📖 Add control plane machine count 1 warning

[dtzar]

Signed-off-by: David Tesar [email protected]

What this PR does / why we need it:
Fixes #3425

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[oscr]

/ok-to-test

[killianmuldoon]

Thanks for taking an interest in this @dtzar! However, having a controlplane-machine-count of 1 isn't the same as what's outlined in #3425 - that's about dropping support for standalone control-plane machines i.e. those not managed by a control plane provider.

There's an ongoing conversation about dropping support for this in 1.4 though. @dtzar it would be great help if you could find where in the book we might be pointing toward that use case and remove those instances to help drive that work forward.

[dtzar]

Thanks for the feedback. So you're saying dropping support for deploying any number of control plane machines which are not managed by a provider? Perhaps you could link to one or more places in documentation where this is referenced?

[killianmuldoon]

So you're saying dropping support for deploying any number of control plane machines which are not managed by a provider

Exactly - I don't think CAPI should enforce specific deployment scenarios like e.g. number of CP nodes in a cluster, but currently support is built-in for 'standalone' control planes which, in general, pre-existed the Control Plane providers.

I'm not sure how many places in the documentation explicitly supports the use case but there is this in staging-use-cases.md:

• As an operator, given that I have a management cluster and a pre-existing control plane, I would like to manage the lifecycle of a group of worker nodes without managing the control plane those nodes join.

I think we need the community discussion on deprecating this case to move forward before actually making any changes.

[dtzar]

Ok, I provided my feedback on migrating the staging-use-cases document all together on your issue.