Document and add validation on enable_cri_dockerd option

[felipe-colussi]

Issue: #404

Problem

K8s 1.24+ needs enable_cri_dockerd to be set to true for clusters to successfully provision.

Solution

We cant do that change.

a) change the default value of enable_cri_dockerd to true

This would change the behavior of cluster using k8s 1.23 or less.

b) Set enable_cri_dockerd to true during execution time:

This would generate inconsistency on terraform plans and would result on the resource being applied every single time.

Add to the docs that the user need to change the value of the field.

Also added a validation function on the Expander that is used to create/update the cluster.

This can't be a "ValidationFunc" from terraform as it depends on 2 fields.

Testing

Added a validation for the function that checks the k8s version

Engineering Testing

Manual Testing

Automated Testing

• Test types added/modified:

  • None

• If "None" - Reason:
  Change to the docs.

Summary:

QA Testing Considerations

Regressions Considerations

There is no regression, this is a doc only

[a-blender]

Note: There was significant discussion around the decision for the RKE enable_cri_dockerd option and this was the simplest solution instead of handling the value in an unexpected way on the backend based on the version of the cluster. Once k8s 1.23 is deprecated, we will update the default to true and users can provision RKE clusters without manually setting the value.

[a-blender]

Can you add validation for the provider to error out if a user sets false on a 1.24+ cluster? Either in a ValidateFunc or if you don't have access to the k8s version, perhaps here

terraform-provider-rke/rke/structure_rke_cluster.go

Lines 91 to 93 in 1a25755

	if _, ok := d.Get("enable_cri_dockerd").(bool); ok && in.EnableCRIDockerd != nil {
	d.Set("enable_cri_dockerd", *in.EnableCRIDockerd)
	}

Thank you @jiaqiluo for the feedback!

[a-blender]

Lgtm now, please squash on merge