fix: Allow ScaledObject.MinReplicaCount to be set to 0

CHANGELOG.md

@@ -282,6 +282,7 @@ Here is an overview of all new **experimental** features:
 
 ### Fixes
 
+- **General**: Allow ScaledObject.MinReplicaCount to be set to 0 ([#5570](https://github.com/kedacore/keda/issues/5570))
 - **General**: Fix CVE-2024-28180 in github.com/go-jose/go-jose/v3 ([#5617](https://github.com/kedacore/keda/pull/5617))
 - **General**: Fix fallback logic in formula-based evaluation ([#5666](https://github.com/kedacore/keda/issues/5666))
 - **General**: Fix wrong scaler active value and paused value that are pushed to OpenTelemetry ([#5705](https://github.com/kedacore/keda/issues/5705))

apis/keda/v1alpha1/scaledobject_types.go

@@ -78,8 +78,8 @@ const (
 	// CompositeMetricName is used for scalingModifiers composite metric
 	CompositeMetricName string = "composite-metric"
 
-	defaultHPAMinReplicas int32 = 1
-	defaultHPAMaxReplicas int32 = 100
+	defaultMinReplicas int32 = 0
+	defaultMaxReplicas int32 = 100
 )
 
 // ScaledObjectSpec is the spec for a ScaledObject resource
@@ -237,31 +237,27 @@ func (so *ScaledObject) IsUsingModifiers() bool {
 	return so.Spec.Advanced != nil && !reflect.DeepEqual(so.Spec.Advanced.ScalingModifiers, ScalingModifiers{})
 }
 
-// getHPAMinReplicas returns MinReplicas based on definition in ScaledObject or default value if not defined
-func (so *ScaledObject) GetHPAMinReplicas() *int32 {
-	if so.Spec.MinReplicaCount != nil && *so.Spec.MinReplicaCount > 0 {
-		return so.Spec.MinReplicaCount
+// MinReplicaCount returns MinReplicaCount based on definition in ScaledObject or default value if not defined
+func (so *ScaledObject) MinReplicaCount() int32 {
+	if so.Spec.MinReplicaCount != nil {
+		return *so.Spec.MinReplicaCount
 	}
-	tmp := defaultHPAMinReplicas
-	return &tmp
+	return defaultMinReplicas
 }
 
-// getHPAMaxReplicas returns MaxReplicas based on definition in ScaledObject or default value if not defined
-func (so *ScaledObject) GetHPAMaxReplicas() int32 {
+// MaxReplicaCount returns MaxReplicaCount based on definition in ScaledObject or default value if not defined
+func (so *ScaledObject) MaxReplicaCount() int32 {
 	if so.Spec.MaxReplicaCount != nil {
 		return *so.Spec.MaxReplicaCount
 	}
-	return defaultHPAMaxReplicas
+	return defaultMaxReplicas
 }
 
 // checkReplicaCountBoundsAreValid checks that Idle/Min/Max ReplicaCount defined in ScaledObject are correctly specified
 // i.e. that Min is not greater than Max or Idle greater or equal to Min
 func CheckReplicaCountBoundsAreValid(scaledObject *ScaledObject) error {
-	min := int32(0)
-	if scaledObject.Spec.MinReplicaCount != nil {
-		min = *scaledObject.GetHPAMinReplicas()
-	}
-	max := scaledObject.GetHPAMaxReplicas()
+	min := scaledObject.MinReplicaCount()
+	max := scaledObject.MaxReplicaCount()
 
 	if min > max {
 		return fmt.Errorf("MinReplicaCount=%d must be less than MaxReplicaCount=%d", min, max)

controllers/keda/hpa.go

@@ -99,25 +99,24 @@ func (r *ScaledObjectReconciler) newHPAForScaledObject(ctx context.Context, logg
 		labels[key] = value
 	}
 
-	minReplicas := scaledObject.GetHPAMinReplicas()
-	maxReplicas := scaledObject.GetHPAMaxReplicas()
+	// minReplicas on HPA must be > 0 without HPAScaleToZero feature.
+	minReplicas := max(scaledObject.MinReplicaCount(), 1)
+	maxReplicas := scaledObject.MaxReplicaCount()
 
 	pausedCount, err := executor.GetPausedReplicaCount(scaledObject)
 	if err != nil {
 		return nil, err
 	}
 	if pausedCount != nil {
-		// MinReplicas on HPA can't be 0
-		if *pausedCount == 0 {
-			*pausedCount = 1
-		}
-		minReplicas = pausedCount
-		maxReplicas = *pausedCount
+		// minReplicas on HPA must be > 0 without HPAScaleToZero feature.
+		replicas := max(*pausedCount, 1)
+		minReplicas = replicas
+		maxReplicas = replicas
 	}
 
 	hpa := &autoscalingv2.HorizontalPodAutoscaler{
 		Spec: autoscalingv2.HorizontalPodAutoscalerSpec{
-			MinReplicas: minReplicas,
+			MinReplicas: &minReplicas,
 			MaxReplicas: maxReplicas,
 			Metrics:     scaledObjectMetricSpecs,
 			Behavior:    behavior,