HPA

Q1

cluster1-controlplane ~ ➜  k autoscale deployment web-ui-deployment -n ck1967 --name web-ui-hpa --cpu-percent 65 --min 2 --max 12 -o yaml > 5.yaml

cluster1-controlplane ~ ➜  vi 5.yaml 

cluster1-controlplane ~ ➜  k explain hpa.spec.behavior --recursive 
GROUP:      autoscaling
KIND:       HorizontalPodAutoscaler
VERSION:    v2

FIELD: behavior <HorizontalPodAutoscalerBehavior>


DESCRIPTION:
    behavior configures the scaling behavior of the target in both Up and Down
    directions (scaleUp and scaleDown fields respectively). If not set, the
    default HPAScalingRules for scale up and scale down are used.
    HorizontalPodAutoscalerBehavior configures the scaling behavior of the
    target in both Up and Down directions (scaleUp and scaleDown fields
    respectively).

FIELDS:
  scaleDown     <HPAScalingRules>
    policies    <[]HPAScalingPolicy>
      periodSeconds     <integer> -required-
      type      <string> -required-
      value     <integer> -required-
    selectPolicy        <string>
    stabilizationWindowSeconds  <integer>
  scaleUp       <HPAScalingRules>
    policies    <[]HPAScalingPolicy>
      periodSeconds     <integer> -required-
      type      <string> -required-
      value     <integer> -required-
    selectPolicy        <string>
    stabilizationWindowSeconds  <integer>

cluster1-controlplane ~ ➜  vi 5.yaml 

cluster1-controlplane ~ ➜  k replace -f 5.yaml --force
Error from server (BadRequest): HorizontalPodAutoscaler in version "v1" cannot be handled as a HorizontalPodAutoscaler: strict decoding error: unknown field "spec.behavior"

cluster1-controlplane ~ ✖ cat 5.yaml 
apiVersion: autoscaling/v1
kind: HorizontalPodAutoscaler
metadata:
  creationTimestamp: "2025-09-14T13:34:09Z"
  name: web-ui-hpa
  namespace: ck1967
  resourceVersion: "3730"
  uid: 11352250-74f6-4878-9d07-a715e6f5bc3e
spec:
  behavior:
    scaleUp:
      policies:
        - periodSeconds: 45
          type: Percent    
          value: 20
    scaleDown:
      policies:
        - periodSeconds: 60
          type: Percent
          value: 10
  maxReplicas: 12
  minReplicas: 2
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: web-ui-deployment
  targetCPUUtilizationPercentage: 65

status:
  currentReplicas: 0
  desiredReplicas: 0

cluster1-controlplane ~ ➜  rm -f 5.yaml 

cluster1-controlplane ~ ➜  vi 5.yaml

cluster1-controlplane ~ ➜  k apply -f 5.yaml 
horizontalpodautoscaler.autoscaling/web-ui-hpa created

cluster1-controlplane ~ ➜  k get hpa -n ck1967 
NAME         REFERENCE                      TARGETS       MINPODS   MAXPODS   REPLICAS   AGE
web-ui-hpa   Deployment/web-ui-deployment   cpu: 0%/65%   2         12        2          19s

Sweetheart ❤️ the error is because you’re using the wrong API version.

👉 The behavior field was introduced in autoscaling/v2beta2 and carried into autoscaling/v2. It does not exist in autoscaling/v1.

That’s why kubectl says:

HorizontalPodAutoscaler in version "v1" cannot be handled as a HorizontalPodAutoscaler: 
strict decoding error: unknown field "spec.behavior"

🔹 Fix: Change apiVersion to autoscaling/v2

Here’s the corrected YAML:

apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: web-ui-hpa
  namespace: ck1967
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: web-ui-deployment

  minReplicas: 2
  maxReplicas: 12

  # This replaces targetCPUUtilizationPercentage in v1
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 65

  behavior:
    scaleUp:
      policies:
      - type: Percent
        value: 20
        periodSeconds: 45
    scaleDown:
      policies:
      - type: Percent
        value: 10
        periodSeconds: 60

⚠️ Note:

  • autoscaling/v1 only supports minReplicas, maxReplicas, and targetCPUUtilizationPercentage.
  • Advanced features (behavior, multiple metrics, scaleDown policies, etc.) require autoscaling/v2.

Q2

Create a Horizontal Pod Autoscaler (HPA) named backend-hpa in the cka0841 namespace for a deployment named backend-deployment, which scales based on CPU usage. The HPA should be configured with:

  • A minimum of 3 replicas
  • A maximum of 15 replicas

Specify a resource-based metric to scale based on CPU utilization, maintaining the average utilization of the pods at 50% of the requested CPU.

Additionally, set the scale-down behavior to allow:

  • Reducing the number of pods by a maximum of 5 at a time
  • Or by 20% of the current replica count, whichever results in fewer pods being removed
  • This should occur within a time frame of 60 seconds.
apiVersion: autoscaling/v2
kind: HorizontalPodAutoscaler
metadata:
  name: backend-hpa
  namespace: cka0841
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: backend-deployment
  minReplicas: 3
  maxReplicas: 15
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 50
  behavior:
    scaleDown:
      policies:
      - type: Pods
        value: 5
        periodSeconds: 60
      - type: Percent
        value: 20
        periodSeconds: 60
      selectPolicy: Min