improve surfacing disable_modules / site_modules conflicts

[Junien F]

Hi,

If an apache-website relation requires a module that's in the juju config "disable_modules", the charm doesn't really surface that.

For example, if you relate telegraf:apache to apache2:apache-website, telegraf will try to setup a vhost requiring the "status" module. However, this module is by default in the "disable_modules" juju config, and so the vhost is not enabled and it's not super clear why.

We should improve this, probably by setting the status to "blocked" with the appropriate message - and also write something in the logs.

Thanks

[Haw Loeung (hloeung)]

Perhaps the telegraf charm should also check if the 'status' module is enabled and surface this if not.

[Eric Chen (eric-chen)]

Soon or later, the monitoring system will migrate to COS. Telegraf will be replaced by grafana-agent.
(https://charmhub.io/topics/canonical-observability-stack)
This feature won't be implemented.