Introduce API changes and fetaure gate CPU startup boost

Author: kamarabbas99

vertical-pod-autoscaler/deploy/vpa-v1-crd-gen.yaml

@@ -372,9 +372,94 @@ spec:
                           - Auto
                           - "Off"
                           type: string
+                        startupBoost:
+                          description: |-
+                            StartupBoost specifies the startup boost policy for the container.
+                            This overrides any pod-level startup boost policy.
+                          properties:
+                            cpu:
+                              description: |-
+                                CPU specifies the CPU startup boost policy.
+                                If this field is not set, no startup boost is applied.
+                              properties:
+                                duration:
+                                  description: |-
+                                    Duration indicates for how long to keep the pod boosted after it goes to Ready.
+                                    Defaults to 0s.
+                                  type: string
+                                factor:
+                                  description: |-
+                                    Factor specifies the factor to apply to the CPU request.
+                                    This field is to be used only when Type is "Factor".
+                                  format: int32
+                                  type: integer
+                                quantity:
+                                  anyOf:
+                                  - type: integer
+                                  - type: string
+                                  description: |-
+                                    Quantity specifies the absolute CPU resource quantity.
+                                    This field is to be used only when Type is "Quantity".
+                                  pattern: ^(\+|-)?(([0-9]+(\.[0-9]*)?)|(\.[0-9]+))(([KMGTPE]i)|[numkMGTPE]|([eE](\+|-)?(([0-9]+(\.[0-9]*)?)|(\.[0-9]+))))?$
+                                  x-kubernetes-int-or-string: true
+                                type:
+                                  description: |-
+                                    Type specifies the kind of boost to apply.
+                                    Supported values are: "Factor", "Quantity".
+                                    Defaults to "Factor".
+                                  enum:
+                                  - Factor
+                                  - Quantity
+                                  type: string
+                              required:
+                              - type
+                              type: object
+                          type: object
                       type: object
                     type: array
                 type: object
+              startupBoost:
+                description: StartupBoost specifies the startup boost policy for the
+                  pod.
+                properties:
+                  cpu:
+                    description: |-
+                      CPU specifies the CPU startup boost policy.
+                      If this field is not set, no startup boost is applied.
+                    properties:
+                      duration:
+                        description: |-
+                          Duration indicates for how long to keep the pod boosted after it goes to Ready.
+                          Defaults to 0s.
+                        type: string
+                      factor:
+                        description: |-
+                          Factor specifies the factor to apply to the CPU request.
+                          This field is to be used only when Type is "Factor".
+                        format: int32
+                        type: integer
+                      quantity:
+                        anyOf:
+                        - type: integer
+                        - type: string
+                        description: |-
+                          Quantity specifies the absolute CPU resource quantity.
+                          This field is to be used only when Type is "Quantity".
+                        pattern: ^(\+|-)?(([0-9]+(\.[0-9]*)?)|(\.[0-9]+))(([KMGTPE]i)|[numkMGTPE]|([eE](\+|-)?(([0-9]+(\.[0-9]*)?)|(\.[0-9]+))))?$
+                        x-kubernetes-int-or-string: true
+                      type:
+                        description: |-
+                          Type specifies the kind of boost to apply.
+                          Supported values are: "Factor", "Quantity".
+                          Defaults to "Factor".
+                        enum:
+                        - Factor
+                        - Quantity
+                        type: string
+                    required:
+                    - type
+                    type: object
+                type: object
               targetRef:
                 description: |-
                   TargetRef points to the controller managing the set of pods for the

vertical-pod-autoscaler/docs/features.md

@@ -7,6 +7,7 @@
 - [CPU Recommendation Rounding](#cpu-recommendation-rounding)
 - [Memory Recommendation Rounding](#memory-recommendation-rounding)
 - [In-Place Updates](#in-place-updates-inplaceorrecreate)
+- [CPU Startup Boost](#cpu-startup-boost)
 
 ## Limits control
 
@@ -80,7 +81,7 @@ To enable this feature, set the `--round-memory-bytes` flag when running the VPA
 
 ## In-Place Updates (`InPlaceOrRecreate`)
 
-> [!WARNING] 
+> [!WARNING]
 > FEATURE STATE: VPA v1.4.0 [alpha]
 
