Filter attachment(s) based on watch

[AmitKumarDas]

Motivation

Metac's GenericController introduces the concept of watch and attachments. One can think of watch as the resource that is observed via Informer and attachments as the resources that should be fetched/listed via Lister based invocations. With this concept in mind, how do we filter out the attachments that belong to the particular watch. Note that GenericController should list the attachments that may or may not be owned by the watch resource. In order to keep the attachments arbitrary and still if required filter them based on watch is what this issue is all about.

Possible Solution

This is the current GenericController that watches kind:Storage and returns the watch object along with all the PVCs and PVs.

spec:
  watch:
    apiVersion: core/v1alpha1
    resource: storages
  attachments:
  - apiVersion: storage/v1
    resource: persistentvolumeclaims
  - apiVersion: storage/v1
    resource: persistentvolumes

This is the suggested GenericController that watches kind:Storage and returns specific PVCs & PVs. In this particular spec, PVCs that are owned by Storage and PVs that have the Storage name as its annotation are selected.

spec:
  watch:
    apiVersion: core/v1alpha1
    resource: storages
  attachments:
  - apiVersion: storage/v1
    resource: persistentvolumeclaims
    matchesWatch:
      expressions:
      - operator: OwnerIsWatch # Does watch own this PVC?
  - apiVersion: storage/v1
    resource: persistentvolumes
    matchesWatch:
      expressions:
      - key: ddp.openebs.io/storage-name # a key in PV's annotations
        operator: AnnotationIsWatchName # Is annotation value the name of Watch

[AmitKumarDas]

Some of the schema definitions that can be referred to are:

• NodeSelector in https://github.com/kubernetes/kubernetes/blob/master/staging/src/k8s.io/api/core/v1/types.go

[AmitKumarDas]

#51

[AmitKumarDas]

closing this as part of following commits:
https://github.com/AmitKumarDas/metac/issues?q=label%3Aselect+is%3Aclosed