[OpenStack Mitaka -> Nova/Ceph] fails to delete snapshots when they are used to create instances

[Nicolas Peter Lane]

The bug happens in OpenStack Mitaka from Mirantis Fuel 9.2, we didn't see any bug reported in Mitaka or earlier versions of OpenStack regarding it.

We're currently almost certain the culprit is Nova.

How to reproduce the bug:

1) Create an instance (I'll label it i_1)
2) Create a snapshot from this instance (I'll label it s_1)
3) From this snapshot create another instance (I'll label it i_2)
4) Delete this new instance i_2
4) Now, try to delete the snapshot s_1

The error will inform you that it could not delete it.
Which in turn causes your storage to have a lot of trash :(.

Details:

It seems to be caused due to Nova failing to tell Ceph to delete the disk of i_2.
Hence, the snapshot fails to be deleted because of its discs's dependencies.

Workaround found:
Manually delete the disks using Ceph and then delete the snapshot.

Log attached below.

[Oleksiy Molchanov (omolchanov)]

Nicolas, I was not able to reproduce this. Can you try to reproduce this and share full diagnostic snapshot.