The overall problem is to use gateway As a gateway , After the service goes offline . The gateway will still forward to the offline server . This article solves the problem at the end of the service , Another article :spring cloud gateway+nacos Service offline perception delay , The request is still forwarded to the offline service It solves the problem of gateway .

1. Scene description

It's not clear whether it's the version problem or the configuration . Just record this problem .

nacos client ：1.4.1
web The server ：undertow edition 2.2.3.Final

After the service stops ,nacos The management side view service did not log off in time .
web The server is switched to tomcat, Service offline and normal logout .
Probably because nacos One required to perform logout bean It has been destroyed first . Causes logout to fail . The console has an error message

2022-04-25 11:48:39.431 ERROR 21336 --- [extShutdownHook] c.a.cloud.nacos.discovery.NacosWatch     : namingService unsubscribe failed, properties:NacosDiscoveryProperties{serverAddr='localhost:8848', endpoint='', namespace='dong-dev', watchDelay=30000, logName='', service='dong-sys-server-biz', weight=1.0, clusterName='DEFAULT', group='DEFAULT_GROUP', namingLoadCacheAtStart='false', metadata={dubbo.metadata-service.urls=[ "dubbo://10.47.17.177:20880/com.alibaba.cloud.dubbo.service.DubboMetadataService?anyhost=true&application=dong-sys-server-biz&bind.ip=10.47.17.177&bind.port=20880&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&group=dong-sys-server-biz&interface=com.alibaba.cloud.dubbo.service.DubboMetadataService&methods=getAllServiceKeys,getServiceRestMetadata,getExportedURLs,getAllExportedURLs&pid=21336&qos.enable=false&release=2.7.14&revision=2.2.7.RELEASE&service.name=ServiceBean:dong-sys-server-biz/com.alibaba.cloud.dubbo.service.DubboMetadataService:1.0.0&side=provider&timeout=13000&timestamp=1650858511190&version=1.0.0" ], dubbo.metadata.revision=0, preserved.register.source=SPRING_CLOUD, S-Version=10.47.17.177}, registerEnabled=true, ip='10.47.17.177', networkInterface='', port=8082, secure=false, accessKey='', secretKey='', heartBeatInterval=null, heartBeatTimeout=null, ipDeleteTimeout=null}

java.lang.NullPointerException: null
	at io.undertow.servlet.spec.ServletContextImpl.getInitParameterNames(ServletContextImpl.java:430) ~[undertow-servlet-2.2.3.Final.jar:2.2.3.Final]
	at org.springframework.web.context.support.ServletContextPropertySource.getPropertyNames(ServletContextPropertySource.java:41) ~[spring-web-5.3.3.jar:5.3.3]
	at com.alibaba.spring.util.PropertySourcesUtils.getPropertyNames(PropertySourcesUtils.java:130) ~[spring-context-support-1.0.11.jar:na]
	at com.alibaba.spring.util.PropertySourcesUtils.getSubProperties(PropertySourcesUtils.java:103) ~[spring-context-support-1.0.11.jar:na]
	at com.alibaba.spring.util.PropertySourcesUtils.getSubProperties(PropertySourcesUtils.java:57) ~[spring-context-support-1.0.11.jar:na]
	at com.alibaba.cloud.nacos.NacosDiscoveryProperties.enrichNacosDiscoveryProperties(NacosDiscoveryProperties.java:616) ~[spring-cloud-starter-alibaba-nacos-discovery-2021.1.jar:2021.1]
	at com.alibaba.cloud.nacos.NacosDiscoveryProperties.getNacosProperties(NacosDiscoveryProperties.java:610) ~[spring-cloud-starter-alibaba-nacos-discovery-2021.1.jar:2021.1]
	at com.alibaba.cloud.nacos.discovery.NacosWatch.stop(NacosWatch.java:165) [spring-cloud-starter-alibaba-nacos-discovery-2021.1.jar:2021.1]
	at com.alibaba.cloud.nacos.discovery.NacosWatch.stop(NacosWatch.java:97) [spring-cloud-starter-alibaba-nacos-discovery-2021.1.jar:2021.1]
	at org.springframework.context.support.DefaultLifecycleProcessor.doStop(DefaultLifecycleProcessor.java:234) [spring-context-5.3.3.jar:5.3.3]
	at org.springframework.context.support.DefaultLifecycleProcessor.access$300(DefaultLifecycleProcessor.java:54) [spring-context-5.3.3.jar:5.3.3]
	at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.stop(DefaultLifecycleProcessor.java:373) [spring-context-5.3.3.jar:5.3.3]
	at org.springframework.context.support.DefaultLifecycleProcessor.stopBeans(DefaultLifecycleProcessor.java:206) [spring-context-5.3.3.jar:5.3.3]
	at org.springframework.context.support.DefaultLifecycleProcessor.onClose(DefaultLifecycleProcessor.java:129) [spring-context-5.3.3.jar:5.3.3]
	at org.springframework.context.support.AbstractApplicationContext.doClose(AbstractApplicationContext.java:1072) [spring-context-5.3.3.jar:5.3.3]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.doClose(ServletWebServerApplicationContext.java:171) [spring-boot-2.4.2.jar:2.4.2]
	at org.springframework.context.support.AbstractApplicationContext$1.run(AbstractApplicationContext.java:996) [spring-context-5.3.3.jar:5.3.3]

