[posix] cinder schedules incremental backups on the wrong node

[Andrew Bogott]

I'm running 17.2 with the posix backend and two cinder-backup nodes.

When I run an incremental backup, the increment has a 50/50 chance of working: if it's scheduled on the same node that got the original full backup then it works, and if it gets scheduled on the other node with no full backup it fails:

2021-11-30 20:50:42.159 11905 ERROR oslo_messaging.rpc.server FileNotFoundError: [Errno 2] No such file or directory: '/srv/cinder-backups/28/77/2877b51f-6b0e-47ab-9582-bd5d12f6b7a3/volume_74bf4553-c92e-4fd5-88ef-33fb789ab07a_20211130204954_backup_2877b51f-6b0e-47ab-9582-bd5d12f6b7a3_sha256file

That file isn't found because it's on the other node, not this one.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/cinder/+/861566

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/cinder/+/861566
Committed: https://opendev.org/openstack/cinder/commit/73c0d73aba1855edb774d69ae940a1b53dc975e0
Submitter: "Zuul (22348)"
Branch: master

commit 73c0d73aba1855edb774d69ae940a1b53dc975e0
Author: Andrew Bogott <email address hidden>
Date: Sun Oct 16 22:37:36 2022 -0500

    cinder-backup: use the same backup backend host for incremental backups

    Incremental backups only work if there's a previous backup to base
    it on. With the posix driver, this means there needs to be a previous
    backup on the same host where the incremental backup is created.

    This patch ensures that an incremental backup is scheduled on the
    host that that contains the base backup being used for the increment.
    Previously we were relying on luck for this and much of the time an
    incremental backup would fail due for want of a base backup.

    Closes-bug: 1952805
    Change-Id: Id239b4150b1c8e9f4bf32f2ef867fdffbe84f96d

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/cinder 22.0.0.0rc1 release candidate.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/zed
Review: https://review.opendev.org/c/openstack/cinder/+/916044

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Elod Illes <email address hidden>" on branch: stable/zed
Review: https://review.opendev.org/c/openstack/cinder/+/916044
Reason: stable/zed branch of openstack/cinder is about to be deleted. To be able to do that, all open patches need to be abandoned. Please cherry pick the patch to unmaintained/zed if you want to further work on this patch.