add gc metrics and collect sync errors

pkg/controller/garbagecollector/garbagecollector.go

@@ -46,6 +46,7 @@ import (
 	"k8s.io/klog/v2"
 	c "k8s.io/kubernetes/pkg/controller"
 	"k8s.io/kubernetes/pkg/controller/apis/config/scheme"
+	"k8s.io/kubernetes/pkg/controller/garbagecollector/metrics"
 
 	// import known versions
 	_ "k8s.io/client-go/kubernetes"
@@ -123,6 +124,8 @@ func NewGarbageCollector(
 		ignoredResources: ignoredResources,
 	}
 
+	metrics.Register()
+
 	return gc, nil
 }
 
@@ -179,6 +182,7 @@ func (gc *GarbageCollector) Sync(discoveryClient discovery.ServerResourcesInterf
 		// This can occur if there is an internal error in GetDeletableResources.
 		if len(newResources) == 0 {
 			klog.V(2).Infof("no resources reported by discovery, skipping garbage collector sync")
+			metrics.GarbageCollectorResourcesSyncError.Inc()
 			return
 		}
 
@@ -203,6 +207,7 @@ func (gc *GarbageCollector) Sync(discoveryClient discovery.ServerResourcesInterf
 				newResources = GetDeletableResources(discoveryClient)
 				if len(newResources) == 0 {
 					klog.V(2).Infof("no resources reported by discovery (attempt %d)", attempt)
+					metrics.GarbageCollectorResourcesSyncError.Inc()
 					return false, nil
 				}
 			}
@@ -226,6 +231,7 @@ func (gc *GarbageCollector) Sync(discoveryClient discovery.ServerResourcesInterf
 			// attempt.
 			if err := gc.resyncMonitors(newResources); err != nil {
 				utilruntime.HandleError(fmt.Errorf("failed to sync resource monitors (attempt %d): %v", attempt, err))
+				metrics.GarbageCollectorResourcesSyncError.Inc()
 				return false, nil
 			}
 			klog.V(4).Infof("resynced monitors")
@@ -237,6 +243,7 @@ func (gc *GarbageCollector) Sync(discoveryClient discovery.ServerResourcesInterf
 			// note that workers stay paused until we successfully resync.
 			if !cache.WaitForNamedCacheSync("garbage collector", waitForStopOrTimeout(stopCh, period), gc.dependencyGraphBuilder.IsSynced) {
 				utilruntime.HandleError(fmt.Errorf("timed out waiting for dependency graph builder sync during GC sync (attempt %d)", attempt))
+				metrics.GarbageCollectorResourcesSyncError.Inc()
 				return false, nil
 			}
 

pkg/controller/garbagecollector/metrics/metrics.go

@@ -0,0 +1,45 @@
+/*
+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 metrics
+
+import (
+	"sync"
+
+	"k8s.io/component-base/metrics"
+	"k8s.io/component-base/metrics/legacyregistry"
+)
+
+const GarbageCollectorControllerSubsystem = "garbagecollector_controller"
+
+var (
+	GarbageCollectorResourcesSyncError = metrics.NewCounter(
+		&metrics.CounterOpts{
+			Subsystem:      GarbageCollectorControllerSubsystem,
+			Name:           "resources_sync_error_total",
+			Help:           "Number of garbage collector resources sync errors",
+			StabilityLevel: metrics.ALPHA,
+		})
+)
+
+var registerMetrics sync.Once
+
+// Register registers GarbageCollectorController metrics.
+func Register() {
+	registerMetrics.Do(func() {
+		legacyregistry.MustRegister(GarbageCollectorResourcesSyncError)
+	})
+}