This came up while trying a simple "juju deploy mysql" (and I'm aware of https://discourse.jujucharms.com/t/whats-up-with-mysql/149/6 yes).
The mysql charm in the store currently declares its series support like this:
series:
- zesty
- xenial
- trusty
I was told the "algorithm" of picking a series, when an unqualified deploy command such as "juju deploy <name>" is received, is:
The final charm/machine series is determined using an order of precedence (most
preferred to least):
- the '--series' command option
- the series stated in the charm URL
- for a bundle, the series stated in each charm URL (in the bundle file)
- for a bundle, the series given at the top level (in the bundle file)
- the 'default-series' model key
- the top-most series specified in the charm's metadata file
(this sets the charm's 'preferred series' in the Charm Store)
May I suggest the last item be augmented with "unless that series is EOL, then the next one is tried". If none are found to be valid (all series are EOL), then juju could fail and ask the user to qualify the series, or issue a warning and pick the top-most one as originally planned, or something else.
The way it is now, "juju deploy mysql" is failing for a silly reason, when it could have picked up "xenial" as a good alternative, which is even an LTS. Furthermore, the mysql deploy failure takes a while to show up, because the charm keeps retrying apt commands against an EOL release, and the user will have to dig into juju logs to find a puzzling "404" error, and figure out ubuntu release and EOL schedules.
Thanks for filing this. I can understand the request but I feel like honestly the root here is that the charm failed to be maintained and we should have been more proactive in pulling this down vs trying to sugar coat the series to keep it limping along. That's on us for not pushing to get it pulled sooner.
I'd prefer not to put extra complexity into the process in order to cover that up. I'm marking this as won't fix but I'm happy to get feedback that I'm not thinking fairly about the proposal.