Error when deleting a volume with snapshots not surfaced well

[Gabriel Hurley]

It is illegal to delete a volume which has "dependent" snapshots; the snapshots must be deleted first. However, this message is not surfaced to the user leaving them with no explanation why the volume can't be deleted.

Sadly, there's no data returned by the API to indicate this fact *before* attempting the deletion, so I'm not sure what the best solution is.

[Tihomir Trifonov (ttrifonov)]

It is interesting - the Volume object has a property 'snapshot_id' which is None, but the volume has snapshot. If Nova can somehow populate this with the snapshot id, we can hide the 'Delete' action for these volumes...

[Tihomir Trifonov (ttrifonov)]

Actually the snapshot_id field means that the volume is created from a snapshot..
As I see when executing 'lvdisplay' :

  LV Name /dev/n-volumes/volume-528b8d8d-8067-436b-8677-3892369dce83
  VG Name n-volumes
  LV UUID gltzr2-2bWw-4vnV-CS4h-OICa-dlab-naKik2
  LV Write Access read/write
  LV snapshot status source of
                         /dev/n-volumes/_snapshot-6863b9ff-3604-4966-83cf-c7fbf73ee056 [active]

There is a flag that the volume has an active snapshot. But it seems nova is using a higher-level driver - tgtadm to load volume data, and this flag is not available there.

Maybe it would be nice if the volume metadata is being updated with a flag when a snapshot is created/removed, and this flag to be passed...

One solution is to check first if there is a snapshot with volume_id == vol_id of the volume to be deleted, and to show warning/error message before the actual delete attempt.
Or just to catch the exception and show a hint what the reason could be ..

[Tihomir Trifonov (ttrifonov)]

Here are 2 possible solutions, but none of them is perfect..

1. Load all snapshost on page load and allow the 'Delete' action only of there is no Snapshot with the specified volume id.
  Pros - we will hide 'Delete' button for volumes that cannot be deleted.
  Cons - when trying to delete a volume using the Table 'Delete' Action and 'select-all' checkbox, an error will be displayed: "You do not have permissions to delete volume: xxxx', which is misleading a bit...

2. Catch the exception on 'delete()' and process it to see if it is caused by an existing snapshot.
  Pros - this works on delete, no need to pre-load anything.
  Cons - needs some refactoring for BatchAction class, as it ignores the exception error. It might be fixed to work with 2 errors, but.. again not the perfect solution.

[Gabriel Hurley (gabriel-hurley)]

I'd go with option 2 as a temporary fix. We've special-cased a few other exceptions in this manner.

[Gabriel Hurley (gabriel-hurley)]

Moving to RC1 since it's not urgent.

[Gabriel Hurley (gabriel-hurley)]

This can now be addressed in the larger context of a fix for https://bugs.launchpad.net/horizon/+bug/1037241

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/12417

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/12417
Committed: http://github.com/openstack/horizon/commit/ceb22f13b901dced411afc1b9174b1514aee18b7
Submitter: Jenkins
Branch: master

commit ceb22f13b901dced411afc1b9174b1514aee18b7
Author: Tihomir Trifonov <email address hidden>
Date: Wed Sep 5 15:10:10 2012 +0300

    Adds a method for overriding specific API messages.

    Also provides a specific error message for dependent snapshots
    during volume deletion.

    Fixes bug 1037241. Fixes bug 1020326.

    Change-Id: I40e5f537bc1806ec97c21f3eeea1d74beca04250