add kruise_manager_is_leader metric

Signed-off-by: hatowang <[email protected]>

add leader metric for kruise_manager.

main.go

@@ -46,6 +46,7 @@ import (
 	appsv1beta1 "github.com/openkruise/kruise/apis/apps/v1beta1"
 	policyv1alpha1 "github.com/openkruise/kruise/apis/policy/v1alpha1"
 	"github.com/openkruise/kruise/pkg/controller"
+	_ "github.com/openkruise/kruise/pkg/util/metrics/leadership"
 	// +kubebuilder:scaffold:imports
 )
 

pkg/util/metrics/leadership/leader.go

@@ -0,0 +1,44 @@
+package leadership
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"k8s.io/client-go/tools/leaderelection"
+	"sigs.k8s.io/controller-runtime/pkg/metrics"
+)
+
+var leaderMetric = promauto.NewGauge(
+	prometheus.GaugeOpts{
+		Name: "kruise_manager_is_leader",
+		Help: "Gauge the leader of kruise-manager",
+	},
+)
+
+func init() {
+	metrics.Registry.MustRegister(leaderMetric)
+	leaderelection.SetProvider(newMetricProvider())
+}
+
+func newMetricProvider() leaderelection.MetricsProvider {
+	return metricsProvider{}
+}
+
+type metricsProvider struct{}
+type switchMetric struct{}
+
+var (
+	_ leaderelection.MetricsProvider = metricsProvider{}
+	_ leaderelection.SwitchMetric    = switchMetric{}
+)
+
+func (_ metricsProvider) NewLeaderMetric() leaderelection.SwitchMetric {
+	return switchMetric{}
+}
+
+func (_ switchMetric) On(_ string) {
+	leaderMetric.Set(1)
+}
+
+func (s switchMetric) Off(string) {
+	leaderMetric.Set(0)
+}