Nacos Client brushing log

[caojianqiang1984]

Which Component
org.springframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:0.9.0.RELEASE

Describe the bug
只要请求不存在的服务，就会不断刷日志

To Reproduce
Steps to reproduce the behavior:

1. 注入服务发现客户端
   @Autowired
   private DiscoveryClient discoveryClient;
2. 偿试获取一个不存在的服务
   discoveryClient.getInstances("service-i");

当服务"service-i"不存在或者下线时，客户端就会不断打印如下日志
11:03:47.307 ERROR [] HostReactor.updateServiceNow:278 [NA] failed to update serviceName: DEFAULT_GROUP@@DBB-Applyjava.lang.IllegalStateException: failed to req API:/nacos/v1/ns/instance/list after all servers([service.dev.furong.ink:8848]) tried: failed to req API:http://service.dev.furong.ink:8848/nacos/v1/ns/instance/list. code:404 msg: service not found: DEFAULT_GROUP@@service-i
at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:380)
at com.alibaba.nacos.client.naming.net.NamingProxy.reqAPI(NamingProxy.java:304)
at com.alibaba.nacos.client.naming.net.NamingProxy.queryList(NamingProxy.java:217)
at com.alibaba.nacos.client.naming.core.HostReactor.updateServiceNow(HostReactor.java:273)
at com.alibaba.nacos.client.naming.core.HostReactor$UpdateTask.run(HostReactor.java:318)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)

Additional context
Add any other context about the problem here.
版本号：
Java11 + spring cloud Greenwich.RELEASE + org.springframework.cloud:spring-cloud-starter-alibaba-nacos-discovery:0.9.0.RELEASE

[fangjian0423]

Hi. @caojianqiang1984

This is a normal phenomenon. It will print code:404 msg: service not found:... when service not found in nacos.

I think we could create a issue in nacos to discuss whether throw 404 exception when service not found.

Nacos issue: https://github.com/alibaba/nacos/issues

[caojianqiang1984]

@fangjian0423 打印日志很正常，但它是刷日志，每一秒刷一次，刷个不停，直到找到这个服务为止。而这个服务是不存在的，日志会每隔一秒打印一次不停的刷

[fangjian0423]

refer alibaba/nacos#1252 and #661.