pausing hacluster no longer needed during series upgrades

[Andrea Ieri]

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-----------------------------------
Release: 0.0.1.dev753 on 2023-08-16 18:30:42
SHA: 74d0eea30bb8e75a908a733b729ada99859f213f
Source: https://opendev.org/openstack/charm-guide/src/doc/source/admin/upgrades/series-openstack.rst
URL: https://docs.openstack.org/charm-guide/latest/admin/upgrades/series-openstack.html

Commit https://github.com/openstack/charm-hacluster/commit/d3512ef320e298142bfe9a3c3e96f342ab9a4cc6 introduced a mechanism for stopping HA services when undergoing a series upgrade (since pacemaker packages cannot be guaranteed to be interoperable across Ubuntu series); as a consequence, the guidance to pause the hacluster charm before starting a series upgrade is no longer necessary.

Specifically, I think the following sentence should be dropped from https://docs.openstack.org/charm-guide/latest/admin/upgrades/series-openstack.html#generalised-openstack-series-upgrade:

> If hacluster is used, pause the hacluster units not associated with the principal leader machine.

Additionally, I think a note should be added to warn users that HA clusters will be inoperable throughout the upgrade (of a given application); this is a behavior change as it used to be possible to keep the cluster alive by carefully pausing only one unit at a time.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/charm-guide/+/893436

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-guide/+/893436
Committed: https://opendev.org/openstack/charm-guide/commit/9967a8f91b22a06cf81c4c97ca2617941149ac8e
Submitter: "Zuul (22348)"
Branch: master

commit 9967a8f91b22a06cf81c4c97ca2617941149ac8e
Author: Peter Matulis <email address hidden>
Date: Thu Aug 31 15:35:59 2023 -0400

    Fix described hacluster behaviour for series upgrades

    Correct documented steps that suggest that pausing hacluster
    units during a series upgrade makes a difference in terms
    of preventing downtime. This has not been the case since
    early 2020 (commit-wise).

    Closes-Bug: #2033546
    Relates-To: Id9167534e8933312c561a6acba40399bca437706
    Change-Id: I6bbfc14a445a972eb48aab8894d633f1aa5a5e6f
    Signed-off-by: Peter Matulis <email address hidden>