 VPA supports in-place updates to reduce disruption when applying resource recommendations. This feature leverages Kubernetes' in-place update capabilities (which is in beta as of Kubernetes 1.33) to modify container resources without requiring pod recreation.
@@ -124,7 +125,7 @@ Enable the feature by setting the following flags in VPA components ( for both u
 
 ```bash
 --feature-gates=InPlaceOrRecreate=true
-``` 
+```
 
 ### Limitations
 
@@ -151,4 +152,61 @@ VPA provides metrics to track in-place update operations:
 * `vpa_in_place_updated_pods_total`: Number of pods successfully updated in-place
 * `vpa_vpas_with_in_place_updatable_pods_total`: Number of VPAs with pods eligible for in-place updates
 * `vpa_vpas_with_in_place_updated_pods_total`: Number of VPAs with successfully in-place updated pods
-* `vpa_updater_failed_in_place_update_attempts_total`: Number of failed attempts to update pods in-place.
+* `vpa_updater_failed_in_place_update_attempts_total`: Number of failed attempts to update pods in-place.
+
+## CPU Startup Boost
+
+> [!WARNING]
+> FEATURE STATE: VPA v1.5.0 [alpha]
+
+The CPU Startup Boost feature allows VPA to temporarily increase CPU requests and limits for containers during pod startup. This can help workloads that have high CPU demands during their initialization phase, such as Java applications, to start faster. Once the pod is considered `Ready` and an optional duration has passed, VPA scales the CPU resources back down to their normal levels using an in-place resize.
+
+For more details, see [AEP-7862: CPU Startup Boost](https://github.com/kubernetes/autoscaler/tree/master/vertical-pod-autoscaler/enhancements/7862-cpu-startup-boost).
+
+### Usage
+
+CPU Startup Boost is configured via the `startupBoost` field in the `VerticalPodAutoscalerSpec` or within the per-container `containerPolicies`. This allows for both global and per-container boost configurations.
+
+This example enables a startup boost for all containers in the targeted deployment. The CPU will be multiplied by a factor of 3 for 10 seconds after the pod becomes ready.
+
+```yaml
+apiVersion: "autoscaling.k8s.io/v1"
+kind: VerticalPodAutoscaler
+metadata:
+  name: example-vpa
+spec:
+  targetRef:
+    apiVersion: "apps/v1"
+    kind: Deployment
+    name: example
+  updatePolicy:
+    updateMode: "Recreate"
+  startupBoost:
+    cpu:
+      value: "3"
+      duration: 10s
+```
+
+### Behavior
+
+1.  When a pod managed by the VPA is created, the VPA Admission Controller applies the CPU boost.
+2.  The VPA Updater monitors the pod. Once the pod's condition is `Ready` and the `startupBoost.cpu.duration` has elapsed, it scales the CPU resources down in-place.
+3.  The scale-down/unboost target is either the VPA recommendation (if VPA is enabled for the container) or the original CPU resources defined in the pod spec.
+
+### Requirements
+
+*   Kubernetes 1.33+ with the `InPlacePodVerticalScaling` feature gate enabled.
+*   VPA version 1.5.0+ with the `CPUStartupBoost` feature gate enabled.
+
+### Configuration
+
+Enable the feature by setting the `CPUStartupBoost` feature gate in the VPA admission-controller and updater components:
+
+```bash
+--feature-gates=CPUStartupBoost=true
+```
+
+The `startupBoost` field has the following sub-fields:
+*   `cpu.type`: The type of boost. Can be `Factor` (default) to multiply the CPU, or `Quantity` to set a specific CPU value.
+*   `cpu.value`: The magnitude of the boost. A multiplier (e.g., "2") for `Factor` type, or a resource quantity (e.g., "500m") for `Quantity` type.
+*   `cpu.duration`: (Optional) How long to keep the boost active *after* the pod becomes `Ready`. Defaults to `0s`.

vertical-pod-autoscaler/docs/flags.md

@@ -14,7 +14,7 @@ This document is auto-generated from the flag definitions in the VPA admission-c
 | `address` | string |  ":8944" | The address to expose Prometheus metrics.  |
 | `alsologtostderr` |  |  | log to standard error as well as files (no effect when -logtostderr=true) |
 | `client-ca-file` | string |  "/etc/tls-certs/caCert.pem" | Path to CA PEM file.  |
-| `feature-gates` | mapStringBool |  | A set of key=value pairs that describe feature gates for alpha/experimental features. Options are:<br>AllAlpha=true\|false (ALPHA - default=false)<br>AllBeta=true\|false (BETA - default=false)<br>InPlaceOrRecreate=true\|false (ALPHA - default=false) |
+| `feature-gates` | mapStringBool |  | A set of key=value pairs that describe feature gates for alpha/experimental features. Options are:<br>AllAlpha=true\|false (ALPHA - default=false)<br>AllBeta=true\|false (BETA - default=false)<br>CPUStartupBoost=true\|false (ALPHA - default=false)<br>InPlaceOrRecreate=true\|false (ALPHA - default=false) |
