Namespace-scoped operators

[nolar]

Current Behaviour

Currently, --namespace= option is used only to limit the watch-event to the objects belonging to that namespace, and ignoring objects in other namespaces.

However, the framework continues to use the cluster-wide watching calls, and cluster-wide peering objects. The peering objects are now cluster-scoped by definition (in CRD), and there are no namespace-scoped peering objects at all.

Expected behaviour

As an operator developer, if I provide --namespace=something, I expect that the operator limits all its activities to that namespace only, and does not even request for the cluster-wide objects/queries — as they can be e.g. restricted by the permissions.

If I provide --namespace=something --peering=somepeering, I expect that the namespace-scoped peering object kind is used, not the cluster-scoped one.

Use-cases

The intended use-case 1: If an operator is a part of the application's deployment, and there are few instances of the same application deployed with different versions, but isolated by the namespaces. As a particular example: running a production, staging, and maybe experimental operators of the same application in different namespaces.

The intended use-case 2: Running in a cluster with strict RBAC rules, with no access to the cluster objects, restricted to one namespace only.

Steps to Reproduce the Problem

1. Create a RBAC service account with only the namespace permissions.
2. Deploy any of the example operators with --namespace=default (or any other namespace).
3. Observe how it fails on api.list_cluster_custom_object() (in queueing.py/watching.py).
   • for kopfexamples
   • for kopfpeerings

Acceptance Criteria

• Served objects:
  • with --namespace=, it uses the namespace-scoped watching api.list_namespaced_custom_object()
  • with no --namespace=, it uses the cluster-scoped watching api.list_cluster_custom_object()
• Peering objects:
  • KopfPeering is separated to ClusterKopfPeering & KopfPeering or NamespacedKopfPeering (keep backward compatibility if possible, but align with the existing convention of Role/ClusterRole, etc.)
  • with --namespace=, the namespace-scoped peering object is used.
  • with no --namespace=, the cluster-scoped peering object is used.
  • --peering= option only specifies the peering name, but not the listing/watching mechanics.
• Documentation:
  • RBAC configuration and deployment pattern.
  • CLI reference page.
  • Peering page.
  • A new page for cluster-vs-namespace separation ("Features" section).
• Tests.