[IMPROVEMENT] UI should refuse to attach strict-local volume to the wrong node

[ejweber]

Is your improvement request related to a feature? Please describe (👍 if you like this request)

Off the top of my head, I'm not sure how easy this request is to implement (probably not too bad), but the existing behavior is a bit weird:

• Create a strict-local volume in the UI.
• Attach it to a node in the UI.
• Detach if from the node in the UI.
• Attach it to a different node in the UI.

This is not legal, and indeed, longhorn-manager logs errors and refuses to complete the operation.

[longhorn-manager-m9vhl] time="2024-05-10T20:02:03Z" level=error msg="Failed to sync Longhorn VolumeAttachment" func=controller.handleReconcileErrorLogging file="utils.go:67" LonghornVolumeAttachment=longhorn-system/test controller=longhorn-volume-attachment error="longhorn-volume-attachment: failed to sync VolumeAttachment longhorn-system/test: admission webhook \"validator.longhorn.io\" denied the request: failed to check if strict-local volume test and its replica are on the same node: moving a strict-local volume test to another node is not supported" node=eweber-v126-worker-9c1451b4-kgxdq
[longhorn-manager-mmjh9] time="2024-05-10T20:02:03Z" level=warning msg="Rejected operation: Request (user: system:serviceaccount:longhorn-system:longhorn-service-account, longhorn.io/v1beta2, Kind=Volume, namespace: longhorn-system, name: test, operation: UPDATE)" func="admission.(*Handler).admit" file="admission.go:106" error="failed to check if strict-local volume test and its replica are on the same node: moving a strict-local volume test to another node is not supported" service=admissionWebhook```

However, this message is coming from the attach/detach controller. There is already an attachment ticket in the corresponding volumeattachment.longhorn.io CR, and the attach API call returned successful to the UI.

  spec:
    attachmentTickets:
      longhorn-ui:
        generation: 0
        id: longhorn-ui
        nodeID: eweber-v126-worker-9c1451b4-6464j
        parameters:
          disableFrontend: "false"
          lastAttachedBy: ""
        type: longhorn-api
    volume: test
  status:
    attachmentTicketStatuses:
      longhorn-ui:
        conditions:
        - lastProbeTime: ""
          lastTransitionTime: "2024-05-10T19:44:31Z"
          message: ""
          reason: ""
          status: "False"
          type: Satisfied
        generation: 0
        id: longhorn-ui
        satisfied: false

There is no error in the UI, but the volume is not (and will not be) attached.

Describe the solution you'd like

It would be better to fail obviously at an upper layer so the UI is aware. Maybe the VolumeManager.Attach method can check for this situation and return an error instead of creating the volumeattachment.longhorn.io?