feat(metrics): export cached_images gauge

Author: plaffitt

cmd/cache/main.go

@@ -99,6 +99,8 @@ func main() {
 		os.Exit(1)
 	}
 
+	controllers.RegisterMetrics(mgr.GetClient())
+
 	setupLog.Info("starting manager")
 	if err := mgr.Start(ctrl.SetupSignalHandler()); err != nil {
 		setupLog.Error(err, "problem running manager")

controllers/collector.go

@@ -1,8 +1,14 @@
 package controllers
 
 import (
+	"context"
+	"strconv"
+
+	kuikenixiov1alpha1 "github.com/enix/kube-image-keeper/api/v1alpha1"
 	kuikMetrics "github.com/enix/kube-image-keeper/internal/metrics"
 	"github.com/prometheus/client_golang/prometheus"
+	"sigs.k8s.io/controller-runtime/pkg/client"
+	"sigs.k8s.io/controller-runtime/pkg/log"
 	"sigs.k8s.io/controller-runtime/pkg/metrics"
 )
 
@@ -25,13 +31,50 @@ var (
 			Help:      "Number of images removed from cache successfully",
 		},
 	)
+	cachedImagesMetric = prometheus.BuildFQName(kuikMetrics.Namespace, subsystem, "cached_images")
+	cachedImagesHelp   = "Number of images expected to be cached"
+	cachedImagesDesc   = prometheus.NewDesc(cachedImagesMetric, cachedImagesHelp, []string{"cached", "expiring"}, nil)
 )
 
-func init() {
+func RegisterMetrics(client client.Client) {
 	// Register custom metrics with the global prometheus registry
 	metrics.Registry.MustRegister(
 		imagePutInCache,
 		imageRemovedFromCache,
 		kuikMetrics.NewInfo(subsystem),
+		&ControllerCollector{
+			Client: client,
+		},
 	)
 }
+
+func cachedImagesWithLabelValues(gaugeVec *prometheus.GaugeVec, cachedImage *kuikenixiov1alpha1.CachedImage) prometheus.Gauge {
+	return gaugeVec.WithLabelValues(strconv.FormatBool(cachedImage.Status.IsCached), strconv.FormatBool(cachedImage.Spec.ExpiresAt != nil))
+}
+
+type ControllerCollector struct {
+	client.Client
+}
+
+func (c *ControllerCollector) Describe(ch chan<- *prometheus.Desc) {
+	ch <- cachedImagesDesc
+}
+
+func (c *ControllerCollector) Collect(ch chan<- prometheus.Metric) {
+	cachedImageList := &kuikenixiov1alpha1.CachedImageList{}
+	if err := c.List(context.Background(), cachedImageList); err == nil {
+		cachedImageGaugeVec := prometheus.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: cachedImagesMetric,
+				Help: cachedImagesHelp,
+			},
+			[]string{"cached", "expiring"},
+		)
+		for _, cachedImage := range cachedImageList.Items {
+			cachedImagesWithLabelValues(cachedImageGaugeVec, &cachedImage).Inc()
+		}
+		cachedImageGaugeVec.Collect(ch)
+	} else {
+		log.FromContext(context.TODO()).Error(err, "could not collect "+cachedImagesMetric+" metric")
+	}
+}