Nacos 作为配置中心，微服务总是过段时间自行宕机下线

nacos 环境

nacos 运行的版本：2.0.3 。

nacos 为单机运行非集群，启动命令 ./startup.sh -m standalone (使用的是 dev 账户启动的，非 root)

nacos 的配置文件 nacos/conf/application.properties 中没有配置 mysql 链接信息。

微服务

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.2</version>
    </parent>
    
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>2020.0.1</version>
        <type>pom</type>
        <scope>import</scope>
    </dependency>
    
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-alibaba-dependencies</artifactId>
        <version>2021.1</version>
        <type>pom</type>
        <scope>import</scope>
    </dependency>

版本参考的是： https://github.com/alibaba/spring-cloud-alibaba/wiki/%E7%89%88%E6%9C%AC%E8%AF%B4%E6%98%8E

问题现象

nacos 是正常启动的，微服务启动注册到 127.0.0.1:8848(使用的是 dev 账户启动的，非 root)

只用到了注册服务，服务发现，没有用到别的 nacos 功能

spring:
  cloud:
    nacos:
      discovery:
        server-addr: 127.0.0.1:8848

微服务都能够正常注册到 nacos，但是，过段时间（晚上 18 点重启微服务），次日早上微服务便会自动停机，nacos 后台管理系统中就看到微服务下线了（很多个微服务都下线），这些微服务的日志为：

2021-10-22 11:00:41.433  WARN 19068 --- [      Thread-10] c.a.nacos.common.notify.NotifyCenter     : [NotifyCenter] Start destroying Publisher
2021-10-22 11:00:41.433  WARN 19068 --- [      Thread-10] c.a.nacos.common.notify.NotifyCenter     : [NotifyCenter] Destruction of the end
2021-10-22 11:00:41.436  WARN 19068 --- [       Thread-4] c.a.n.common.http.HttpClientBeanHolder   : [HttpClientBeanHolder] Start destroying common HttpClient
2021-10-22 11:00:41.437  WARN 19068 --- [       Thread-4] c.a.n.common.http.HttpClientBeanHolder   : [HttpClientBeanHolder] Destruction of the end
2021-10-22 11:00:41.444  INFO 19068 --- [extShutdownHook] o.s.s.c.ThreadPoolTaskScheduler          : Shutting down ExecutorService 'Nacos-Watch-Task-Scheduler'
2021-10-22 11:00:41.445  INFO 19068 --- [extShutdownHook] c.a.c.n.registry.NacosServiceRegistry    : De-registering from Nacos Server now...
2021-10-22 11:00:41.448  INFO 19068 --- [extShutdownHook] c.a.c.n.registry.NacosServiceRegistry    : De-registration finished.
2021-10-22 11:00:49.101  WARN 19068 --- [extShutdownHook] o.s.b.f.support.DisposableBeanAdapter    : Destroy method 'close' on bean with name 'nacosServiceRegistry' threw an exception: java.lang.NullPointerException