[Feature request] Add support for custom path for snapshots

[smuda]

Is your feature request related to a problem?/Why is this needed
When creating snapshots they are created at the NFS root, with names that is unclear what volume claim that is the origin of the snapshot. It's also problematic after hundreds of snapshots to have them all in the same folder as the volumes.

Describe the solution you'd like in detail
For the volumes I can specify the subpath in StorageClass.parameters.subdir with templating, for example ${pvc.metadata.namespace}/pvc-${pvc.metadata.name}

I'd propose using the same model for VolumeSnapshotClass.parameters.subdir with support for at least vs.metadata.name, vs.metadata.namespace and vs.spec.source.persistentVolumeClaimName.

[andyzhangx]

@smuda the *.tar.gz already contains the pv name, check below logs, is that enough?

[pod/csi-test-controller-9784fb589-nprbv/nfs] I1213 02:44:38.584541       1 utils.go:108] GRPC call: /csi.v1.Controller/CreateSnapshot
[pod/csi-test-controller-9784fb589-nprbv/nfs] I1213 02:44:38.584560       1 utils.go:109] GRPC request: {"name":"snapshot-a56cdc8b-a0e2-4f46-b3a0-916ffed068eb","source_volume_id":"nfs-server.default.svc.cluster.local##pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac##"}
[pod/csi-test-controller-9784fb589-nprbv/nfs] I1213 02:44:38.618522       1 nodeserver.go:144] volume(nfs-server.default.svc.cluster.local##pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac##) mount nfs-server.default.svc.cluster.local:/ on /tmp/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac succeeded
[pod/csi-test-controller-9784fb589-nprbv/nfs] I1213 02:44:38.618649       1 controllerserver.go:357] archiving /tmp/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac -> /tmp/snapshot-a56cdc8b-a0e2-4f46-b3a0-916ffed068eb/snapshot-a56cdc8b-a0e2-4f46-b3a0-916ffed068eb/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac.tar.gz
[pod/csi-test-controller-9784fb589-nprbv/nfs] I1213 02:44:38.622663       1 controllerserver.go:362] archived /tmp/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac -> /tmp/snapshot-a56cdc8b-a0e2-4f46-b3a0-916ffed068eb/snapshot-a56cdc8b-a0e2-4f46-b3a0-916ffed068eb/pvc-9e6bdd5a-c6c0-466a-b0b5-9b6cbf84a0ac.tar.gz

[smuda]

Only as long as the cluster is healthy :-)

So the PVC we create have a nice, understandable name which, especially in the context of a namespace, makes sense:

NAME                         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS
alert-pg                     Bound    pvc-cc3f3d08-f0ef-4769-a9c7-bf0901b108eb   5Gi        RWO            nfs-csi       
...

But the automatically created PVs does not get understandable names:

NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM                                             STORAGECLASS   REASON 
pvc-cc3f3d08-f0ef-4769-a9c7-bf0901b108eb   5Gi        RWO            Delete           Bound    bd/alert-pg                                       nfs-csi
...

So even though the PV name ("pvc-cc3f3d08-f0ef-4769-a9c7-bf0901b108eb") is included in the path, it doesn't really tell me anything (not even namespace) when trying to restore the PVs after the cluster has gone "boom".

In my context, I'd like to create the snapshots inside a directory for the namespace with a name taken from the PVC, and of course some kind of uid (or date/time?) to distinguish between the snapshots, for example:
subdir="snapshots/${vs.metadata.namespace}/${vs.spec.source.persistentVolumeClaimName}"

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@k8s-triage-robot: Closing this issue, marking it as "Not Planned".

In response to this:

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

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/close not-planned

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