How should we change default config values in charms?

[Stuart Bishop]

On 13 August 2015 at 22:02, Jorge O. Castro <jorge at ubuntu.com> wrote:
> Hi everyone,
>
> See: https://bugs.launchpad.net/bugs/1373862
>
> This morning Marco proposed that we change the default dataset-size
> from "80%" of the memory to "128M".
>
> Ryan thinks that before we make a default change like this that we
> should discuss the implications, for example, if you have an existing
> Juju MySQL deployment, and say you want to replicate that in another
> environment, the default change is an unexpected surprise to the user.
>
> I am of the opinion that MySQL is one of the first services people
> play with when trying Juju and that the charm not working ootb with
> the local provider is a big papercut we'd like to fix.

I've discussed similar things with regard to the PostgreSQL charm and
autotuning, with the decision being that charm defaults should be set
so things 'just work' in a development environment. The rationales
were that development and testing installs are done orders of
magnitude more often than production installs, and production installs
you are almost never going to use the defaults and want to tune things
anyway.

(The PG charm rewrite is currently straddling that line, by default
auto tuning shared_buffers to 25% of RAM capped at 8GB, which will
still work under lxc even if its a little overzealous while still
being 'best practice' default tuning).

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