Describe the bug
spring boot discovery client throw exceptions, but config client not get error , in the nacos console board to check the service registry info , refresh the service in the service list , the service is unstable in the list. although I have checked cluster status is in healty status , but the service discovery client still throw the exception below .

`021-04-11 11:48:59.686 ERROR 4188 --- [ing.beat.sender] com.alibaba.nacos.client.naming : [NA] failed to request

com.alibaba.nacos.api.exception.NacosException: server is DOWN now, please try again later!
at com.alibaba.nacos.client.naming.net.NamingProxy.callServer(NamingProxy.java:615)
at com.alibaba.nacos.client.naming.net.NamingProxy.reqApi(NamingProxy.java:526)
at com.alibaba.nacos.client.naming.net.NamingProxy.reqApi(NamingProxy.java:498)
at com.alibaba.nacos.client.naming.net.NamingProxy.sendBeat(NamingProxy.java:433)
at com.alibaba.nacos.client.naming.beat.BeatReactor$BeatTask.run(BeatReactor.java:167)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run$$$capture(FutureTask.java:266)
at java.util.concurrent.FutureTask.run(FutureTask.java)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)`

{ "lastRefreshTime": 1618113171231, "raftMetaData": { "metaDataMap": { "naming_instance_metadata": { "leader": "nacos-0.nacos-hs.prod.svc.cluster.local:7848", "raftGroupMember": [ "nacos-1.nacos-hs.prod.svc.cluster.local:7848", "nacos-0.nacos-hs.prod.svc.cluster.local:7848" ], "term": 1 }, "naming_persistent_service": { "leader": "nacos-0.nacos-hs.prod.svc.cluster.local:7848", "raftGroupMember": [ "nacos-1.nacos-hs.prod.svc.cluster.local:7848", "nacos-0.nacos-hs.prod.svc.cluster.local:7848" ], "term": 1 }, "naming_persistent_service_v2": { "leader": "nacos-0.nacos-hs.prod.svc.cluster.local:7848", "raftGroupMember": [ "nacos-1.nacos-hs.prod.svc.cluster.local:7848", "nacos-0.nacos-hs.prod.svc.cluster.local:7848" ], "term": 1 }, "naming_service_metadata": { "leader": "nacos-0.nacos-hs.prod.svc.cluster.local:7848", "raftGroupMember": [ "nacos-1.nacos-hs.prod.svc.cluster.local:7848", "nacos-0.nacos-hs.prod.svc.cluster.local:7848" ], "term": 1 } } }, "raftPort": "7848", "readyToUpgrade": true, "version": "2.0.0" }

Expected behavior
service registry should work properly as the service instance work well .

Acutally behavior
set up the nacos cluster , and login to the nacos console ,and check cluster status

How to Reproduce
Steps to reproduce the behavior:

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2. Click on '....'
3. Scroll down to '....'
4. See error

Desktop (please complete the following information):

• OS: [e.g. Centos]
• Version [e.g. nacos-server 1.3.1, nacos-client 1.3.1]
• Module [e.g. naming/config]
• SDK [e.g. original, spring-cloud-alibaba-nacos, dubbo]

Additional context
Add any other context about the problem here.