fileobserver: prometheus counter for observed actions

pkg/controller/fileobserver/observer.go

@@ -28,6 +28,19 @@ const (
 	FileDeleted
 )
 
+func (t ActionType) name() string {
+	switch t {
+	case FileCreated:
+		return "create"
+	case FileDeleted:
+		return "delete"
+	case FileModified:
+		return "modified"
+	default:
+		return "unknown"
+	}
+}
+
 // String returns human readable form of action taken on a file.
 func (t ActionType) String(filename string) string {
 	switch t {

pkg/controller/fileobserver/observer_polling.go

@@ -11,6 +11,8 @@ import (
 	"time"
 
 	"k8s.io/apimachinery/pkg/util/wait"
+	"k8s.io/component-base/metrics"
+	"k8s.io/component-base/metrics/legacyregistry"
 	"k8s.io/klog"
 )
 
@@ -114,6 +116,9 @@ func (o *pollingObserver) processReactors(stopCh <-chan struct{}) {
 					klog.Infof("Observed file %q has been modified (old=%q, new=%q)", filename, lastKnownFileState.hash, currentFileState.hash)
 					action = FileModified
 				}
+				// increment metrics counter for this file
+				observerActionsMetrics.WithLabelValues(filename, action.name()).Inc()
+				// execute the register reactor
 				if err := reactors[i](filename, action); err != nil {
 					klog.Errorf("Reactor for %q failed: %v", filename, err)
 				}
@@ -132,6 +137,19 @@ func (o *pollingObserver) processReactors(stopCh <-chan struct{}) {
 	}
 }
 
+var observerActionsMetrics = metrics.NewCounterVec(&metrics.CounterOpts{
+	Subsystem:      "fileobserver",
+	Name:           "action_count",
+	Help:           "Counter for every observed action for all monitored files",
+	StabilityLevel: metrics.ALPHA,
+}, []string{"name", "filename"})
+
+func init() {
+	(&sync.Once{}).Do(func() {
+		legacyregistry.MustRegister(observerActionsMetrics)
+	})
+}
+
 // Run will start a new observer.
 func (o *pollingObserver) Run(stopChan <-chan struct{}) {
 	klog.Info("Starting file observer")