freezer backup clean snapshot error

[AnnieLiu]

Cinder's Backend is CEPH.

backup cinder
      1. cinder snapshot
      2. create volume by snapshot
      3. copy volume to image
      4. save image to local
      5. delete volume snap (failed)
      6. delete volume
      7. delete image

[code]
    def backup_cinder_by_glance(self, volume_id):
        """
        Implements cinder backup:
            1) Gets a stream of the image from glance
            2) Stores resulted image to the swift as multipart object

        :param volume_id: id of volume for backup
        """
        ......

        LOG.debug("Deleting temporary snapshot")
        client_manager.clean_snapshot(snapshot)
        LOG.debug("Deleting temporary volume")
        cinder.volumes.delete(copied_volume)
        LOG.debug("Deleting temporary image")
        client_manager.get_glance().images.delete(image.id)

[comment]
Since the volume depends on the snapshot (it's created by snapshot with clone on CEPH, without flatten), deleting snapshot can't be done before volume is deleted.

[cinder-volume.log]
2023-03-20 17:32:35.800 34 ERROR cinder.volume.manager [req-d849f7ff-b8fa-4ca0-ad80-42298e87217f req-89e993fc-7837-451b-aa27-d72694a4aa1d@global_request_id 5ca52b5e65df4d879dd490afa350a3f0 76e23046831943bba571f0e3ea432182 - default default] Delete snapshot failed, due to snapshot busy.: SnapshotIsBusy: deleting snapshot snapshot-a540413c-72a9-4cde-8bea-a29b2ce7a012 that has dependent volumes

[cinder-volume.log]
2023-03-27 11:59:19.145 34 ERROR cinder.volume.manager [req-39f7e290-29f3-4e5d-b9c2-d6e96867ed51 req-f552a927-f882-48d0-9809-564acb73e121@global_request_id 5ca52b5e65df4d879dd490afa350a3f0 76e23046831943bba571f0e3ea432182 - default default] Delete snapshot failed, due to snapshot busy.: SnapshotIsBusy: deleting snapshot snapshot-561e441f-7e02-4f30-92b4-f0b00cacdcac that has dependent volumes

[Improvement Suggestion]
(delete temporary volume at first)
  delete volume => delete image => delete snapshot