** Description changed:
******* SRU TEMPLATE AT THE BOTTOM **********
Affects: bobcat and older
A race condition when deleting cloned volumes at the same time as their
parent results in the volumes in error_deleting state. The reason it
happens is because the code that looks for the parent in [3] may find
the original volume or the "<volume>.deleted" renamed volume if the
parent has been marked for deletion. The race happens because by running
the deletion of both the parent and the child at the same time, the
child may see the parent volume before it is marked for deletion, and
then in [4] it fails to find it again because it is gone (renamed to
"<volume>.deleted").
Steps to reproduce:
1) openstack volume create --size 1 v1
Wait for volume to be create and available
2) for i in {1..9}; do openstack volume create d$i --source v1 --size
1;done
Wait for all volumes to be created and available
3) openstack volume delete $(openstack volume list --format value -c ID
| sort | xargs)
Some volumes may be in error_deleting state.
Workaround: Reset volume state and try to delete again.
Solutions:
a) The issue does not happen in caracal+ because of commit [1] which
refactors the code. I tried to reproduce in Caracal with 50 volumes,
including grandparent volumes, and I couldn't. If we could backport this
fix as far back as Yoga this would address the problem for our users.
b) A single line of code in [2] can address the problem in bobcat and
older releases by adding a retry:
@utils.retry(rbd.ImageNotFound, 2)
def delete_volume(self, volume: Volume) -> None:
The retry basically causes the ImageNotFound exception thrown at [4] to
retry the delete_volume function, which will then find the
"<volume>.deleted" at [3], solving the race condition. It is simpler
than adding something more complex directly at [4] where the error
happens.
[1]
https://github.com/openstack/cinder/commit/1a675c9aa178c6d9c6ed10fd98f086c46d350d3f
[2]
https://github.com/openstack/cinder/blob/5b3717f8bfa69c142778ffeabfc4ab91f1f23581/cinder/volume/drivers/rbd.py#L1371
[3]
https://github.com/openstack/cinder/blob/5b3717f8bfa69c142778ffeabfc4ab91f1f23581/cinder/volume/drivers/rbd.py#L1401
[4]
https://github.com/openstack/cinder/blob/5b3717f8bfa69c142778ffeabfc4ab91f1f23581/cinder/volume/drivers/rbd.py#L1337
-
===================================================
SRU TEMPLATE
============
[Impact]
Due to a race condition, attempting to delete multiple volumes where
among them there is a parent and a child can result in one or more
volumes being stuck in error_deleting. The reason is because the childs
get updated as the parent is deleted, and if the code had already
started deleting the child then the reference changes halfway through
and fails. Later, the volumes can still be deleted by resetting the
state and retrying, but the user experience is cumbersome.
Upstream has fixed the issue in Caracal by refactoring the delete method
with significant behavioural changes (see comment #2), and has
backported the refactor to Antelope. Also the refactor code applies to
Yoga, it is preferred to implement a simpler fix to address this
specific problem in Yoga. The simpler fix is a retry decorator which
will force the delete method to re-run, picking up the updated reference
of the parent being deleted and therefore succeeding deleting the
childs.
[Test case]
1) Deploy Cinder with Ceph
2) Create a parent volume
openstack volume create --size 1 v1
3) Create the child volumes
for i in {1..9}; do openstack volume create d$i --source v1 --size
1;done
4) Wait for all volumes to be created and available
5) Delete all the volumes
- openstack volume delete $(openstack volume list --format value -c ID |
- sort | xargs)
+ for item in $(openstack volume list --format value -c ID | sort |
+ xargs); do openstack volume delete $item & done
6) Check for volumes stuck in error_deleting, if None, repeat steps 2-5
7) Confirm error message rbd.ImageNotFound in the logs
8) Install fixed package
- 9) Repeat steps 2-5, confirm new error message rbd.ImageNotFound in the
- logs but no volumes stuck in error_deleting
+ 9) Repeat steps 2-5, confirm no volumes stuck in error_deleting and the
+ following messages in the log:
+ "no longer exists in backend"
+
+ "Retrying
+
cinder.volume.drivers.rbd.RBDDriver.delete_volume.<locals>._delete_volume_with_retry
+ ... as it raised ImageNotFound: [errno 2] RBD image not found (error
+ opening image ... at snapshot None)"
+
+ If messages are not in the logs after the new delete command, then retry
+ steps 2-5 until messages appear while still not having any volumes stuck
+ in error_deleting (in other words, all volume deleted successfully).
[Regression Potential]
For Bobcat and Antelope, there is reasonable regression potential
because of the complexity of refactor [1] (see comment #2), however,
discussions on previous upstream meetings and upstream CI runs of
Caracal, Bobcat and Antelope backports which test the refactor provide
some level of reassurance. For Yoga, we consider no regression potential
with the simpler retry decorator fix.
[Other Info]
None.
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https://bugs.launchpad.net/bugs/2083061
Title:
[SRU] error deleting cloned volumes and parent at the same time when
using ceph
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