feat: expose keda_scaler_active Prometheus metric (#4124)

Signed-off-by: Zbynek Roubalik <zroubalik@gmail.com>

Signed-off-by: Zbynek Roubalik <zroubalik@gmail.com>

CHANGELOG.md

@@ -51,6 +51,7 @@ Here is an overview of all **stable** additions:
 
 - **General**: Introduce admission webhooks to automatically validate resource changes to prevent misconfiguration and enforce best practices ([#3755](https://github.com/kedacore/keda/issues/3755))
 - **General**: Introduce new ArangoDB Scaler ([#4000](https://github.com/kedacore/keda/issues/4000))
+- **Prometheus Metrics**: Introduce scaler activity in Prometheus metrics ([#4114](https://github.com/kedacore/keda/issues/4114))
 - **Prometheus Metrics**: Introduce scaler latency in Prometheus metrics ([#4037](https://github.com/kedacore/keda/issues/4037))
 
 Here is an overview of all new **experimental** features:

pkg/prommetrics/prommetrics.go

@@ -64,6 +64,15 @@ var (
 		},
 		metricLabels,
 	)
+	scalerActive = prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Namespace: DefaultPromMetricsNamespace,
+			Subsystem: "scaler",
+			Name:      "active",
+			Help:      "Activity of a Scaler Metric",
+		},
+		metricLabels,
+	)
 	scalerErrors = prometheus.NewCounterVec(
 		prometheus.CounterOpts{
 			Namespace: DefaultPromMetricsNamespace,
@@ -106,6 +115,7 @@ func init() {
 	metrics.Registry.MustRegister(scalerErrorsTotal)
 	metrics.Registry.MustRegister(scalerMetricsValue)
 	metrics.Registry.MustRegister(scalerMetricsLatency)
+	metrics.Registry.MustRegister(scalerActive)
 	metrics.Registry.MustRegister(scalerErrors)
 	metrics.Registry.MustRegister(scaledObjectErrors)
 
@@ -123,6 +133,16 @@ func RecordScalerLatency(namespace string, scaledObject string, scaler string, s
 	scalerMetricsLatency.With(getLabels(namespace, scaledObject, scaler, scalerIndex, metric)).Set(value)
 }
 
+// RecordScalerActive create a measurement of the activity of the scaler
+func RecordScalerActive(namespace string, scaledObject string, scaler string, scalerIndex int, metric string, active bool) {
+	activeVal := 0
+	if active {
+		activeVal = 1
+	}
+
+	scalerActive.With(getLabels(namespace, scaledObject, scaler, scalerIndex, metric)).Set(float64(activeVal))
+}
+
 // RecordScalerError counts the number of errors occurred in trying get an external metric used by the HPA
 func RecordScalerError(namespace string, scaledObject string, scaler string, scalerIndex int, metric string, err error) {
 	if err != nil {

pkg/scaling/scale_handler.go

@@ -579,6 +579,7 @@ func (h *scaleHandler) getScaledObjectState(ctx context.Context, scaledObject *k
 				}
 			}
 			prommetrics.RecordScalerError(scaledObject.Namespace, scaledObject.Name, scalerName, scalerIndex, metricName, err)
+			prommetrics.RecordScalerActive(scaledObject.Namespace, scaledObject.Name, scalerName, scalerIndex, metricName, isMetricActive)
 		}
 	}
 

tests/internals/prometheus_metrics/prometheus_metrics_test.go

@@ -229,6 +229,7 @@ func TestPrometheusMetrics(t *testing.T) {
 
 	testScalerMetricValue(t)
 	testScalerMetricLatency(t)
+	testScalerActiveMetric(t)
 	testMetricsServerScalerMetricValue(t)
 	testOperatorMetrics(t, kc, data)
 	testWebhookMetrics(t, data)
@@ -314,6 +315,29 @@ func testScalerMetricLatency(t *testing.T) {
 	}
 }
 
+func testScalerActiveMetric(t *testing.T) {
+	t.Log("--- testing scaler active metric ---")
+
+	family := fetchAndParsePrometheusMetrics(t, fmt.Sprintf("curl --insecure %s", kedaOperatorPrometheusURL))
+
+	if val, ok := family["keda_scaler_active"]; ok {
+		var found bool
+		metrics := val.GetMetric()
+		for _, metric := range metrics {
+			labels := metric.GetLabel()
+			for _, label := range labels {
+				if *label.Name == labelScaledObject && *label.Value == scaledObjectName {
+					assert.Equal(t, float64(1), *metric.Gauge.Value)
+					found = true
+				}
+			}
+		}
+		assert.Equal(t, true, found)
+	} else {
+		t.Errorf("metric not available")
+	}
+}
+
 // [DEPRECATED] handle exporting Prometheus metrics from Operator to Metrics Server
 func testMetricsServerScalerMetricValue(t *testing.T) {
 	t.Log("--- testing scaler metric value in metrics server ---")