Add promehteus metric about leader election status

internal/ingress/controller/nginx.go

@@ -269,8 +269,12 @@ func (n *NGINXController) Start() {
 			if n.syncStatus != nil {
 				go n.syncStatus.Run(stopCh)
 			}
+
+			n.metricCollector.OnStartedLeading(n.cfg.ElectionID)
 		},
 		OnStoppedLeading: func() {
+			n.metricCollector.OnStoppedLeading(n.cfg.ElectionID)
+
 			// Remove prometheus metrics related to SSL certificates
 			srvs := sets.NewString()
 			for _, s := range n.runningConfig.Servers {

internal/ingress/metric/collectors/controller.go

@@ -46,6 +46,8 @@ type Controller struct {
 
 	constLabels prometheus.Labels
 	labels      prometheus.Labels
+
+	leaderElection *prometheus.GaugeVec
 }
 
 // NewController creates a new prometheus collector for the
@@ -112,6 +114,13 @@ func NewController(pod, namespace, class string) *Controller {
 			},
 			sslLabelHost,
 		),
+		leaderElection: prometheus.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "leader_election_status",
+				Help: "Gauge reporting status of the leader election, 0 indicates follower, 1 indicates leader. 'name' is the string used to identify the lease",
+			},
+			[]string{"name"},
+		),
 	}
 
 	return cm
@@ -127,6 +136,16 @@ func (cm *Controller) IncReloadErrorCount() {
 	cm.reloadOperationErrors.With(cm.constLabels).Inc()
 }
 
+// OnStartedLeading indicates the pod is not the current leader
+func (cm *Controller) OnStartedLeading(electionID string) {
+	cm.leaderElection.WithLabelValues(electionID).Set(0)
+}
+
+// OnStoppedLeading indicates the pod is not the current leader
+func (cm *Controller) OnStoppedLeading(electionID string) {
+	cm.leaderElection.WithLabelValues(electionID).Set(1.0)
+}
+
 // ConfigSuccess set a boolean flag according to the output of the controller configuration reload
 func (cm *Controller) ConfigSuccess(hash uint64, success bool) {
 	if success {

internal/ingress/metric/dummy.go

@@ -52,3 +52,9 @@ func (dc DummyCollector) SetSSLExpireTime([]*ingress.Server) {}
 
 // SetHosts ...
 func (dc DummyCollector) SetHosts(hosts sets.String) {}
+
+// OnStartedLeading indicates the pod is not the current leader
+func (dc DummyCollector) OnStartedLeading(electionID string) {}
+
+// OnStoppedLeading indicates the pod is not the current leader
+func (dc DummyCollector) OnStoppedLeading(electionID string) {}

internal/ingress/metric/main.go

@@ -36,6 +36,9 @@ type Collector interface {
 	IncReloadCount()
 	IncReloadErrorCount()
 
+	OnStartedLeading(string)
+	OnStoppedLeading(string)
+
 	RemoveMetrics(ingresses, endpoints []string)
 
 	SetSSLExpireTime([]*ingress.Server)
@@ -147,3 +150,13 @@ func (c *collector) SetSSLExpireTime(servers []*ingress.Server) {
 func (c *collector) SetHosts(hosts sets.String) {
 	c.socket.SetHosts(hosts)
 }
+
+// OnStartedLeading indicates the pod is not the current leader
+func (c *collector) OnStartedLeading(electionID string) {
+	c.ingressController.OnStartedLeading(electionID)
+}
+
+// OnStoppedLeading indicates the pod is not the current leader
+func (c *collector) OnStoppedLeading(electionID string) {
+	c.ingressController.OnStoppedLeading(electionID)
+}