*: add learner field in endpoint status

Added learner field to endpoint status API.

etcdserver/api/membership/cluster.go

@@ -693,3 +693,22 @@ func mustDetectDowngrade(lg *zap.Logger, cv *semver.Version) {
 		}
 	}
 }
+
+// IsLearner returns if the local member is raft learner
+func (c *RaftCluster) IsLearner() bool {
+	c.Lock()
+	defer c.Unlock()
+	localMember, ok := c.members[c.localID]
+	if !ok {
+		if c.lg != nil {
+			c.lg.Panic(
+				"failed to find local ID in cluster members",
+				zap.String("cluster-id", c.cid.String()),
+				zap.String("local-member-id", c.localID.String()),
+			)
+		} else {
+			plog.Panicf("failed to find local ID %s in cluster %s", c.localID.String(), c.cid.String())
+		}
+	}
+	return localMember.IsLearner
+}

etcdserver/api/v3rpc/maintenance.go

@@ -55,6 +55,10 @@ type AuthGetter interface {
 	AuthStore() auth.AuthStore
 }
 
+type ClusterStatusGetter interface {
+	IsLearner() bool
+}
+
 type maintenanceServer struct {
 	lg  *zap.Logger
 	rg  etcdserver.RaftStatusGetter
@@ -63,10 +67,11 @@ type maintenanceServer struct {
 	a   Alarmer
 	lt  LeaderTransferrer
 	hdr header
+	cs  ClusterStatusGetter
 }
 
 func NewMaintenanceServer(s *etcdserver.EtcdServer) pb.MaintenanceServer {
-	srv := &maintenanceServer{lg: s.Cfg.Logger, rg: s, kg: s, bg: s, a: s, lt: s, hdr: newHeader(s)}
+	srv := &maintenanceServer{lg: s.Cfg.Logger, rg: s, kg: s, bg: s, a: s, lt: s, hdr: newHeader(s), cs: s}
 	return &authMaintenanceServer{srv, s}
 }
 
@@ -179,6 +184,7 @@ func (ms *maintenanceServer) Status(ctx context.Context, ar *pb.StatusRequest) (
 		RaftTerm:         ms.rg.Term(),
 		DbSize:           ms.bg.Backend().Size(),
 		DbSizeInUse:      ms.bg.Backend().SizeInUse(),
+		IsLearner:        ms.cs.IsLearner(),
 	}
 	if resp.Leader == raft.None {
 		resp.Errors = append(resp.Errors, etcdserver.ErrNoLeader.Error())

etcdserver/server.go

@@ -2440,3 +2440,8 @@ func (s *EtcdServer) Alarms() []*pb.AlarmMember {
 func (s *EtcdServer) Logger() *zap.Logger {
 	return s.lg
 }
+
+// IsLearner returns if the local member is raft learner
+func (s *EtcdServer) IsLearner() bool {
+	return s.cluster.IsLearner()
+}