✨ implement failure domain picking

[chuckha]

Signed-off-by: Chuck Ha chuckh@vmware.com

What this PR does / why we need it:
This PR adds failure domain picking to the KubeadmControlPlane. There is no change to logic if failure domain is not defined. If a failure domain is defined then the KubeadmControlPlane controller will evenly distribute machines across all defined failure domains.

This is a naive approach. Please see #2131 for more details.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #2131
Related to #1756

/assign @detiber

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[detiber]

@chuckha since this PR is marked as Fixing #2131, do we need another issue to track setting the Failure domain for a Machine post-creation if a provider later adds failure domain support?

[chuckha]

@chuckha since this PR is marked as Fixing #2131, do we need another issue to track setting the Failure domain for a Machine post-creation if a provider later adds failure domain support?

This is really two issues.

One requires documentation for infrastructure providers saying that if they decide to add support for failure domains then the provider also needs to update the InfraMachines with their existing failure domain as the machine-controller in cluster-api would have no way to figure out which failure domain the machine lives in.

The second part is having the machine controller copy the infra machine failure domain into the machine.

I'll open these issues later on.

[detiber]

This is really two issues.

One requires documentation for infrastructure providers saying that if they decide to add support for failure domains then the provider also needs to update the InfraMachines with their existing failure domain as the machine-controller in cluster-api would have no way to figure out which failure domain the machine lives in.

The second part is having the machine controller copy the infra machine failure domain into the machine.

I'll open these issues later on.

sgtm, just wanted to make sure we don't drop tracking for it :)

[detiber]

/lgtm
/assign @vincepri

[vincepri]

/approve