fix(HPA): ignore the container resource metrics in HPA controller when the feature gate is disabled

cmd/kube-controller-manager/app/autoscaling.go

@@ -21,13 +21,16 @@ package app
 
 import (
 	"context"
+
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/util/feature"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/scale"
 	"k8s.io/controller-manager/controller"
 	"k8s.io/klog/v2"
 	"k8s.io/kubernetes/pkg/controller/podautoscaler"
 	"k8s.io/kubernetes/pkg/controller/podautoscaler/metrics"
+	"k8s.io/kubernetes/pkg/features"
 
 	resourceclient "k8s.io/metrics/pkg/client/clientset/versioned/typed/metrics/v1beta1"
 	"k8s.io/metrics/pkg/client/custom_metrics"
@@ -92,6 +95,7 @@ func startHPAControllerWithMetricsClient(ctx context.Context, controllerContext
 		controllerContext.ComponentConfig.HPAController.HorizontalPodAutoscalerTolerance,
 		controllerContext.ComponentConfig.HPAController.HorizontalPodAutoscalerCPUInitializationPeriod.Duration,
 		controllerContext.ComponentConfig.HPAController.HorizontalPodAutoscalerInitialReadinessDelay.Duration,
+		feature.DefaultFeatureGate.Enabled(features.HPAContainerMetrics),
 	).Run(ctx, int(controllerContext.ComponentConfig.HPAController.ConcurrentHorizontalPodAutoscalerSyncs))
 	return nil, true, nil
 }

pkg/controller/podautoscaler/horizontal.go

@@ -108,6 +108,9 @@ type HorizontalController struct {
 	// Storage of HPAs and their selectors.
 	hpaSelectors    *selectors.BiMultimap
 	hpaSelectorsMux sync.Mutex
+
+	// feature gates
+	containerResourceMetricsEnabled bool
 }
 
 // NewHorizontalController creates a new HorizontalController.
@@ -124,7 +127,7 @@ func NewHorizontalController(
 	tolerance float64,
 	cpuInitializationPeriod,
 	delayOfInitialReadinessStatus time.Duration,
-
+	containerResourceMetricsEnabled bool,
 ) *HorizontalController {
 	broadcaster := record.NewBroadcaster()
 	broadcaster.StartStructuredLogging(0)
@@ -145,6 +148,7 @@ func NewHorizontalController(
 		scaleDownEvents:                 map[string][]timestampedScaleEvent{},
 		scaleDownEventsLock:             sync.RWMutex{},
 		hpaSelectors:                    selectors.NewBiMultimap(),
+		containerResourceMetricsEnabled: containerResourceMetricsEnabled,
 	}
 
 	hpaInformer.Informer().AddEventHandlerWithResyncPeriod(
@@ -425,6 +429,13 @@ func (a *HorizontalController) computeReplicasForMetric(ctx context.Context, hpa
 			return 0, "", time.Time{}, condition, fmt.Errorf("failed to get %s resource metric value: %v", spec.Resource.Name, err)
 		}
 	case autoscalingv2.ContainerResourceMetricSourceType:
+		if !a.containerResourceMetricsEnabled {
+			// If the container resource metrics feature is disabled but the object has the one,
+			// that means the user enabled the feature once, created some HPAs with the container resource metrics, and disabled it finally.
+			// We cannot return errors in this case because that'll result in all HPAs with the container resource metric sources failing to scale down.
+			// Thus, here we silently ignore it and return current replica values so that it won't affect the autoscaling decision
+			return specReplicas, "", time.Time{}, condition, nil
+		}
 		replicaCountProposal, timestampProposal, metricNameProposal, condition, err = a.computeStatusForContainerResourceMetric(ctx, specReplicas, spec, hpa, selector, status)
 		if err != nil {
 			return 0, "", time.Time{}, condition, fmt.Errorf("failed to get %s container metric value: %v", spec.ContainerResource.Container, err)

pkg/controller/podautoscaler/horizontal_test.go

@@ -148,6 +148,8 @@ type testCase struct {
 
 	recommendations []timestampedRecommendation
 	hpaSelectors    *selectors.BiMultimap
+
+	containerResourceMetricsEnabled bool
 }
 
 // Needs to be called under a lock.
@@ -738,6 +740,7 @@ func (tc *testCase) setupController(t *testing.T) (*HorizontalController, inform
 		defaultTestingTolerance,
 		defaultTestingCPUInitializationPeriod,
 		defaultTestingDelayOfInitialReadinessStatus,
+		tc.containerResourceMetricsEnabled,
 	)
 	hpaController.hpaListerSynced = alwaysReady
 	if tc.recommendations != nil {
@@ -829,6 +832,38 @@ func TestScaleUpContainer(t *testing.T) {
 		reportedLevels:                  []uint64{300, 500, 700},
 		reportedCPURequests:             []resource.Quantity{resource.MustParse("1.0"), resource.MustParse("1.0"), resource.MustParse("1.0")},
 		useMetricsAPI:                   true,
+		containerResourceMetricsEnabled: true,
+	}
+	tc.runTest(t)
+}
+
+func TestIgnoreContainerMetric(t *testing.T) {
+	// when the container metric feature isn't enabled, it's ignored and HPA keeps the current replica.
+	tc := testCase{
+		minReplicas:             2,
+		maxReplicas:             6,
+		specReplicas:            3,
+		statusReplicas:          3,
+		expectedDesiredReplicas: 3,
+		metricsTarget: []autoscalingv2.MetricSpec{{
+			Type: autoscalingv2.ContainerResourceMetricSourceType,
+			ContainerResource: &autoscalingv2.ContainerResourceMetricSource{
+				Name: v1.ResourceCPU,
+				Target: autoscalingv2.MetricTarget{
+					Type:               autoscalingv2.UtilizationMetricType,
+					AverageUtilization: pointer.Int32(30),
+				},
+				Container: "container1",
+			},
+		}},
+		reportedLevels:      []uint64{300, 500, 700},
+		reportedCPURequests: []resource.Quantity{resource.MustParse("1.0"), resource.MustParse("1.0"), resource.MustParse("1.0")},
+		useMetricsAPI:       true,
+		expectedConditions: statusOkWithOverrides(autoscalingv2.HorizontalPodAutoscalerCondition{
+			Type:   autoscalingv2.AbleToScale,
+			Status: v1.ConditionTrue,
+			Reason: "ReadyForNewScale",
+		}),
 	}
 	tc.runTest(t)
 }
@@ -1361,6 +1396,7 @@ func TestScaleDownContainerResource(t *testing.T) {
 		}},
 		useMetricsAPI:                   true,
 		recommendations:                 []timestampedRecommendation{},
+		containerResourceMetricsEnabled: true,
 	}
 	tc.runTest(t)
 }
@@ -4536,6 +4572,7 @@ func TestMultipleHPAs(t *testing.T) {
 		defaultTestingTolerance,
 		defaultTestingCPUInitializationPeriod,
 		defaultTestingDelayOfInitialReadinessStatus,
+		false,
 	)
 	hpaController.scaleUpEvents = scaleUpEventsMap
 	hpaController.scaleDownEvents = scaleDownEventsMap