阿里二面：使用 Nacos 做注册中心怎么做优雅发布？-北京尧图网络

今天来聊一聊使用 Nacos 做注册中心怎么做优雅发布。跟其他的注册中心一样Nacos 作为注册中心的使用如下图Service Provider 启动后注册到 Nacos ServerService Consumer 则从 Nacos Server 拉取服务列表根据一定算法选择一个 Service Provider 来发送请求。1.优雅要求对于优雅发布要求是 Service Provider 上线注册到 Nacos后服务能够正常地接收和处理请求而 Service Provider 停服后则不会再收到请求。这就有两个要求优雅上线Service Provider 发布完成之前Service Consumer 不应该从服务列表中拉取到这个服务地址优雅下线Service Provider 下线后Service Consumer 不会从服务列表中拉取到这个服务地址。解决了这两个问题优雅发布就可以做到了。2.搭建环境搭建环境是为了看 Nacos 日志通过日志找到对应的源代码。本文搭建的环境如下图2.1 启动 provider启动 springboot-provider 的应用注册到 Nacos启动日志如下2023-06-11 18:58:10,120 [main] [INFO] com.alibaba.nacos.client.naming - [BEAT] adding beat: BeatInfo{port8083, ip192.168.31.94, weight1.0, serviceNameDEFAULT_GROUPspringboot-provider, clusterDEFAULT, metadata{management.endpoints.web.base-path/actuator, management.port18082, preserved.register.sourceSPRING_CLOUD, management.address127.0.0.1}, scheduledfalse, period5000, stoppedfalse} to beat map. 2023-06-11 18:58:10,121 [main] [INFO] com.alibaba.nacos.client.naming - [REGISTER-SERVICE] public registering service DEFAULT_GROUPspringboot-provider with instance: Instance{instanceIdnull, ip192.168.31.94, port8083, weight1.0, healthytrue, enabledtrue, ephemeraltrue, clusterNameDEFAULT, serviceNamenull, metadata{management.endpoints.web.base-path/actuator, management.port18082, preserved.register.sourceSPRING_CLOUD, management.address127.0.0.1}} 2023-06-11 18:58:10,133 [main] [INFO] com.alibaba.cloud.nacos.registry.NacosServiceRegistry - nacos registry, DEFAULT_GROUP springboot-provider 192.168.31.94:8083 register finished 2023-06-11 18:58:10,221 [main] [INFO] org.springframework.boot.web.embedded.tomcat.TomcatWebServer - Tomcat initialized with port(s): 18082 (http) 2023-06-11 18:58:10,222 [main] [INFO] org.apache.coyote.http11.Http11NioProtocol - Initializing ProtocolHandler [http-nio-127.0.0.1-18082] 2023-06-11 18:58:10,223 [main] [INFO] org.apache.catalina.core.StandardService - Starting service [Tomcat] 2023-06-11 18:58:10,223 [main] [INFO] org.apache.catalina.core.StandardEngine - Starting Servlet engine: [Apache Tomcat/9.0.21] 2023-06-11 18:58:10,239 [main] [INFO] org.apache.catalina.core.ContainerBase.[Tomcat-1].[localhost].[/] - Initializing Spring embedded WebApplicationContext 2023-06-11 18:58:10,239 [main] [INFO] org.springframework.web.context.ContextLoader - Root WebApplicationContext: initialization completed in 99 ms 2023-06-11 18:58:10,268 [main] [INFO] org.springframework.boot.actuate.endpoint.web.EndpointLinksResolver - Exposing 22 endpoint(s) beneath base path /actuator 2023-06-11 18:58:10,336 [main] [INFO] org.apache.coyote.http11.Http11NioProtocol - Starting ProtocolHandler [http-nio-127.0.0.1-18082] 2023-06-11 18:58:10,340 [main] [INFO] org.springframework.boot.web.embedded.tomcat.TomcatWebServer - Tomcat started on port(s): 18082 (http) with context path 2023-06-11 18:58:10,342 [main] [INFO] boot.Application - Started Application in 7.051 seconds (JVM running for 7.874) 2023-06-11 18:58:10,358 [main] [INFO] com.alibaba.nacos.client.config.impl.ClientWorker - [fixed-39.105.183.91_8848] [subscribe] springboot-provider.propertiesDEFAULT_GROUP 2023-06-11 18:58:10,359 [main] [INFO] com.alibaba.nacos.client.config.impl.CacheData - [fixed-39.105.183.91_8848] [add-listener] ok, tenant, dataIdspringboot-provider.properties, groupDEFAULT_GROUP, cnt1 2023-06-11 18:58:10,359 [main] [INFO] com.alibaba.nacos.client.config.impl.ClientWorker - [fixed-39.105.183.91_8848] [subscribe] springboot-provider-dev.propertiesDEFAULT_GROUP 2023-06-11 18:58:10,359 [main] [INFO] com.alibaba.nacos.client.config.impl.CacheData - [fixed-39.105.183.91_8848] [add-listener] ok, tenant, dataIdspringboot-provider-dev.properties, groupDEFAULT_GROUP, cnt1 2023-06-11 18:58:10,360 [main] [INFO] com.alibaba.nacos.client.config.impl.ClientWorker - [fixed-39.105.183.91_8848] [subscribe] springboot-providerDEFAULT_GROUP 2023-06-11 18:58:10,360 [main] [INFO] com.alibaba.nacos.client.config.impl.CacheData - [fixed-39.105.183.91_8848] [add-listener] ok, tenant, dataIdspringboot-provider, groupDEFAULT_GROUP, cnt1 2023-06-11 18:58:10,639 [RMI TCP Connection(1)-192.168.31.94] [INFO] org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/] - Initializing Spring DispatcherServlet dispatcherServlet 2023-06-11 18:58:10,839 [com.alibaba.nacos.client.naming.updater] [INFO] com.alibaba.nacos.client.naming - [BEAT] adding beat: BeatInfo{port8083, ip192.168.31.94, weight1.0, serviceNameDEFAULT_GROUPspringboot-provider, clusterDEFAULT, metadata{management.endpoints.web.base-path/actuator, management.port18082, preserved.register.sourceSPRING_CLOUD, management.address127.0.0.1}, scheduledfalse, period5000, stoppedfalse} to beat map. 2023-06-11 18:58:10,840 [com.alibaba.nacos.client.naming.updater] [INFO] com.alibaba.nacos.client.naming - modified ips(1) service: DEFAULT_GROUPspringboot-providerDEFAULT - [{instanceId:192.168.31.94#8083#DEFAULT#DEFAULT_GROUPspringboot-provider,ip:192.168.31.94,port:8083,weight:1.0,healthy:true,enabled:true,ephemeral:true,clusterName:DEFAULT,serviceName:DEFAULT_GROUPspringboot-provider,metadata:{management.endpoints.web.base-path:/actuator,management.port:18082,preserved.register.source:SPRING_CLOUD,management.address:127.0.0.1},ipDeleteTimeout:30000,instanceHeartBeatInterval:5000,instanceHeartBeatTimeOut:15000}] 2023-06-11 18:58:10,841 [com.alibaba.nacos.client.naming.updater] [INFO] com.alibaba.nacos.client.naming - current ips:(1) service: DEFAULT_GROUPspringboot-providerDEFAULT - [{instanceId:192.168.31.94#8083#DEFAULT#DEFAULT_GROUPspringboot-provider,ip:192.168.31.94,port:8083,weight:1.0,healthy:true,enabled:true,ephemeral:true,clusterName:DEFAULT,serviceName:DEFAULT_GROUPspringboot-provider,metadata:{management.endpoints.web.base-path:/actuator,management.port:18082,preserved.register.source:SPRING_CLOUD,management.address:127.0.0.1},ipDeleteTimeout:30000,instanceHeartBeatInterval:5000,instanceHeartBeatTimeOut:15000}]我们再看下 Nacos 的日志这里看的文件 naming-server.log日志如下2023-06-11 18:58:09,723 INFO Client connection 192.168.31.94:51885#true connect 2023-06-11 18:58:10,105 INFO Client change for service Service{namespacepublic, groupDEFAULT_GROUP, namespringboot-provider, ephemeraltrue, revision1}, 192.168.31.94:8083#true 2023-06-11 18:58:18,204 INFO Client connection 192.168.31.94:60850#true disconnect, remove instances and subscribersspringboot-provider 启动成功后从Nacos 管理后台可以看到下图2.2 provider 下线服务下线后Nacos 日志如下2023-06-11 19:01:03,375 