阿里二面：使用 Nacos 做注冊中心怎么做優(yōu)雅發(fā)布？

作者：朱晉君 2023-07-18 08:28:58

無論是哪一款注冊中心，優(yōu)雅發(fā)布要解決的問題都是優(yōu)雅上線和優(yōu)雅下線。本文結(jié)合 Nacos 的原理講解了 Nacos 的優(yōu)雅發(fā)布，希望對你有所幫助。

大家好，我是君哥。今天重新發(fā)一下這篇文章。

今天來聊一聊使用 Nacos 做注冊中心怎么做優(yōu)雅發(fā)布。

跟其他的注冊中心一樣，Nacos 作為注冊中心的使用如下圖：

圖片

Service Provider 啟動(dòng)后注冊到 Nacos Server，Service Consumer 則從 Nacos Server 拉取服務(wù)列表，根據(jù)一定算法選擇一個(gè) Service Provider 來發(fā)送請求。

1.優(yōu)雅要求

對于優(yōu)雅發(fā)布，要求是 Service Provider 上線（注冊到 Nacos）后，服務(wù)能夠正常地接收和處理請求，而 Service Provider 停服后，則不會再收到請求。這就有兩個(gè)要求：

優(yōu)雅上線：Service Provider 發(fā)布完成之前，Service Consumer 不應(yīng)該從服務(wù)列表中拉取到這個(gè)服務(wù)地址；
優(yōu)雅下線：Service Provider 下線后，Service Consumer 不會從服務(wù)列表中拉取到這個(gè)服務(wù)地址。

解決了這兩個(gè)問題，優(yōu)雅發(fā)布就可以做到了。

2.搭建環(huán)境

搭建環(huán)境是為了看 Nacos 日志，通過日志找到對應(yīng)的源代碼。本文搭建的環(huán)境如下圖：

圖片

2.1 啟動(dòng) provider

啟動(dòng) springboot-provider 的應(yīng)用，注冊到 Nacos，啟動(dòng)日志如下：

2023-06-11 18:58:10,120 [main] [INFO] com.alibaba.nacos.client.naming - [BEAT] adding beat: BeatInfo{port=8083, ip='192.168.31.94', weight=1.0, serviceName='DEFAULT_GROUP@@springboot-provider', cluster='DEFAULT', metadata={management.endpoints.web.base-path=/actuator, management.port=18082, preserved.register.source=SPRING_CLOUD, management.address=127.0.0.1}, scheduled=false, period=5000, stopped=false} to beat map.
2023-06-11 18:58:10,121 [main] [INFO] com.alibaba.nacos.client.naming - [REGISTER-SERVICE] public registering service DEFAULT_GROUP@@springboot-provider with instance: Instance{instanceId='null', ip='192.168.31.94', port=8083, weight=1.0, healthy=true, enabled=true, ephemeral=true, clusterName='DEFAULT', serviceName='null', metadata={management.endpoints.web.base-path=/actuator, management.port=18082, preserved.register.source=SPRING_CLOUD, management.address=127.0.0.1}}
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.properties+DEFAULT_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=, dataId=springboot-provider.properties, group=DEFAULT_GROUP, cnt=1
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.properties+DEFAULT_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=, dataId=springboot-provider-dev.properties, group=DEFAULT_GROUP, cnt=1
2023-06-11 18:58:10,360 [main] [INFO] com.alibaba.nacos.client.config.impl.ClientWorker - [fixed-39.105.183.91_8848] [subscribe] springboot-provider+DEFAULT_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=, dataId=springboot-provider, group=DEFAULT_GROUP, cnt=1
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{port=8083, ip='192.168.31.94', weight=1.0, serviceName='DEFAULT_GROUP@@springboot-provider', cluster='DEFAULT', metadata={management.endpoints.web.base-path=/actuator, management.port=18082, preserved.register.source=SPRING_CLOUD, management.address=127.0.0.1}, scheduled=false, period=5000, stopped=false} 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_GROUP@@springboot-provider@@DEFAULT -> [{"instanceId":"192.168.31.94#8083#DEFAULT#DEFAULT_GROUP@@springboot-provider","ip":"192.168.31.94","port":8083,"weight":1.0,"healthy":true,"enabled":true,"ephemeral":true,"clusterName":"DEFAULT","serviceName":"DEFAULT_GROUP@@springboot-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_GROUP@@springboot-provider@@DEFAULT -> [{"instanceId":"192.168.31.94#8083#DEFAULT#DEFAULT_GROUP@@springboot-provider","ip":"192.168.31.94","port":8083,"weight":1.0,"healthy":true,"enabled":true,"ephemeral":true,"clusterName":"DEFAULT","serviceName":"DEFAULT_GROUP@@springboot-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}]

我們再看下 Nacos 的日志，這里看的文件 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{namespace='public', group='DEFAULT_GROUP', name='springboot-provider', ephemeral=true, revisinotallow=1}, 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 subscribers

springboot-provider 啟動(dòng)成功后，從Nacos 管理后臺可以看到下圖：

圖片

2.2 provider 下線

服務(wù)下線后，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{namespace='public', group='DEFAULT_GROUP', name='springboot-provider', ephemeral=true, revisinotallow=2}, 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_GROUP@@springboot-provider"},"lastHeartBeatTime":1686481231604,"metadataId":"192.168.31.94:8083:DEFAULT"}
2023-06-11 19:01:05,048 INFO Client remove for service Service{namespace='public', group='DEFAULT_GROUP', name='springboot-provider', ephemeral=true, revisinotallow=2}, 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 subscribers

