📖 Adds a cluster controller document

[chuckha]

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

What this PR does / why we need it:
This PR adds some formalization around what the cluster controller is responsible for and the contracts it defines within its code.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Related to #1370

[vincepri]

The filed name should be value and the content should be a base64 encoded kubeconfig

[chuckha]

Do you think it's worth adding that check to ClusterReconciler.reconcileKubeconfigOr do you think it's enough to look for a properly named secret? Right now that function is only checking for the existence of the secret.

But yes, this is the expected value, I'll definitely add these changes, thanks

[vincepri]

It should definitely error today if the value isn't found, I can dig up the code later

[chuckha]

This only checks for the existence of the secret, not the contents.

cluster-api/controllers/cluster_controller_phases.go

Lines 181 to 188 in 2c4cbfa

	_, err := secret.Get(r.Client, cluster, secret.Kubeconfig)
	switch {
	case apierrors.IsNotFound(err):
	return kubeconfig.CreateSecret(ctx, r.Client, cluster)
	case err != nil:
	return errors.Wrapf(err, "failed to retrieve Kubeconfig Secret for Cluster %q in namespace %q", cluster.Name, cluster.Namespace)
	}
	return nil

[vincepri]

/approve
/assign @detiber

[k8s-ci-robot]

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[detiber]

Should ErrorMessage and ErrorReason also be listed here?

[chuckha]

Ah indeed it should

[chuckha]

Upon further inspection these are not required, but I will add another section outlining how these are used.

[chuckha]

@vincepri @detiber I believe this is good to go pending any more feedback. Will update the machine controller document in a similar way

[detiber]

/lgtm

I think we can iterate on any additional changes after merge.