remove_export needs an API to prevent dangling exports

[Scott DAngelo]

Nova has a command 'shelve' that allows a user to snapshot an instance and remove it from the hypervisor. When the instance is unshelved, it can come back on another Nova compute host. IF there is a volume attached during this process, the cinder-volume target for the volume will still exist and there is no way to delete it. Nova should not call volume_api.detach for this process because we want the volume to still be 'in-use' and 'attached' in the Cinder DB.
The proposed way to solve this is to have an API to call remove_export so that the target can be removed.

[Matt Riedemann (mriedem)]

This is most likely going to require a cinder spec if there is a new API, so a bug by itself isn't going to cut it.

This came up here: https://review.openstack.org/#/c/257275/

[Sean McGinnis (sean-mcginnis)]

Unassigning due to no activity.

[Sean McGinnis (sean-mcginnis)]

May be addressed by the new attach/detach APIs being worked on by John.

[Matt Riedemann (mriedem)]

Could terminate_connection just remove the export? Then we wouldn't need a new API. The only issue is if that's a backward incompatible change in how terminate_connection is expected to behave.

[Matt Riedemann (mriedem)]

Discussed this at the Pike PTG, notes are here:

https://etherpad.openstack.org/p/cinder-ptg-queens

We're going to restore nova change https://review.openstack.org/#/c/257275/ for fixing this for existing attachments and the new style code that relies on Cinder API 3.27 and 3.44 will fix this for new style attachments: https://review.openstack.org/330285