VPA: Add features gates; add InPlaceVerticalScaling feature gate

Signed-off-by: Max Cao <[email protected]>

Author: maxcao13

vertical-pod-autoscaler/pkg/features/features.go

@@ -0,0 +1,53 @@
+/*
+Copyright 2025 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package features
+
+import (
+	"k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/component-base/featuregate"
+)
+
+const (
+	// Every feature gate should add method here following this template:
+	//
+	// // alpha: v1.X
+	// MyFeature featuregate.Feature = "MyFeature".
+
+	// InPlaceVerticalScaling is a feature gate for enabling the InPlaceOrRecreate update mode to be used.
+	// Requires InPlacePodVerticalScaling feature-gate to be enabled on the Kubernetes cluster itself.
+	//
+	// TODO(maxcao13): fill this in
+	// alpha: v...
+	// beta: v...
+	// GA: v...
+	InPlaceVerticalScaling featuregate.Feature = "InPlaceVerticalScaling"
+)
+
+var MutableFeatureGate featuregate.MutableFeatureGate = featuregate.NewFeatureGate()
+
+// defaultVPAFeatureGates consists of all known vertical-pod-autoscaler-specific feature keys.
+var defaultVPAFeatureGates = map[featuregate.Feature]featuregate.FeatureSpec{
+	InPlaceVerticalScaling: {Default: false, PreRelease: featuregate.Alpha},
+}
+
+func Enabled(f featuregate.Feature) bool {
+	return MutableFeatureGate.Enabled(f)
+}
+
+func init() {
+	runtime.Must(MutableFeatureGate.Add(defaultVPAFeatureGates))
+}

vertical-pod-autoscaler/pkg/updater/eviction/pods_eviction_restriction.go

@@ -36,6 +36,7 @@ import (
 
 	resource_updates "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/admission-controller/resource"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/admission-controller/resource/pod/patch"
+	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/features"
 
 	vpa_types "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/apis/autoscaling.k8s.io/v1"
 )
@@ -433,6 +434,9 @@ func setUpInformer(kubeClient kube_client.Interface, kind controllerKind) (cache
 
 // CanInPlaceUpdate performs the same checks
 func (e *podsEvictionRestrictionImpl) CanInPlaceUpdate(pod *apiv1.Pod) bool {
+	if !features.Enabled(features.InPlaceVerticalScaling) {
+		return false
+	}
 	cr, present := e.podToReplicaCreatorMap[GetPodID(pod)]
 	if present {
 		// If our QoS class is guaranteed, we can't change the resources without a restart

vertical-pod-autoscaler/pkg/updater/logic/updater.go

@@ -43,6 +43,7 @@ import (
 	vpa_clientset "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/client/clientset/versioned"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/client/clientset/versioned/scheme"
 	vpa_lister "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/client/listers/autoscaling.k8s.io/v1"
+	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/features"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/target"
 	controllerfetcher "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/target/controller_fetcher"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/updater/eviction"
@@ -235,28 +236,34 @@ func (u *updater) RunOnce(ctx context.Context) {
 		vpaSize := len(livePods)
 		controlledPodsCounter.Add(vpaSize, vpaSize)
 		evictionLimiter := u.evictionFactory.NewPodsEvictionRestriction(livePods, vpa, u.patchCalculators)
-		podsForUpdate := u.getPodsUpdateOrder(filterNonEvictablePods(livePods, evictionLimiter), vpa)
+		podsForUpdate := u.getPodsUpdateOrder(filterNonUpdatablePods(livePods, evictionLimiter), vpa)
 		evictablePodsCounter.Add(vpaSize, len(podsForUpdate))
 
 		withInPlaceUpdatable := false
 		withInPlaceUpdated := false
 		withEvictable := false
 		withEvicted := false
 