INFO Client connection 192.168.31.94:51885#true disconnect, remove instances and subscribers 2023-06-11 19:01:05,048 INFO [AUTO-DELETE-IP] service: Service{namespacepublic, groupDEFAULT_GROUP, namespringboot-provider, ephemeraltrue, revision2}, ip: {ip:192.168.31.94,port:8083,healthy:false,cluster:DEFAULT,extendDatum:{management.endpoints.web.base-path:/actuator,management.port:18082,preserved.register.source:SPRING_CLOUD,management.address:127.0.0.1,customInstanceId:192.168.31.94#8083#DEFAULT#DEFAULT_GROUPspringboot-provider},lastHeartBeatTime:1686481231604,metadataId:192.168.31.94:8083:DEFAULT} 2023-06-11 19:01:05,048 INFO Client remove for service Service{namespacepublic, groupDEFAULT_GROUP, namespringboot-provider, ephemeraltrue, revision2}, 192.168.31.94:8083#true 2023-06-11 19:01:08,379 INFO Client connection 192.168.31.94:8083#true disconnect, remove instances and subscribers2.3 服务调用在 springboot-consumer 上跑一个单元测试的用例用 FeignClient 调用下面的方法FeignClient(value springboot-provider, configuration FeignMultipartSupportConfig.class) public interface FeignAsEurekaClient { PostMapping(/employee/save) String saveEmployeebyName(RequestBody Employee employee); }日志如下2023-06-11 19:15:47,694 [main] [INFO] org.springframework.test.context.transaction.TransactionContext - Began transaction (1) for test context [DefaultTestContext5bf0d49 testClass TestFeignAsEurekaClient, testInstance boot.service.TestFeignAsEurekaClient10683d9d, testMethod testPostEmployByFeignTestFeignAsEurekaClient, testException [null], mergedContextConfiguration [WebMergedContextConfiguration5b7a5baa testClass TestFeignAsEurekaClient, locations {}, classes {class boot.Application, class boot.Application}, contextInitializerClasses [], activeProfiles {}, propertySourceLocations {}, propertySourceProperties {org.springframework.boot.test.context.SpringBootTestContextBootstrappertrue, server.port0}, contextCustomizers set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer166fa74d, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer588df31b, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer7fad8c79, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer10b48321], resourceBasePath src/main/webapp, contextLoader org.springframework.boot.test.context.SpringBootContextLoader, parent [null]], attributes map[org.springframework.test.context.web.ServletTestExecutionListener.activateListener - false]]; transaction manager [org.springframework.jdbc.datasource.DataSourceTransactionManager693676d]; rollback [true] 2023-06-11 19:15:47,941 [main] [INFO] com.netflix.config.ChainedDynamicProperty - Flipping property: springboot-provider.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit 2147483647 2023-06-11 19:15:47,962 [main] [INFO] com.netflix.loadbalancer.BaseLoadBalancer - Client: springboot-provider instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:namespringboot-provider,current list of Servers[],Load balancer statsZone stats: {},Server stats: []}ServerList:null 2023-06-11 19:15:47,969 [main] [INFO] com.netflix.loadbalancer.DynamicServerListLoadBalancer - Using serverListUpdater PollingServerListUpdater 2023-06-11 19:15:48,064 [main] [INFO] com.netflix.config.ChainedDynamicProperty - Flipping property: springboot-provider.