2. Solution

2.1web The server is switched to tomcat

Direct replacement , Problem solving

2.2 Make your own cancellation compensation

import cn.hutool.core.util.StrUtil;
import cn.hutool.http.HttpRequest;
import cn.hutool.http.HttpResponse;
import cn.hutool.http.HttpUtil;
import cn.hutool.http.Method;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.cloud.commons.util.InetUtils;
import org.springframework.stereotype.Component;

import java.util.HashMap;
import java.util.Map;

/** * nacos Registry compensation  * *  perform org.springframework.cloud.client.serviceregistry.AbstractAutoServiceRegistration#destroy() Before destruction , *  Probably org.springframework.boot.web.embedded.undertow.UndertowWebServer#stop() Has been executed . *  Lead to io.undertow.servlet.spec.ServletContextImpl#getInitParameterNames happen NPE, Therefore, it is impossible to get offline from the Registration Center . * * @Author: dong * @Date: 2021/12/24 15:24 */
@Slf4j
@Component
public class SelfNacosDiscovery {
    
    @Value("${spring.cloud.nacos.discovery.namespace:public}")
    private String namespaceId;
    private String clusterName = "DEFAULT";
    @Value("${spring.application.name:}")
    private String serviceName;
    @Value("${server.port:8080}")
    private String port;
    @Value("${spring.cloud.nacos.discovery.server-addr:}")
    private String nacosAddr;
    @Autowired
    private InetUtils inetUtils;

    /** *  Compensation cancellation  * com.alibaba.nacos.client.naming.net.NamingProxy#deregisterService(java.lang.String, com.alibaba.nacos.api.naming.pojo.Instance) *@Author dong *@Date 2021/12/24 15:58 *@param *@return */
    public void deregisterService(){
    
        HttpResponse execute = null;
        try{
    
            if(StrUtil.isAllNotBlank(namespaceId,serviceName,port,nacosAddr)){
    
                String name = "[email protected]@"+serviceName;
                String ipAddress = inetUtils.findFirstNonLoopbackHostInfo().getIpAddress();
                Map<String, Object> params = new HashMap<String, Object>(8);
                params.put("namespaceId", namespaceId);
                params.put("serviceName", name);
                params.put("clusterName", clusterName);
                // com.alibaba.cloud.nacos.NacosDiscoveryProperties.init
                params.put("ip", ipAddress);
                params.put("port", port);
                params.put("ephemeral", "true");
                log.info("nacos Compensation cancellation process ： Actuator information namespaceId={},serviceName={},clusterName={},ip={},port={}",namespaceId,
                        name,clusterName,ipAddress,port);
                HttpRequest request = HttpUtil.createRequest(Method.DELETE, nacosAddr + "/nacos/v1/ns/instance");
                execute = request.form(params).execute();
                log.info("nacos Compensation cancellation process results ：{}",execute.body());
            }else{
    
                log.warn("nacos The compensation cancellation process is not implemented ： Incomplete parameters ！");
            }
        }catch (Exception e){
    
            log.error("nacos Compensation cancellation process   abnormal ",e);
        }finally {
    
            if(execute!=null){
    
                execute.close();
            }
        }
    }

}

2.3 Use nacos Built in logout （ recommend ）

import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.client.serviceregistry.AbstractAutoServiceRegistration;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.event.EventListener;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;

@Slf4j
@Component
public class SelfNacosDiscovery {
    
    @Resource
    private AbstractAutoServiceRegistration abstractAutoServiceRegistration;

    @EventListener(ContextClosedEvent.class)
    public void doDeregister() {
    
        log.info("nacos Compensation cancellation process , Start ");
        try {
    
            abstractAutoServiceRegistration.destroy();
        }catch (Exception e){
    
        }
        log.info("nacos Compensation cancellation process , end ");
    }
}

20220609 to update
2.3 When the service is stopped, an exception will be printed . as follows ：

org.springframework.beans.factory.BeanCreationNotAllowedException: Error creating bean with name 'selfNacosDiscovery': Singleton bean creation not allowed while singletons of this factory are in destruction (Do not request a bean from a BeanFactory in a destroy method implementation!)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton
	....

SelfNacosDiscovery Just a little modification ：

import lombok.extern.slf4j.Slf4j;
import org.springframework.cloud.client.serviceregistry.AbstractAutoServiceRegistration;
import org.springframework.context.event.ContextClosedEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;

@Slf4j
@Component
public class SelfNacosDiscovery implements ApplicationListener<ContextClosedEvent>{
    
    @Resource
    private AbstractAutoServiceRegistration abstractAutoServiceRegistration;

    @EventListener(ContextClosedEvent.class)
    public void doDeregister() {
    
        log.info("nacos Compensation cancellation process , Start ");
        try {
    
            abstractAutoServiceRegistration.destroy();
        }catch (Exception e){
    
        }
        log.info("nacos Compensation cancellation process , end ");
    }
    
    @Override
    public void onApplicationEvent(ContextClosedEvent event) {
    
        doDeregister();
    }
}