metrics master is leader

weed/server/master_grpc_server.go

@@ -237,7 +237,10 @@ func (ms *MasterServer) KeepConnected(stream master_pb.Seaweed_KeepConnectedServ
 			}
 		case <-ticker.C:
 			if !ms.Topo.IsLeader() {
+				stats.MasterRaftIsleader.Set(0)
 				return ms.informNewLeader(stream)
+			} else {
+				stats.MasterRaftIsleader.Set(1)
 			}
 		case <-stopChan:
 			return nil

weed/stats/metrics.go

@@ -28,6 +28,14 @@ var (
 			Help:      "Counter of master client leader updates.",
 		}, []string{"type"})
 
+	MasterRaftIsleader = prometheus.NewGauge(
+		prometheus.GaugeOpts{
+			Namespace: "SeaweedFS",
+			Subsystem: "master",
+			Name:      "is leader",
+			Help:      "is leader",
+		})
+
 	MasterReceivedHeartbeatCounter = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Namespace: "SeaweedFS",
@@ -153,6 +161,11 @@ var (
 )
 
 func init() {
+	Gather.MustRegister(MasterClientConnectCounter)
+	Gather.MustRegister(MasterRaftIsleader)
+	Gather.MustRegister(MasterReceivedHeartbeatCounter)
+	Gather.MustRegister(MasterLeaderChangeCounter)
+
 	Gather.MustRegister(FilerRequestCounter)
 	Gather.MustRegister(FilerRequestHistogram)
 	Gather.MustRegister(FilerStoreCounter)