Update to primaryScalerReplicas is ignored if no other changes inside the canary

[yarosq]

Describe the bug

Updates to autoscalerRef.primaryScalerReplicas are ignored

  autoscalerRef:
    apiVersion: autoscaling/v2
    kind: HorizontalPodAutoscaler
    name: service-deployment
    primaryScalerReplicas:
      maxReplicas: 4
      minReplicas: 4

To Reproduce

1. Create canary with autoscalerRef defined

  autoscalerRef:
    apiVersion: autoscaling/v2
    kind: HorizontalPodAutoscaler
    name: service-deployment
    primaryScalerReplicas:
      maxReplicas: 2
      minReplicas: 2

2. Update maxReplicas/minReplicas

  autoscalerRef:
    apiVersion: autoscaling/v2
    kind: HorizontalPodAutoscaler
    name: service-deployment
    primaryScalerReplicas:
      maxReplicas: 4
      minReplicas: 4

-->

Result: Primary hpa is not updated and only 2 pod instance are running

kubectl get hpa service-deployment-primary --template='.spec.maxReplicas: {{.spec.maxReplicas}}{{"\n"}}.spec.minReplicas: {{.spec.minReplicas}}'
.spec.maxReplicas: 2
.spec.minReplicas: 2

Expected behavior

Primary hpa resource should be updated and primary pods scaled to 4 instances

Workaround

• we can patch the canary with pod annotation but this will trigger the canary release which is not ideal.
• we can update primary hpa manually but I expect this to happens automatically

Additional context

• Flagger version: 1.35.0
• Kubernetes version: 1.27
• Service Mesh provider: Linkerd