** Also affects: nova/pike
Importance: Undecided
Status: New
** Also affects: nova/rocky
Importance: Undecided
Status: New
** Also affects: nova/stein
Importance: Undecided
Status: New
** Also affects: nova/queens
Importance: Undecided
Status: New
** No longer affects: nova/pike
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https://bugs.launchpad.net/bugs/1653953
Title:
Unable to remove snapshots after an instance is unshelved when using
the rbd imagebackend
Status in OpenStack Compute (nova):
In Progress
Status in OpenStack Compute (nova) queens series:
New
Status in OpenStack Compute (nova) rocky series:
New
Status in OpenStack Compute (nova) stein series:
New
Bug description:
Description
===========
I'm not entirely convinced that this is a bug but wanted to document
and discuss this upstream.
When using the rbd imagebackend, snapshots used to shelve an instance
cannot be removed after unshelving as they are cloned and as a result
are now the parents of the recreated instance disks.
This is in line with the behaviour of the imagebackend when initially
spawning an instance from an image but has caused confusion for
operators downstream who assume that the snapshot can be removed once
the instance has been unshelved.
We could flatten the instance disk when spawning during an unshelve
but to do so would mean extending the imagebackend to handle yet
another corner case for rbd.
Steps to reproduce
==================
$ nova boot --image cirros-raw --flavor 1 test-shelve
[..]
$ nova shelve test-shelve
[..]
$ nova unshelve test-shelve
[..]
$ sudo rbd -p vms ls -l
NAME SIZE PARENT
FMT PROT LOCK
4c843671-879d-4ba6-b4e8-8eefdced5393_disk 1024M
images/df96af36-5a97-4f47-a79f-f3f3c85a21d9@snap 2
$ glance image-delete df96af36-5a97-4f47-a79f-f3f3c85a21d9
Unable to delete image 'df96af36-5a97-4f47-a79f-f3f3c85a21d9' because it is
in use.
We can easily workaround this by manually flattening the instance disk
:
$ nova stop test-shelve
$ sudo rbd -p vms flatten 4c843671-879d-4ba6-b4e8-8eefdced5393_disk
Image flatten: 100% complete...done.
$ nova start test-shelve
$ glance image-delete df96af36-5a97-4f47-a79f-f3f3c85a21d9
Expected result
===============
Able to remove the shelved snapshot from Glance after unshelve.
Actual result
=============
Unable to remove the shelved snapshot from Glance after unshelve.
Environment
===========
1. Exact version of OpenStack you are running. See the following
list for all releases: http://docs.openstack.org/releases/
$ pwd
/opt/stack/nova
$ git rev-parse HEAD
d768bfa2c2fb774154a5268f58b28537f7b39f69
2. Which hypervisor did you use?
(For example: Libvirt + KVM, Libvirt + XEN, Hyper-V, PowerKVM, ...)
What's the version of that?
libvirt + kvm
2. Which storage type did you use?
(For example: Ceph, LVM, GPFS, ...)
What's the version of that?
ceph
3. Which networking type did you use?
(For example: nova-network, Neutron with OpenVSwitch, ...)
N/A
Logs & Configs
==============
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