Re: Defining shepherd user services -- feedback desired

[Ludovic Courtès]

Hey Alex,

Alex ter Weele <address@hidden> skribis:

> Attached is a manifest file which allows a user to write a
> shepherd-service like the following:
>
> (define redshift-service
>   (shepherd-service
>    (provision '(redshift))
>    (modules `((gnu packages xdisorg)
>               ,@%default-modules))
>    (start #~(make-forkexec-constructor
>              (list (string-append #$redshift "/bin/redshift")
>                    "-l" "50:4")))))
>
> And transform it into a package:
>
> (services->package (list redshift-service))
>
> This allows it to be included in a user's profile. This unites the
> definition of a service with its dependencies (redshift, in the example
> above). A user would not have to install a package just to use it as a
> service, nor would they have to hand-write a Shepherd configuration
> file.

Indeed, that’s a neat hack!  And it ties software and service
deployment, which is great.

> ;; the next two are copied from (gnu services shepherd) because:
>
> ;; * (gnu services shepherd)'s version of shepherd-configuration-file
> ;; is for the pid1 shepherd and has some stuff like fallback-to-REPL
> ;; that is not necessary for user services.
>
> ;; * (gnu services shepherd) doesn't export
> ;; shepherd-configuration-file.

That we can fix.  :-)  Would it be enough for you?

I don’t think the first item is a showstopper, is it?

> (define (services->package services)
>   "Yield a package for SERVICES by making them into a shepherd
> configuration file via scheme-file."

This makes me think that perhaps we should generalize profile, and allow
non-package objects in there—it doesn’t feel right to define a <package>
for something that’s conceptually not a package at all.

But then that leads to issues, like what should ‘guix package -u’ do?
How should ~/.guix-profile/manifest represent these non-package things?
Should we add ‘guix package --install-service’ or similar?  (Well, that
may be overboard…)

It would be nice to think about whether/how we could make this part of
Guix proper.

Thanks!

Ludo’.