feat: add orphaned resource count metric (#20521)

Signed-off-by: jaehanbyun <awbrg789@naver.com>

Author: jaehanbyun

controller/appcontroller.go

@@ -628,6 +628,7 @@ func (ctrl *ApplicationController) getResourceTree(a *appv1.Application, managed
 			Message: fmt.Sprintf("Application has %d orphaned resources", len(orphanedNodes)),
 		}}
 	}
+	ctrl.metricsServer.SetOrphanedResourcesMetric(a, len(orphanedNodes))
 	a.Status.SetConditions(conditions, map[appv1.ApplicationConditionType]bool{appv1.ApplicationConditionOrphanedResourceWarning: true})
 	sort.Slice(orphanedNodes, func(i, j int) bool {
 		return orphanedNodes[i].ResourceRef.String() < orphanedNodes[j].ResourceRef.String()

controller/metrics/metrics.go

@@ -33,6 +33,7 @@ type MetricsServer struct {
 	syncCounter             *prometheus.CounterVec
 	kubectlExecCounter      *prometheus.CounterVec
 	kubectlExecPendingGauge *prometheus.GaugeVec
+	orphanedResourcesGauge  *prometheus.GaugeVec
 	k8sRequestCounter       *prometheus.CounterVec
 	clusterEventsCounter    *prometheus.CounterVec
 	redisRequestCounter     *prometheus.CounterVec
@@ -144,6 +145,14 @@ var (
 		},
 		[]string{"hostname", "initiator"},
 	)
+
+	orphanedResourcesGauge = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "argocd_app_orphaned_resources_count",
+			Help: "Number of orphaned resources per application",
+		},
+		descAppDefaultLabels,
+	)
 )
 
 // NewMetricsServer returns a new prometheus server which collects application metrics
@@ -188,6 +197,7 @@ func NewMetricsServer(addr string, appLister applister.ApplicationLister, appFil
 	registry.MustRegister(k8sRequestCounter)
 	registry.MustRegister(kubectlExecCounter)
 	registry.MustRegister(kubectlExecPendingGauge)
+	registry.MustRegister(orphanedResourcesGauge)
 	registry.MustRegister(reconcileHistogram)
 	registry.MustRegister(clusterEventsCounter)
 	registry.MustRegister(redisRequestCounter)
@@ -203,6 +213,7 @@ func NewMetricsServer(addr string, appLister applister.ApplicationLister, appFil
 		k8sRequestCounter:       k8sRequestCounter,
 		kubectlExecCounter:      kubectlExecCounter,
 		kubectlExecPendingGauge: kubectlExecPendingGauge,
+		orphanedResourcesGauge:  orphanedResourcesGauge,
 		reconcileHistogram:      reconcileHistogram,
 		clusterEventsCounter:    clusterEventsCounter,
 		redisRequestCounter:     redisRequestCounter,
@@ -241,6 +252,10 @@ func (m *MetricsServer) DecKubectlExecPending(command string) {
 	m.kubectlExecPendingGauge.WithLabelValues(m.hostname, command).Dec()
 }
 
+func (m *MetricsServer) SetOrphanedResourcesMetric(app *argoappv1.Application, numOrphanedResources int) {
+	m.orphanedResourcesGauge.WithLabelValues(app.Namespace, app.Name, app.Spec.GetProject()).Set(float64(numOrphanedResources))
+}
+
 // IncClusterEventsCount increments the number of cluster events
 func (m *MetricsServer) IncClusterEventsCount(server, group, kind string) {
 	m.clusterEventsCounter.WithLabelValues(server, group, kind).Inc()
@@ -290,6 +305,7 @@ func (m *MetricsServer) SetExpiration(cacheExpiration time.Duration) error {
 		m.syncCounter.Reset()
 		m.kubectlExecCounter.Reset()
 		m.kubectlExecPendingGauge.Reset()
+		m.orphanedResourcesGauge.Reset()
 		m.k8sRequestCounter.Reset()
 		m.clusterEventsCounter.Reset()
 		m.redisRequestCounter.Reset()

controller/metrics/metrics_test.go

@@ -509,6 +509,31 @@ argocd_app_reconcile_count{dest_server="https://localhost:6443",namespace="argoc
 	assertMetricsPrinted(t, appReconcileMetrics, body)
 }
 
+func TestOrphanedResourcesMetric(t *testing.T) {
+	cancel, appLister := newFakeLister()
+	defer cancel()
+	metricsServ, err := NewMetricsServer("localhost:8082", appLister, appFilter, noOpHealthCheck, []string{}, []string{})
+	require.NoError(t, err)
+
+	expectedMetrics := `
+# HELP argocd_app_orphaned_resources_count Number of orphaned resources per application
+# TYPE argocd_app_orphaned_resources_count gauge
+argocd_app_orphaned_resources_count{name="my-app-4",namespace="argocd",project="important-project"} 1
+`
+	app := newFakeApp(fakeApp4)
+	numOrphanedResources := 1
+	metricsServ.SetOrphanedResourcesMetric(app, numOrphanedResources)
+
+	req, err := http.NewRequest(http.MethodGet, "/metrics", nil)
+	require.NoError(t, err)
+	rr := httptest.NewRecorder()
+	metricsServ.Handler.ServeHTTP(rr, req)
+	assert.Equal(t, http.StatusOK, rr.Code)
+	body := rr.Body.String()
+	log.Println(body)
+	assertMetricsPrinted(t, expectedMetrics, body)
+}
+
 func TestMetricsReset(t *testing.T) {
 	cancel, appLister := newFakeLister()
 	defer cancel()