[servicecomb-service-center] branch master updated: Add some comments

[li...@apache.org]

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littlecui pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/servicecomb-service-center.git


The following commit(s) were added to refs/heads/master by this push:
     new 2a60d63  Add some comments
2a60d63 is described below

commit 2a60d6370a3ad85bb52fa1d63c541888b16629f6
Author: little-cui <su...@qq.com>
AuthorDate: Mon Mar 25 15:59:17 2019 +0800

    Add some comments
---
 server/service/instance.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/server/service/instance.go b/server/service/instance.go
index cd95050..e67d64e 100644
--- a/server/service/instance.go
+++ b/server/service/instance.go
@@ -103,6 +103,11 @@ func (s *InstanceService) Register(ctx context.Context, in *pb.RegisterInstanceR
 	//允许自定义id
 	if len(instance.InstanceId) > 0 {
 		// keep alive the lease ttl
+		// there are two reasons for sending a heartbeat here:
+		// 1. in the scenario the instance has been removed, 
+		//    the cast of registration operation can be reduced.
+		// 2. in the self-protection scenario, the instance is unhealthy 
+		//    and needs to be re-registered.
 		resp, err := s.Heartbeat(ctx, &pb.HeartbeatRequest{ServiceId: instance.ServiceId, InstanceId: instance.InstanceId})
 		switch resp.Response.Code {
 		case pb.Response_SUCCESS: