Deprecating charm config options: postgresql case

Stuart Bishop stuart.bishop at canonical.com
Thu Jan 14 23:03:22 UTC 2016


On 15 January 2016 at 02:00, Andreas Hasenack <andreas at canonical.com> wrote:

>   max_connections:
>     default: 100
>     type: int
>     description: >
>         DEPRECATED. Use extra_pg_conf.
>         Maximum number of connections to allow to the PG database
>
> The option still exists and can be set, but does nothing. The service will
> get whatever is set in the new extra_pg_conf option, which happens to be
> 100.

That would be a bug. It is supposed to still work, with warnings in
your logs that you are using deprecated options.


> Other deprecated options have a more explicit warning:
>
>   performance_tuning:
>     default: "Mixed"
>     type: string
>     description: >
>         DEPRECATED AND IGNORED. The pgtune project has been abandoned
>         and the packages dropped from Debian and Ubuntu. The charm
>         still performs some basic tuning, which users can tweak using
>         extra_pg_config.
>
> In this specific postgresql case, looks like all (I just tested two, btw)
> deprecated options should have been marked with the extra "... AND IGNORED"
> text. But then again, is it worth it to silently accept them and do nothing,
> thereby introducing subtle run-time failures?

Just dropping options risks breaking lots of mojo specs, all at the
same time. The plan is to log warnings, escalate to irritating
workload status messages later, and eventually drop them. All the
options that matter are supposed to still be functional, and the few
being ignored done so after careful consideration of the impact.

I think there are also issues to deal with for upgrade-charm, although
Juju might have changed its behaviour since I last looked (are service
settings that no longer exist now silently dropped, or do they block
the upgrade?)

-- 
Stuart Bishop <stuart.bishop at canonical.com>



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