Failed to upgrade mysql-router from latest/stable to 8.0/stable

[Chi Wai CHAN]

When deploy a simple keystone charm with mysql-router charm and mysql-innodb-database charm, mysql-router is blocked by: Failed to connect to database due to '(2003, "Can't connect to MySQL server on '127.0.0.1:3306' (111)")'. This is a known bug from #1973177, and it has a fix on 8.0/stable. Therefore, I have attempted to upgrade the mysql-router charm to 8.0/stable, but the upgrade was not successful and it failed with the same error status: 2003.

Also see the attachment for the traceback of this error and how the model is deployed.

Furthermore, the problem can be solved by running:

- `juju run-action keystone-mysql-router pause`

- (`juju resolved keystone-mysql-router/0` might be required to put it into maintainance state)

- `juju run-action keystone-mysql-router resume`

[Felipe Reyes (freyes)]

The issue here is that during the upgrade charm operation we don't restart the mysql-router service, the files are correctly rendered.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/charm-mysql-router/+/848748

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Felipe Reyes <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/charm-mysql-router/+/848748

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-mysql-router/+/848673
Committed: https://opendev.org/openstack/charm-mysql-router/commit/6df798a939c9f5e167a73f6e8c145c6ec631ac6c
Submitter: "Zuul (22348)"
Branch: master

commit 6df798a939c9f5e167a73f6e8c145c6ec631ac6c
Author: Rodrigo Barbieri <email address hidden>
Date: Mon Jul 4 17:22:02 2022 -0300

    Fix restarts during upgrade-charm hook

    Upgrade-charm code needs to make various adjustments to
    the config files and restart the mysql-router service,
    but the code is currently running config-changed and
    getting stuck in a restart loop before upgrade-charm
    is able to run to make the config adjustments and
    invoke a successful restart.

    This change adds a condition to skip the execution of
    config_changed function when upgrade-charm hook runs,
    so upgrade_charm code takes care of the adjustments.

    Also, now upgrade-charm hook is guaranteed to restart the
    mysql-router service whenever any change to the config
    file is made as part of its execution, whereas before
    it wasn't doing so when making the adjustments of the
    custom upgrade_charm function, resulting in the possibility
    of no restarts after a charm upgrade.

    This change includes the now-abandoned change:
    https://review.opendev.org/848748

    Co-Authored-By: Felipe Reyes <email address hidden>

    Closes-bug: #1980693
    Closes-bug: #1979263
    Related-bug: #1927981
    Change-Id: If9d71bdb839c9c0ee3f4b33e4d44a5c93bdd13de

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/jammy
Review: https://review.opendev.org/c/openstack/charm-mysql-router/+/851761

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-mysql-router/+/851761
Committed: https://opendev.org/openstack/charm-mysql-router/commit/cfe6b2e3c0081fdc9c3aafec26a942e722de34a9
Submitter: "Zuul (22348)"
Branch: stable/jammy

commit cfe6b2e3c0081fdc9c3aafec26a942e722de34a9
Author: Rodrigo Barbieri <email address hidden>
Date: Mon Jul 4 17:22:02 2022 -0300

    Fix restarts during upgrade-charm hook

    Upgrade-charm code needs to make various adjustments to
    the config files and restart the mysql-router service,
    but the code is currently running config-changed and
    getting stuck in a restart loop before upgrade-charm
    is able to run to make the config adjustments and
    invoke a successful restart.

    This change adds a condition to skip the execution of
    config_changed function when upgrade-charm hook runs,
    so upgrade_charm code takes care of the adjustments.

    Also, now upgrade-charm hook is guaranteed to restart the
    mysql-router service whenever any change to the config
    file is made as part of its execution, whereas before
    it wasn't doing so when making the adjustments of the
    custom upgrade_charm function, resulting in the possibility
    of no restarts after a charm upgrade.

    This change includes the now-abandoned change:
    https://review.opendev.org/848748

    Co-Authored-By: Felipe Reyes <email address hidden>

    Closes-bug: #1980693
    Closes-bug: #1979263
    Related-bug: #1927981
    Change-Id: If9d71bdb839c9c0ee3f4b33e4d44a5c93bdd13de
    (cherry picked from commit 6df798a939c9f5e167a73f6e8c145c6ec631ac6c)