Comment 5 for bug 2037003

Reviewed: https://review.opendev.org/c/openstack/charm-nova-compute/+/905312
Committed: https://opendev.org/openstack/charm-nova-compute/commit/28233f9a943f9c6c67d4934cf693869c9c03b1e4
Submitter: "Zuul (22348)"
Branch: stable/2023.2

commit 28233f9a943f9c6c67d4934cf693869c9c03b1e4
Author: Rodrigo Barbieri <email address hidden>
Date: Fri Oct 6 10:24:48 2023 -0300

    [v2] Fix migration across nova-compute apps using ceph

    This change reworks previous changes [1] and [2] that had
    been respectively reverted and abandoned.

    When using the config libvirt-image-backend=rbd, VMs
    created from image have their disk data stored in ceph
    instead of the compute node itself.

    When performing live-migrations, both nodes need to
    access the same ceph credentials to access the VM's
    disk in ceph, but this is currently not possible
    if the nodes involved pertain to different
    nova-compute charm apps.

    This patch changes app name sent to ceph to
    'nova-compute-ceph-auth-c91ce26f', a unique name common to
    all nova-compute apps, allowing all nova-compute apps to
    use the same ceph auth.

    This change also ensures newly deployed nodes install
    the old credentials first on ceph-joined hook,
    and then supercedes it with the new credentials
    on ceph-changed hook, therefore also retaining
    the old credentials.

    [1] https://review.opendev.org/889642
    [2] https://review.opendev.org/896155

    Closes-bug: #2028559
    Related-bug: #2037003

    Func-Test-Pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/1183

    Change-Id: I1ae12d787a1f8e7761ca06b5a80049c1c62e9e90
    (cherry picked from commit 650f3a5d511690ec27648b30f3b24532378a33a1)