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit 2147483647 2023-06-11 19:15:48,064 [main] [INFO] com.netflix.loadbalancer.DynamicServerListLoadBalancer - DynamicServerListLoadBalancer for client springboot-provider initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:namespringboot-provider,current list of Servers[192.168.31.94:8083],Load balancer statsZone stats: {unknown[Zone:unknown; Instance count:1; Active connections count: 0; Circuit breaker tripped count: 0; Active connections per server: 0.0;] },Server stats: [[Server:192.168.31.94:8083; Zone:UNKNOWN; Total Requests:0; Successive connection failure:0; Total blackout seconds:0; Last connection made:Thu Jan 01 08:00:00 CST 1970; First connection made: Thu Jan 01 08:00:00 CST 1970; Active Connections:0; total failure count in last (1000) msecs:0; average resp time:0.0; 90 percentile resp time:0.0; 95 percentile resp time:0.0; min resp time:0.0; max resp time:0.0; stddev resp time:0.0] ]}ServerList:com.alibaba.cloud.nacos.ribbon.NacosServerList24d998ba注意这里使用了 OpenFeign其中用到了 Ribbon 做负载均衡那就需要考虑到 Ribbon 刷新本地服务列表的时间从源代码中看刷新周期是 30s。如下图Ribbon 刷新缓存的逻辑参考下面代码public synchronized void start(final UpdateAction updateAction) { if (isActive.compareAndSet(false, true)) { final Runnable wrapperRunnable new Runnable() { Override public void run() { //... } }; scheduledFuture getRefreshExecutor().scheduleWithFixedDelay( wrapperRunnable, initialDelayMs, refreshIntervalMs,//这里定义的是30s TimeUnit.MILLISECONDS ); }//... }3.优雅发布前面第一节提到过优雅发布有两个要求优雅上线和优雅下线。Service Consumer 初始化时会从 Nacos Server 获取服务列表并更新本地缓存同时会向 Nacos Server 订阅服务列表如果 Nacos Server 上的服务列表发生变化会主动通知 Service Consumer。之后会定时默认间隔 1s 拉取服务列表并更新本地缓存。代码如下//NacosNamingService 类 public ListInstance selectInstances(String serviceName, String groupName, ListString clusters, boolean healthy, boolean subscribe) throws NacosException { ServiceInfo serviceInfo; String clusterString StringUtils.join(clusters, ,); if (subscribe) { serviceInfo serviceInfoHolder.getServiceInfo(serviceName, groupName, clusterString); if (null serviceInfo) { serviceInfo clientProxy.subscribe(serviceName, groupName, clusterString); } } else { serviceInfo clientProxy.queryInstancesOfService(serviceName, groupName, clusterString, 0, false); } return selectInstances(serviceInfo, healthy); }在订阅的代码中加入了定时更新服务列表的代码如下//NamingClientProxyDelegate 类 public ServiceInfo subscribe(String serviceName, String groupName, String clusters) throws NacosException { NAMING_LOGGER.info([SUBSCRIBE-SERVICE] service:{}, group:{}, clusters:{} , serviceName, groupName, clusters); String serviceNameWithGroup NamingUtils.getGroupedName(serviceName, groupName); String serviceKey ServiceInfo.getKey(serviceNameWithGroup, clusters); serviceInfoUpdateService.scheduleUpdateIfAbsent(serviceName, groupName, clusters); ServiceInfo result serviceInfoHolder.getServiceInfoMap().get(serviceKey); if (null result || !isSubscribed(serviceName, groupName, clusters)) { result grpcClientProxy.subscribe(serviceName, groupName, clusters); } serviceInfoHolder.processServiceInfo(result); return result; }Nacos Server 会定时每隔 5s检查 Service Provider 是否健康根据心跳来检查如果 15s 默认可以配置没有收到心跳则会把服务置为不健康并且通知 Service Consumer。