+		logDisabledFeatureGate := false
+
 		for _, pod := range podsForUpdate {
 			if vpa_api_util.GetUpdateMode(vpa) == vpa_types.UpdateModeInPlaceOrRecreate {
-				withInPlaceUpdatable = true
-				fallBackToEviction, err := u.AttemptInPlaceUpdate(ctx, vpa, pod, evictionLimiter)
-				if err != nil {
-					klog.V(0).InfoS("In-place update failed", "error", err, "pod", klog.KObj(pod))
-					return
-				}
-				if fallBackToEviction {
-					klog.V(4).InfoS("Falling back to eviction for pod", "pod", klog.KObj(pod))
+				if features.Enabled(features.InPlaceVerticalScaling) {
+					withInPlaceUpdatable = true
+					fallBackToEviction, err := u.AttemptInPlaceUpdate(ctx, vpa, pod, evictionLimiter)
+					if err != nil {
+						klog.V(0).InfoS("In-place update failed", "error", err, "pod", klog.KObj(pod))
+						return
+					}
+					if fallBackToEviction {
+						klog.V(4).InfoS("Falling back to eviction for pod", "pod", klog.KObj(pod))
+					} else {
+						withInPlaceUpdated = true
+						metrics_updater.AddInPlaceUpdatedPod(vpaSize)
+						continue
+					}
 				} else {
-					withInPlaceUpdated = true
-					metrics_updater.AddInPlaceUpdatedPod(vpaSize)
-					continue
+					logDisabledFeatureGate = true
 				}
 			}
 
@@ -291,6 +298,9 @@ func (u *updater) RunOnce(ctx context.Context) {
 		if withEvicted {
 			vpasWithEvictedPodsCounter.Add(vpaSize, 1)
 		}
+		if logDisabledFeatureGate {
+			klog.InfoS("Warning: feature gate is not enabled for this updateMode", "featuregate", features.InPlaceVerticalScaling, "updateMode", vpa_types.UpdateModeInPlaceOrRecreate)
+		}
 	}
 	timer.ObserveStep("EvictPods")
 }
@@ -323,10 +333,10 @@ func (u *updater) getPodsUpdateOrder(pods []*apiv1.Pod, vpa *vpa_types.VerticalP
 	return priorityCalculator.GetSortedPods(u.evictionAdmission)
 }
 
-func filterNonEvictablePods(pods []*apiv1.Pod, evictionRestriction eviction.PodsEvictionRestriction) []*apiv1.Pod {
+func filterNonUpdatablePods(pods []*apiv1.Pod, evictionRestriction eviction.PodsEvictionRestriction) []*apiv1.Pod {
 	result := make([]*apiv1.Pod, 0)
 	for _, pod := range pods {
-		if evictionRestriction.CanEvict(pod) {
+		if evictionRestriction.CanEvict(pod) || evictionRestriction.CanInPlaceUpdate(pod) {
 			result = append(result, pod)
 		}
 	}
@@ -375,6 +385,9 @@ func newEventRecorder(kubeClient kube_client.Interface) record.EventRecorder {
 }
 
 func (u *updater) AttemptInPlaceUpdate(ctx context.Context, vpa *vpa_types.VerticalPodAutoscaler, pod *apiv1.Pod, evictionLimiter eviction.PodsEvictionRestriction) (fallBackToEviction bool, err error) {
+	if features.Enabled(features.InPlaceVerticalScaling) {
+		return false, fmt.Errorf("can't in-place update pod, %s not enabled", features.InPlaceVerticalScaling)
+	}
 	klog.V(4).InfoS("Checking preconditions for attemping in-place update", "pod", klog.KObj(pod))
 	if !evictionLimiter.CanInPlaceUpdate(pod) {
 		if pod.Status.QOSClass == apiv1.PodQOSGuaranteed {

vertical-pod-autoscaler/pkg/updater/main.go

@@ -38,6 +38,7 @@ import (
 	"k8s.io/autoscaler/vertical-pod-autoscaler/common"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/admission-controller/resource/pod/patch"
 	vpa_clientset "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/client/clientset/versioned"
+	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/features"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/target"
 	controllerfetcher "k8s.io/autoscaler/vertical-pod-autoscaler/pkg/target/controller_fetcher"
 	"k8s.io/autoscaler/vertical-pod-autoscaler/pkg/updater/inplace"
@@ -90,6 +91,8 @@ func main() {
 	leaderElection := defaultLeaderElectionConfiguration()
 	componentbaseoptions.BindLeaderElectionFlags(&leaderElection, pflag.CommandLine)
 
+	features.MutableFeatureGate.AddFlag(pflag.CommandLine)
+
 	kube_flag.InitFlags()
 	klog.V(1).InfoS("Vertical Pod Autoscaler Updater", "version", common.VerticalPodAutoscalerVersion())