elbv2: controller removes targetGroupRef upon sync

[blowfishpro]

Describe the bug

When load balancer rule actions point to a target group via targetGroupRef, the controller will successfully resolve the reference but then remove the targetGroupRef from the spec, causing drift when using diffing tools or GitOps workflows.

Looks very similar to #2361 which references ECS but is not tagged with a specific service, feel free to close this if you'd rather keep everything under that one issue.

Watching the object diffs it looks like the resource briefly gets the ACK.ReferencesResolved=True condition but then it gets removed immediately.

I tried both spec.actions[].targetGroupRef and spec.actions[].forwardConfig.targetGroups[].targetGroupRef and see the same behavior.

Steps to reproduce

• Create a load balancer Rule that references a target group via spec.actions[].targetGroupRef and spec.actions[].forwardConfig.targetGroups[].targetGroupRef
• Let it get reconciled
• Look at the state of the API object

Expected outcome

targetGroupRef should not be removed. Ideally user-supplied fields in the resource spec should not be modified by the controller.

Environment

• Kubernetes version: 1.32
• Using EKS yes
• AWS service targeted: ELBv2
• Controller version: 1.1.2

[github-actions]

Hello @blowfishpro 👋 Thank you for opening an issue in ACK! A maintainer will triage this issue soon.

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[michaelhtm]

Hey @blowfishpro, I have a proposed solution to this issue, but it may take some time to get consensus on the best solution.
A recommended workaround for these types of issues is kro.

Here is an example of how you can use it with AWS resources: https://github.com/kubernetes-sigs/kro/blob/main/examples/aws/ack-eks-cluster/eks-cluster.yaml
hope that helps!