[Feature]: Ability to disable LoadBalancer

[alistarle]

Explain problem to solve

I try to make Kamaji (Hosted Control Plane technology) to support Outscale provider, and then spawn control plane inside pod of a management cluster, and worker as Outscale VM.

For this, I need to disable the loadbalancer of the OscCluster resource as the control plane is already provisionned, so the outscale provider will only spawn workers.

I achieved this by juste disabling LoadBalancer of the OscCluster (Kamaji support a way to patch generic infrastructure provider). When this feature will be merged, I will add first class support of Outscale provider to Kamaji and write documentation about it.

Describe the solution you would like

Edit the OscCluster CRD to optionnaly disable the LoadBalancer (like the bastion feature flag), and rely on an externally managed LoadBalancer to create the OscMachine

Additional context

Goal is to support tooling like Kamaji to perform hosted control plane. I achieved to make Kamaji supporting Outscale Infrastructure by making this little tweak in the CRD. Example for the Openstack Provider in Kamaji docuementation: https://github.com/clastix/cluster-api-control-plane-provider-kamaji/blob/master/docs/providers-openstack.md?plain=1#L195

More information on Kamaji can be found here: https://kamaji.clastix.io/concepts/

Environment

- Kubernetes version: (use `kubectl version`): 1.33.1
- OS (e.g. from `/etc/os-release`): Ubuntu 22.04
- cluster-api-provider-outscale version: 0.4.0
- cluster-api version: 1.10.2
- Kubernetes Distribution: Kubeadm with Kamaji controlplane provider

[alistarle]

@jfbus wdyt of this ? Should I continue that way ?

[jfbus]

Kamaji looks interesting.

There are also issues with security group rules:

1. with inbound IP filtering activated, the public IP of the worker NAT must be dynamically added to the LB SG,
2. the public IP of the control plane needs to be authorized in the worker inbound rules.

An alternative way of solving the LB issue would be to implement load-balancer reuse, which would help with 1. (otherwise you would probably need to reuse a network with an existing NAT).

2. currently requires manual security group rules, we would need to configure the control plane public IP to be able to automatically configure CP -> W flows.

[jfbus]

• avoid replacing endpoint if already set by kamaji
• avoid creating subnets/SG for control-planes