feat(admission): add autoscaling configuration

.changes/unreleased/added-20261020-223519.yaml

@@ -0,0 +1,3 @@
+kind: Added
+body: |-
+  Add horizontal autoscaling configuration for admission service

config/crd/kai.scheduler_configs.yaml

@@ -48,6 +48,36 @@ spec:
               admission:
                 description: Admission holds KAI admission webhooks
                 properties:
+                  autoscaling:
+                    description: Autoscaling configures horizontal autoscaling for
+                      the admission service
+                    properties:
+                      enabled:
+                        description: Enabled enables horizontal autoscaling for the
+                          admission service.
+                        type: boolean
+                      maxReplicas:
+                        description: MaxReplicas specifies the maximum number of admission
+                          replicas.
+                        format: int32
+                        minimum: 1
+                        type: integer
+                      targetCPUUtilizationPercentage:
+                        description: |-
+                          TargetCPUUtilizationPercentage specifies the target average CPU utilization
+                          across admission pods.
+                        format: int32
+                        maximum: 100
+                        minimum: 1
+                        type: integer
+                      targetInFlightRequests:
+                        description: |-
+                          TargetInFlightRequests specifies the target average number of in-flight
+                          webhook requests per admission pod.
+                        format: int32
+                        minimum: 1
+                        type: integer
+                    type: object
                   blockNvidiaVisibleDevices:
                     description: |-
                       BlockNvidiaVisibleDevices prevents pods from overriding the NVIDIA_VISIBLE_DEVICES

kai/v1/admission/admission.go

@@ -36,6 +36,10 @@ type Admission struct {
 	// +kubebuilder:validation:Optional
 	Replicas *int32 `json:"replicas,omitempty"`
 
+	// Autoscaling configures horizontal autoscaling for the admission service
+	// +kubebuilder:validation:Optional
+	Autoscaling *Autoscaling `json:"autoscaling,omitempty"`
+
 	// GPUSharing enables GPU sharing functionality for the admission service
 	// +kubebuilder:validation:Optional
 	GPUSharing *bool `json:"gpuSharing,omitempty"`
@@ -80,6 +84,35 @@ type Admission struct {
 	InPlacePodResize *InPlacePodResize `json:"inPlacePodResize,omitempty"`
 }
 
+// Autoscaling defines horizontal autoscaling configuration for the admission service.
+type Autoscaling struct {
+	// Enabled enables horizontal autoscaling for the admission service.
+	// +kubebuilder:validation:Optional
+	Enabled *bool `json:"enabled,omitempty"`
+
+	// MaxReplicas specifies the maximum number of admission replicas.
+	// +kubebuilder:validation:Optional
+	// +kubebuilder:validation:Minimum=1
+	MaxReplicas *int32 `json:"maxReplicas,omitempty"`
+
+	// TargetInFlightRequests specifies the target average number of in-flight
+	// webhook requests per admission pod.
+	// +kubebuilder:validation:Optional
+	// +kubebuilder:validation:Minimum=1
+	TargetInFlightRequests *int32 `json:"targetInFlightRequests,omitempty"`
+
+	// TargetCPUUtilizationPercentage specifies the target average CPU utilization
+	// across admission pods.
+	// +kubebuilder:validation:Optional
+	// +kubebuilder:validation:Minimum=1
+	// +kubebuilder:validation:Maximum=100
+	TargetCPUUtilizationPercentage *int32 `json:"targetCPUUtilizationPercentage,omitempty"`
+}
+
+func (a *Autoscaling) SetDefaultsWhereNeeded() {
+	a.Enabled = common.SetDefault(a.Enabled, ptr.To(false))
+}
+
 // InPlacePodResize configures KEP-1287 in-place pod resize admission behaviour.
 type InPlacePodResize struct {
 	// ValidateQuota enables best-effort hierarchical queue quota checks on
@@ -110,6 +143,10 @@ func (b *Admission) SetDefaultsWhereNeeded(replicaCount *int32, globalVPA *commo
 	b.Webhook.SetDefaultsWhereNeeded()
 
 	b.Replicas = common.SetDefault(b.Replicas, ptr.To(ptr.Deref(replicaCount, 1)))
+	if b.Autoscaling != nil {
+		b.Autoscaling.SetDefaultsWhereNeeded()
+	}
+
 	b.GPUSharing = common.SetDefault(b.GPUSharing, ptr.To(gpuSharingEnabledForMode(gpuSharingMode)))
 	b.QueueLabelSelector = common.SetDefault(b.QueueLabelSelector, ptr.To(false))
 	b.BlockNvidiaVisibleDevices = common.SetDefault(b.BlockNvidiaVisibleDevices, ptr.To(false))

kai/v1/admission/admission_test.go

@@ -56,4 +56,42 @@ var _ = Describe("Admission", func() {
 		Admission.SetDefaultsWhereNeeded(nil, nil, common.GpuSharingModeHamiCore)
 		Expect(*Admission.GPUSharing).To(BeFalse())
 	})
+	It("does not configure autoscaling by default", func(ctx context.Context) {
+		admission := &Admission{}
+
+		admission.SetDefaultsWhereNeeded(nil, nil, common.GpuSharingModeNonMemoryEnforced)
+
+		Expect(admission.Autoscaling).To(BeNil())
+	})
+
+	It("sets autoscaling defaults when configured", func(ctx context.Context) {
+		admission := &Admission{
+			Autoscaling: &Autoscaling{},
+		}
+
+		admission.SetDefaultsWhereNeeded(nil, nil, common.GpuSharingModeNonMemoryEnforced)
+
+		Expect(*admission.Autoscaling.Enabled).To(BeFalse())
+		Expect(admission.Autoscaling.MaxReplicas).To(BeNil())
+		Expect(admission.Autoscaling.TargetInFlightRequests).To(BeNil())
+		Expect(admission.Autoscaling.TargetCPUUtilizationPercentage).To(BeNil())
+	})
+
+	It("preserves explicit autoscaling configuration", func(ctx context.Context) {
+		admission := &Admission{
+			Autoscaling: &Autoscaling{
+				Enabled:                        ptr.To(true),
+				MaxReplicas:                    ptr.To(int32(5)),
+				TargetInFlightRequests:         ptr.To(int32(20)),
+				TargetCPUUtilizationPercentage: ptr.To(int32(80)),
+			},
+		}
+
+		admission.SetDefaultsWhereNeeded(nil, nil, common.GpuSharingModeNonMemoryEnforced)
+
+		Expect(*admission.Autoscaling.Enabled).To(BeTrue())
+		Expect(*admission.Autoscaling.MaxReplicas).To(Equal(int32(5)))
+		Expect(*admission.Autoscaling.TargetInFlightRequests).To(Equal(int32(20)))
+		Expect(*admission.Autoscaling.TargetCPUUtilizationPercentage).To(Equal(int32(80)))
+	})
 })