Re: Proposal: auto-instantiate services with a default value

[Ludovic Courtès]

Ricardo Wurmus <address@hidden> skribis:

> Ludovic Courtès <address@hidden> writes:
>
>>> Also, that means that the instantiated mcron-service would automatically 
>>> get a rottlog entry even though the mcron-service-types's default job list 
>>> is empty, right ?
>>
>> Correct.
>>
>>> In that case it would be nice to be able to (optionally) override this 
>>> mcron-service by a custom mcron-service in /etc/config.scm but retain the 
>>> modified configuration with the implicit job in it.  Is that possible?
>>
>> Sure, the current way to do things (which is to explicitly list rottlog
>> *and* mcron) would remain valid, and you could pass your own mcron
>> config this way.
>
> If a user already had an mcron service with a custom configuration,
> it would still be extended as needed by adding the rottlog-service — or
> am I mistaken?

Yes.  Basically an existing currently-working configuration will still
work exactly the same.

The novelty is that one would now be able to omit services that are
indirectly needed.

> I think auto-instantiation is great when it all shows up with “guix
> system extension-graph” and users can thus figure out why certain
> services were instantiated unexpectedly.

Yes.  Speaking of which, it’d be great to have an interactive view of
service folding (d3.js?)…

Ludo’.