRegistration实现类

4.2. NacosServiceRegistry类和NacosRegistration类

4.3. Nacos服务注册接口实现类的创建

5. nacos的心跳机制（nacos-client-1.4.1）

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