ClusterClass MachinePool implementation is probably not able to rollout BootstrapConfig changes. #10496
Description
Quoting from a different issue:
Can you please summarize what a user would have to do to rollout a change to a KubeadmConfig with a reguar cluster (not using ClusterClass). Is it as simple as modifying the KubeadmConfig object that is linked in a MachinePool directly?
Change MachinePool.spec.template.spec.bootstrap.configRef.name and the KubeadmConfig.spec changes will be reconciled.
In practice, that means a user's KubeadmConfig.metadata.name should be suffixed with a hash (or increasing number) when making changes, and the reference in the MachinePool object gets changed to this new KubeadmConfig name.
#8858 (comment)
The ClusterClass MachinePool implementation today uses one single BootstrapConfig / KubeadmConfig object for a MachinePool and just continuously patches it in-place to rollout changes.
Based on #8858 this is not enough, it seems to be required to rotate the BootstrapConfig object (create a new one + update the ref in MachinePool).
Someone would need to confirm if my observation is correct.
Furthermore I don't know if there is a documented contract as of today for MachinePools how BootstrapConfigs are supposed to be rolled out. I also don't know if MachinePools behave the same across providers today.
So my tl;dr:
- ClusterClass can probably not rollout BootstrapConfig changes for MachinePools today
- We need a documented contract on how BootstrapConfig rollouts are supposed to work with MachinePools