 | `ignored-vpa-object-namespaces` | string |  | A comma-separated list of namespaces to ignore when searching for VPA objects. Leave empty to avoid ignoring any namespaces. These namespaces will not be cleaned by the garbage collector. |
 | `kube-api-burst` | float |  100 | QPS burst limit when making requests to Kubernetes apiserver  |
 | `kube-api-qps` | float |  50 | QPS limit when making requests to Kubernetes apiserver  |
@@ -144,7 +144,7 @@ This document is auto-generated from the flag definitions in the VPA updater cod
 | `eviction-rate-burst` | int |  1 | Burst of pods that can be evicted.  |
 | `eviction-rate-limit` | float |  | Number of pods that can be evicted per seconds. A rate limit set to 0 or -1 will disable<br>the rate limiter. (default -1) |
 | `eviction-tolerance` | float |  0.5 | Fraction of replica count that can be evicted for update, if more than one pod can be evicted.  |
-| `feature-gates` | mapStringBool |  | A set of key=value pairs that describe feature gates for alpha/experimental features. Options are:<br>AllAlpha=true\|false (ALPHA - default=false)<br>AllBeta=true\|false (BETA - default=false)<br>InPlaceOrRecreate=true\|false (ALPHA - default=false) |
+| `feature-gates` | mapStringBool |  | A set of key=value pairs that describe feature gates for alpha/experimental features. Options are:<br>AllAlpha=true\|false (ALPHA - default=false)<br>AllBeta=true\|false (BETA - default=false)<br>CPUStartupBoost=true\|false (ALPHA - default=false)<br>InPlaceOrRecreate=true\|false (ALPHA - default=false) |
 | `ignored-vpa-object-namespaces` | string |  | A comma-separated list of namespaces to ignore when searching for VPA objects. Leave empty to avoid ignoring any namespaces. These namespaces will not be cleaned by the garbage collector. |
 | `in-recommendation-bounds-eviction-lifetime-threshold` |  |  12h0m0s | duration   Pods that live for at least that long can be evicted even if their request is within the [MinRecommended...MaxRecommended] range  |
 | `kube-api-burst` | float |  100 | QPS burst limit when making requests to Kubernetes apiserver  |

vertical-pod-autoscaler/pkg/admission-controller/resource/vpa/handler.go

@@ -163,9 +163,16 @@ func ValidateVPA(vpa *vpa_types.VerticalPodAutoscaler, isCreate bool) error {
 					return fmt.Errorf("controlledValues shouldn't be specified if container scaling mode is off")
 				}
 			}
+			if err := validateStartupBoost(policy.StartupBoost, isCreate); err != nil {
+				return fmt.Errorf("invalid startupBoost in container %s: %v", policy.ContainerName, err)
+			}
 		}
 	}
 
+	if err := validateStartupBoost(vpa.Spec.StartupBoost, isCreate); err != nil {
+		return fmt.Errorf("invalid startupBoost: %v", err)
+	}
+
 	if isCreate && vpa.Spec.TargetRef == nil {
 		return fmt.Errorf("targetRef is required. If you're using v1beta1 version of the API, please migrate to v1")
 	}
@@ -177,6 +184,48 @@ func ValidateVPA(vpa *vpa_types.VerticalPodAutoscaler, isCreate bool) error {
 	return nil
 }
 
+func validateStartupBoost(startupBoost *vpa_types.StartupBoost, isCreate bool) error {
+	if startupBoost == nil {
+		return nil
+	}
+
+	if !features.Enabled(features.CPUStartupBoost) && isCreate {
+		return fmt.Errorf("in order to use startupBoost, you must enable feature gate %s in the admission-controller args", features.CPUStartupBoost)
+	}
+
+	cpuBoost := startupBoost.CPU
+	if cpuBoost == nil {
+		return nil
+	}
+	boostType := cpuBoost.Type
+	if boostType == nil {
+		// Default to Factor when type is not specified.
+		defaultType := vpa_types.FactorStartupBoostType
+		boostType = &defaultType
+	}
+
+	if *boostType != vpa_types.FactorStartupBoostType && *boostType != vpa_types.QuantityStartupBoostType {
+		return fmt.Errorf("unexpected StartupBoost.CPU.Type value %s", *boostType)
+	}
+
+	if *boostType == vpa_types.FactorStartupBoostType {
+		if cpuBoost.Factor == nil {
+			return fmt.Errorf("StartupBoost.CPU.Factor is required when Type is Factor")
+		}
+		if *cpuBoost.Factor < 1 {
+			return fmt.Errorf("invalid StartupBoost.CPU.Factor: must be >= 1 for Type Factor")
+		}
+	} else if *boostType == vpa_types.QuantityStartupBoostType {
+		if cpuBoost.Quantity == nil {
+			return fmt.Errorf("StartupBoost.CPU.Quantity is required when Type is Quantity")
+		}
+		if err := validateCPUResolution(*cpuBoost.Quantity); err != nil {
+			return fmt.Errorf("invalid StartupBoost.CPU.Quantity: %v", err)
+		}
+	}
+	return nil
+}
+
 func validateResourceResolution(name corev1.ResourceName, val apires.Quantity) error {
 	switch name {
 	case corev1.ResourceCPU: