Migrating ELB to NLB load balancers and immutable DNS records

[thefirstofthe300]

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/kind feature

Describe the solution you'd like I'm attempting to migrate our existing clusters off ELBs to NLBs for a few reasons, one of them being the ability to privatize intra-cluster traffic. I've brought my own load balancer for both the ELB and the NLB to the party; however, switching between the NLB and the ELB isn't as simple as flipping the spec/controlPlaneLoadBalancer/loadBalancerType switch on the AWS cluster resource due to the this line and this line causing the AWS cluster to fail update validation. AFAICT, everything else worked properly since CAPA registered the control plane instances with the load balancer. All I think I need to get this migration done is to force update that DNS name. One question I do have is if it makes sense to set that value using the NLB DNS record if I am setting my own DNS record in the KubeadmControlPlaneTemplate in /spec/template/spec/kubeadmConfigSpec/clusterConfiguration/controlPlaneEndpoint? I suppose that value isn't ever known to CAPA so it'd be impossible to know ahead of time without explicit configuration. Maybe instead, the DNS record shouldn't be immutable in the case that the LB is rebuilt for whatever reason?

Environment:

• Cluster-api-provider-aws version: v2.3.1
• Kubernetes version: (use kubectl version):

Server Version: version.Info{Major:"1", Minor:"28", GitVersion:"v1.28.3", GitCommit:"a8a1abc25cad87333840cd7d54be2efaf31a3177", GitTreeState:"clean", BuildDate:"2023-10-18T11:33:18Z", GoVersion:"go1.20.10", Compiler:"gc", Platform:"linux/amd64"}

• OS (e.g. from /etc/os-release): Flatcar

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@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

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• After 90d of inactivity, lifecycle/stale is applied
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