2.3 服務(wù)調(diào)用

在 springboot-consumer 上跑一個(gè)單元測試的用例，用 FeignClient 調(diào)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 [DefaultTestContext@5bf0d49 testClass = TestFeignAsEurekaClient, testInstance = boot.service.TestFeignAsEurekaClient@10683d9d, testMethod = testPostEmployByFeign@TestFeignAsEurekaClient, testException = [null], mergedContextConfiguration = [WebMergedContextConfiguration@5b7a5baa testClass = TestFeignAsEurekaClient, locations = '{}', classes = '{class boot.Application, class boot.Application}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestCnotallow=true, server.port=0}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@166fa74d, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@588df31b, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@7fad8c79, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@10b48321], 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.DataSourceTransactionManager@693676d]; 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:name=springboot-provider,current list of Servers=[],Load balancer stats=Zone 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:name=springboot-provider,current list of Servers=[192.168.31.94:8083],Load balancer stats=Zone 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.NacosServerList@24d998ba

注意，這里使用了 OpenFeign，其中用到了 Ribbon 做負(fù)載均衡，那就需要考慮到 Ribbon 刷新本地服務(wù)列表的時(shí)間，從源代碼中看，刷新周期是 30s。如下圖：

圖片

Ribbon 刷新緩存的邏輯參考下面代碼：

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,//這里定義的是30s
    TimeUnit.MILLISECONDS
  );
 }//...
}

3.優(yōu)雅發(fā)布

前面第一節(jié)提到過，優(yōu)雅發(fā)布有兩個(gè)要求：優(yōu)雅上線和優(yōu)雅下線。

Service Consumer 初始化時(shí)會從 Nacos Server 獲取服務(wù)列表并更新本地緩存，同時(shí)會向 Nacos Server 訂閱服務(wù)列表（如果 Nacos Server 上的服務(wù)列表發(fā)生變化，會主動(dòng)通知 Service Consumer）。之后會定時(shí)（默認(rèn)間隔 1s ）拉取服務(wù)列表并更新本地緩存。代碼如下：

//NacosNamingService 類
public List<Instance> selectInstances(String serviceName, String groupName, List<String> 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);
}

在訂閱的代碼中，加入了定時(shí)更新服務(wù)列表的代碼，如下：

//NamingClientProxyDelegate 類
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 會定時(shí)（每隔 5s）檢查 Service Provider 是否健康（根據(jù)心跳來檢查），如果 15s （默認(rèn)，可以配置）沒有收到心跳，則會把服務(wù)置為不健康，并且通知 Service Consumer。代碼如下：

//UnhealthyInstanceChecker 類
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 優(yōu)雅上線

優(yōu)雅上線存在的問題主要在于 Service Provider 注冊到 Nacos 后，服務(wù)還沒有完成初始化，請求已經(jīng)到來。這種情況主要原因是 Service Provider 啟動(dòng)后立刻注冊 Naocs，而本身提供的接口可能還沒有初始化完成。

這種情況的解決方法是關(guān)閉自動(dòng)注冊：

spring.cloud.nacos.discovery.registerEnabled=false

在服務(wù)初始化后使用代碼手動(dòng)注冊，代碼如下：

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 優(yōu)雅下線

對于正常下線，Nacos Server 收到 Provider 發(fā)送的下線請求后，會通知訂閱的 Server Consumer，而且 Consumer 也會每隔 1s 去更新本地服務(wù)列表，這個(gè)過程已經(jīng)非常接近優(yōu)雅下線了。

而對于異常下線，Nacos Server 采用心跳檢測機(jī)制來更新服務(wù)列表。心跳周期是 5s，Nacos Server 如果 15s 沒收到心跳就才會將實(shí)例設(shè)置為不健康。

3.2.1 正常停服

正常下線的情況下，最優(yōu)雅的方式是先向 Nacos Server 發(fā)送下線通知，發(fā)送通知一段時(shí)間（比如 5s）后，再停服。比如增加一個(gè) API 接口，服務(wù)下線之前增加 preStopHook 函數(shù)調(diào)用這個(gè) API 接口來實(shí)現(xiàn)下線。API 接口示例代碼如下：

@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 的場景，也需要考慮 Ribbon 更新本地緩存服務(wù)列表的機(jī)制，手動(dòng)下線后，可以再等待 30s 后關(guān)閉服務(wù)。

3.2.1 服務(wù)故障

對于服務(wù)故障的情況，Nacos Server 需要采用心跳來檢測服務(wù)在線，如果 15s 沒收到心跳才會將實(shí)例設(shè)置為不健康，在 30s 沒收到心跳才會把這個(gè)服務(wù)從列表中刪除。這個(gè)時(shí)間可以做優(yōu)化設(shè)置：

spring.cloud.nacos.discovery.metadata.preserved.heart.beat.interval=1000 #心跳間隔5s->1s
spring.cloud.nacos.discovery.metadata.preserved.heart.beat.timeout=3000 #超時(shí)時(shí)間15s->3s
spring.cloud.nacos.discovery.metadata.preserved.ip.delete.timeout=5000 #刪除時(shí)間30s->5s

但是，Service Provider 故障情況下，即使做優(yōu)化配置，也是很難讓 Service Consumer 無感知。

極端情況下，可能 Provider 部分服務(wù)已經(jīng)不能正常提供了，但還是會向 Nacos Server 發(fā)送心跳，這種情況可以采用服務(wù)本身的健康檢查來通知 Nacos Server 服務(wù)下線。