Only the leader updates metrics for SSL certificate expiration

internal/ingress/controller/controller.go

@@ -190,7 +190,11 @@ func (n *NGINXController) syncIngress(interface{}) error {
 		klog.Infof("Backend successfully reloaded.")
 		n.metricCollector.ConfigSuccess(hash, true)
 		n.metricCollector.IncReloadCount()
-		n.metricCollector.SetSSLExpireTime(servers)
+
+		if n.isLeader() {
+			klog.V(2).Infof("Updating ssl expiration metrics.")
+			n.metricCollector.SetSSLExpireTime(servers)
+		}
 	}
 
 	isFirstSync := n.runningConfig.Equal(&ingress.Configuration{})

internal/ingress/controller/nginx.go

@@ -31,6 +31,7 @@ import (
 	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"syscall"
 	"text/template"
 	"time"
@@ -255,6 +256,8 @@ type NGINXController struct {
 	fileSystem filesystem.Filesystem
 
 	metricCollector metric.Collector
+
+	currentLeader uint32
 }
 
 // Start starts a new NGINX master process running in the foreground.
@@ -278,19 +281,15 @@ func (n *NGINXController) Start() {
 				go n.syncStatus.Run(stopCh)
 			}
 
+			n.setLeader(true)
 			n.metricCollector.OnStartedLeading(electionID)
+			// manually update SSL expiration metrics
+			// (to not wait for a reload)
+			n.metricCollector.SetSSLExpireTime(n.runningConfig.Servers)
 		},
 		OnStoppedLeading: func() {
+			n.setLeader(false)
 			n.metricCollector.OnStoppedLeading(electionID)
-
-			// Remove prometheus metrics related to SSL certificates
-			srvs := sets.NewString()
-			for _, s := range n.runningConfig.Servers {
-				if !srvs.Has(s.Hostname) {
-					srvs.Insert(s.Hostname)
-				}
-			}
-			n.metricCollector.RemoveMetrics(nil, srvs.List())
 		},
 		PodName:      n.podInfo.Name,
 		PodNamespace: n.podInfo.Namespace,
@@ -1129,3 +1128,15 @@ func buildRedirects(servers []*ingress.Server) []*redirect {
 
 	return redirectServers
 }
+
+func (n *NGINXController) setLeader(leader bool) {
+	var i uint32
+	if leader {
+		i = 1
+	}
+	atomic.StoreUint32(&n.currentLeader, i)
+}
+
+func (n *NGINXController) isLeader() bool {
+	return atomic.LoadUint32(&n.currentLeader) != 0
+}