added controller metrics function to component base

staging/src/k8s.io/component-base/metrics/prometheus/controllers/metrics.go

@@ -0,0 +1,56 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package controllers
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var (
+	// Metrics provides access to all controllerreadiness metrics.
+	Metrics = newControllerMetrics()
+)
+
+// ControllerMetrics includes all the metrics of the proxy server.
+type ControllerMetrics struct {
+	controllerInstanceCount *prometheus.GaugeVec
+}
+
+// newControllerMetrics create a new ControllerMetrics, configured with default metric names.
+func newControllerMetrics() *ControllerMetrics {
+	controllerInstanceCount := prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "managed_controller_instance_count",
+			Help: "Instances of individual controllers currently running",
+		},
+		[]string{"controller_name", "controller_manager"},
+	)
+	prometheus.MustRegister(controllerInstanceCount)
+	return &ControllerMetrics{
+		controllerInstanceCount: controllerInstanceCount,
+	}
+}
+
+// ControllerStarted sets the controllerInstanceCount to 1.
+func (a *ControllerMetrics) ControllerStarted(controllerName string, controllerManager string) {
+	a.controllerInstanceCount.With(prometheus.Labels{"controller_name": controllerName, "controller_manager": controllerManager}).Set(float64(1))
+}
+
+// ControllerStopped sets the controllerInstanceCount to 0.
+func (a *ControllerMetrics) ControllerStopped(controllerName string, controllerManager string) {
+	a.controllerInstanceCount.With(prometheus.Labels{"controller_name": controllerName, "controller_manager": controllerManager}).Set(float64(0))
+}