Comment 19 for bug 2008248

Hi,

Just supplying this thread with workarounds I did during production cloud upgrade. I faced this issue with the following charms:
* octavia-diskimage-retrofit which is related to glance-simplestream-sync unit
* lldpd which is related to nova-compute
* grafana-agent which is related to every primary charm in OpenStack model
* keystone-saml-mellon which is related to keystone

1. Before series upgrades all charms were refreshed to their latest/stable or yoga/latest channels while machines and LXDs were still on Focal. lldpd I refreshed to `latest/candidate` because it is shown in charmhub as the one supported by Jammy.
2. During the series upgrade I had to run "juju upgrade-series <> prepare jammy --force -y" for all my principal charms
3. After series were upgraded, some charms were broken during "juju upgrade-series <> complete". The following ones were in error state and I helped `upgrade-sereis` to complete with `juju resolved --no-retry <>`: grafana-agent, octavia-diskimage-retrofit, keystone-saml-mellon. lldpd figured out by itself
4. After all series upgrades were done, I fixed the charms:
  * octavia-diskimage-retrofit I just redeployed, because it doesn't produce any downtime. Just removed and added relation with principal
  * grafana-agent I resolved to revision 28 (!) and it just worked. I tried to switch between channels, but nothing helped, `latest/stable` produce missing `cryptography` dependency error, `latest/edge` wants Juju 3. Just by blindly guessing I found this revision 28 which works.
  * keystone-saml-mellon units still show "Ready for do-release-upgrade and reboot. Set complete when finished." to me. But that doesn't seem to affect charm behavior, it reacts to config changes. I don't want to redeploy it not to cause any Keystone auth downtimes. I tried to run `hooks/post-series-upgrade` hook manually, tried to use `status-set`, but it still goes to "Blocked"; nothing obvious in juju MongoDB.

Hope that will help somebody to get from Focal to Jammy and to Juju 3 eventually.