fix(kuma-cp): mesh delete validation

[lobkovilya]

Summary

PR https://github.com/Kong/kuma/pull/742 introduced 2 owners for Dataplane resource - Pod and Mesh. It means Dataplane will be deleted only when both Pod and Mesh are deleted. That leads to wrong behavior during scaling up and down. Offline dps are owned by Mesh and hence aren't deleted.

This PR leaves only 1 owner for Dataplane - Pod. Also this PR adds validation of Mesh during DELETE. Now it is prohibited to delete Mesh when there are any Dataplane attached to that Mesh exists.

Full changelog

• Delete Mesh owner of the Dataplane
• Validation of Mesh during DELETE

[jakubdyszkiewicz]

This seems to be implemented only for K8S, what about Universal?

Should we check existence of Dataplane or should we check if Dataplane is online?

[lobkovilya]

This seems to be implemented only for K8S, what about Universal?

On Universal Dataplanes are owned by Mesh, there are no Pods, so Dataplanes will be deleted with Mesh as it was before.

Should we check existence of Dataplane

To be honest I didn't get that question, I allow to delete Mesh only if there are no dataplanes at all.

should we check if Dataplane is online?

That's a good point, I also thought about it. On k8s deleting of the Pod in 100% cases leads to deleting of the Dataplane resource. So if we observe "offline" state that probably occurred because of some underlying network connectivity problem or restarting of the container, anyway Pod exists and eventually might become "online" again. So probably if only "offline" dataplanes remain we also shouldn't remove the dp resource. Does it make sense?

[nickolaev]

Looks good to me.