代码如下//UnhealthyInstanceChecker 类 public void doCheck(Client client, Service service, HealthCheckInstancePublishInfo instance) { if (instance.isHealthy() isUnhealthy(service, instance)) { changeHealthyStatus(client, service, instance); } } private void changeHealthyStatus(Client client, Service service, HealthCheckInstancePublishInfo instance) { instance.setHealthy(false); NotifyCenter.publishEvent(new ServiceEvent.ServiceChangedEvent(service)); NotifyCenter.publishEvent(new ClientEvent.ClientChangedEvent(client)); NotifyCenter.publishEvent(new HealthStateChangeTraceEvent(System.currentTimeMillis(), service.getNamespace(), service.getGroup(), service.getName(), instance.getIp(), instance.getPort(), false, client_beat)); }3.1 优雅上线优雅上线存在的问题主要在于 Service Provider 注册到 Nacos 后服务还没有完成初始化请求已经到来。这种情况主要原因是 Service Provider 启动后立刻注册 Naocs而本身提供的接口可能还没有初始化完成。这种情况的解决方法是关闭自动注册spring.cloud.nacos.discovery.registerEnabledfalse在服务初始化后使用代码手动注册代码如下Properties setting8 new Properties(); String serverIp8 127.0.0.1:8848; setting8.put(PropertyKeyConst.SERVER_ADDR, serverIp8); setting8.put(PropertyKeyConst.USERNAME, nacos); setting8.put(PropertyKeyConst.PASSWORD, nacos); NamingService inaming8 NacosFactory.createNamingService(setting7); inaming8.registerInstance(springboot-provider, 192.168.31.94, 8083);3.2 优雅下线对于正常下线Nacos Server 收到 Provider 发送的下线请求后会通知订阅的 Server Consumer而且 Consumer 也会每隔 1s 去更新本地服务列表这个过程已经非常接近优雅下线了。而对于异常下线Nacos Server 采用心跳检测机制来更新服务列表。心跳周期是 5sNacos Server 如果 15s 没收到心跳就才会将实例设置为不健康。3.2.1 正常停服正常下线的情况下最优雅的方式是先向 Nacos Server 发送下线通知发送通知一段时间比如 5s后再停服。比如增加一个 API 接口服务下线之前增加 preStopHook 函数调用这个 API 接口来实现下线。API 接口示例代码如下GetMapping(value /nacos/deregisterInstance) public String deregisterInstance() { Properties prop new Properties(); prop.setProperty(serverAddr, localhost); prop.put(PropertyKeyConst.NAMESPACE, test); NacosNamingService client new NacosNamingService(prop); client.deregisterInstance(springboot-provider, 192.168.31.94, 8083); return success; }在使用 Ribbon 的场景也需要考虑 Ribbon 更新本地缓存服务列表的机制手动下线后可以再等待 30s 后关闭服务。3.2.1 服务故障对于服务故障的情况Nacos Server 需要采用心跳来检测服务在线如果 15s 没收到心跳才会将实例设置为不健康在 30s 没收到心跳才会把这个服务从列表中删除。这个时间可以做优化设置spring.cloud.nacos.discovery.metadata.preserved.heart.beat.interval1000 #心跳间隔5s-1s spring.cloud.nacos.discovery.metadata.preserved.heart.beat.timeout3000 #超时时间15s-3s spring.cloud.nacos.discovery.metadata.preserved.ip.delete.timeout5000 #删除时间30s-5s但是Service Provider 故障情况下即使做优化配置也是很难让 Service Consumer 无感知。极端情况下可能 Provider 部分服务已经不能正常提供了但还是会向 Nacos Server 发送心跳这种情况可以采用服务本身的健康检查来通知 Nacos Server 服务下线。4 总结无论是哪一款注册中心优雅发布要解决的问题都是优雅上线和优雅下线。本文结合 Nacos 的原理讲解了 Nacos 的优雅发布希望对你有所帮助。2026年最新版百万八股面试宝典《Java》《大模型》《大并发》《大数据》本题库由资深讲师联合大厂面试官精心打造专为高级IT岗位设计【220万字八股文面试宝典领取】面试突击体系相关Java企业架构体系相关AI大模型相关HR 面试软技能设计模式相关并发编程相关网络IO与Netty相关互联网三高项目相关亿级流量多级缓存相关数据结构算法相关分布式相关分布式锁相关分布式ID相关核心源码相关大厂线上故障分析相关Docker相关Dubbo相关ElasticSearch相关GoLang相关Java基础核心JVM核心相关JVM调优底层相关Kafka相关Kubernetes相关Linux相关MongoDB相关MQ相关MySQL相关MyBatis相关MyBatisPlus相关Postgresql相关RabbitMQ相关RocketMQ相关Redis相关ShardingSphere相关Shiro相关SkyWalking相关Solr相关Spring 相关SpringBoot相关SpringCloud相关SpringMVC源码相关SpringSecurity相关Spring WebFlux相关领域驱动设计DDD相关任务调度Airflow相关Zookeeper相关HDFS面试题MapReduce面试题Yarn面试题Hive相关SQL面试题相关Scala面试题Spark面试题Flink相关Doris相关Tomcat源码相关网络安全相关运维/云原生相关

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