Refactor metric prometheus leader helper

internal/ingress/metric/main.go

@@ -18,9 +18,12 @@ package metric
 
 import (
 	"os"
+	"sync/atomic"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
+	"k8s.io/klog"
+
 	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/ingress-nginx/internal/ingress"
 	"k8s.io/ingress-nginx/internal/ingress/annotations/class"
@@ -153,6 +156,11 @@ func (c *collector) Stop() {
 }
 
 func (c *collector) SetSSLExpireTime(servers []*ingress.Server) {
+	if !isLeader() {
+		return
+	}
+
+	klog.V(2).Infof("Updating ssl expiration metrics.")
 	c.ingressController.SetSSLExpireTime(servers)
 }
 
@@ -162,11 +170,30 @@ func (c *collector) SetHosts(hosts sets.String) {
 
 // OnStartedLeading indicates the pod was elected as the leader
 func (c *collector) OnStartedLeading(electionID string) {
+	setLeader(true)
 	c.ingressController.OnStartedLeading(electionID)
 }
 
 // OnStoppedLeading indicates the pod stopped being the leader
 func (c *collector) OnStoppedLeading(electionID string) {
+	setLeader(false)
 	c.ingressController.OnStoppedLeading(electionID)
 	c.ingressController.RemoveAllSSLExpireMetrics(c.registry)
 }
+
+var (
+	currentLeader uint32
+)
+
+func setLeader(leader bool) {
+	var i uint32
+	if leader {
+		i = 1
+	}
+
+	atomic.StoreUint32(&currentLeader, i)
+}
+
+func isLeader() bool {
+	return atomic.LoadUint32(&currentLeader) != 0
+}