Fix bug: Agent never update its Instance HeartbeatTime

[evanxuhe]

Please answer these questions before submitting pull request

• Why submit this pull request?

• Bug fix

• Related issues

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Bug fix

• Bug description.
  Agent never update its Instance HeartbeatTime

Beacause the judgment statement in org.apache.skywalking.apm.agent.core.remote.AppAndServiceRegisterClientthat compares current timestamp with lastSegmentUpdateTime will be always negative and never works

if (lastSegmentTime - System.currentTimeMillis() > 60 * 1000) {
                                instanceDiscoveryServiceBlockingStub.heartbeat(ApplicationInstanceHeartbeat.newBuilder()
                                    .setApplicationInstanceId(RemoteDownstreamConfig.Agent.APPLICATION_INSTANCE_ID)
                                    .setHeartbeatTime(System.currentTimeMillis())
                                    .build());
                            }

• How to fix?
  Fix the judgement sequence putting System.currentTimeMillis() before

                            if ( System.currentTimeMillis() - lastSegmentTime > 60 * 1000) {
                                instanceDiscoveryServiceBlockingStub.heartbeat(ApplicationInstanceHeartbeat.newBuilder()
                                    .setApplicationInstanceId(RemoteDownstreamConfig.Agent.APPLICATION_INSTANCE_ID)
                                    .setHeartbeatTime(System.currentTimeMillis())
                                    .build());
                            }

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New feature or improvement

• Describe the details and related test reports.

[wu-sheng]

Is this only a 5.x bug? Or still exist in master 5.x protocol?

[evanxuhe]

relavant disccussion before
#3150

[evanxuhe]

Is this only a 5.x bug? Or still exist in master 5.x protocol?

I think it exists in 5.x master agent
I dont understand what you wanna know? . 5.x protocol Does it be relevant with this?

[wu-sheng]

No related. Misread from me. Sorry.