edk@beaver-labs.com schreef op zo 11-04-2021 om 21:31 [+0200]:
> Dear fellow Guixers,

> [...]
> But, when I try to run it with shepherd, it fails because it can't find
> flask (a dependency of the software, which I've put as a
> propagated-input, and is indeed installed in the container).

Propagated inputs can be inconvenient at times.  I would advise
looking where requisomatic is referring to flask, and replacing
flask --> (string-append (assoc-ref inputs "flask") "/bin/flask")
using substitute*.

> But, when I try to run it with shepherd, it fails because it can't find
> flask (a dependency of the software, which I've put as a
> propagated-input, and is indeed installed in the container).
> [...]

Some advice (warning: I'm not familiar with gunicorn or requisomatic at all).

> 
> -----extract from my operating-system declaration file-------
> (define requisomatic-shepherd-service
>   ([...] (shepherd-service
>             [...]
            (documentation "Run the requisomatic server")
>             (start #~((make-forkexec-constructor
>                     ;;   (append
>                     ;;    (if db-file
>                     ;;      `("env"
>                     ;;        ,(string-append "REQUISOMATIC_DB_FILE=" db-file))
>                     ;;      '())
>                                         '("gunicorn" "requisomatic:app")

Normally, services refer by absolute path to the binary to run, and not rely
on the PATH (the latter would require polluting the system profile).
Idiomatically, one would write

  '(#$(file-append gunicorn "/bin/gunicorn")
    #$(file-append requisomatic) "/wherever/the/binary/is")

>                        #:directory (string-append #$requisomatic "/bin/requisomatic/")

Why are you changing the working directory to
(string-append #$requisomatic "/bin/requisomatic/"), and why is "/bin/requisomatic" a
directory and not an executable?  Is that a gunicorn thing?

> Why is the PYTHONPATH (and the other env vars, for that matter) not
> propagated from the package to the shepherd service by default ?

How is the shepherd service supposed to automagically know which packages
to include in the environment variables?

> And how can I make it so ?

Use the #:environment-variables option, see e.g. bitlbee-shepherd-service
Or create a wrapper.  See e.g. wrapped-dbus-service.

> Follow up question, can shepherd services be specified to run in a
> specific profile ?

IIUC, currently shepherd services aren't run in *any* profile at all.
It would be useful to have a function manifest->environment-gexp though.

> So that I can have two services with incompatible
> dependencies running at the same time in the same operating-system ?
Yes, it with "dependencies" you mean packages, and not other services.

Greetings,
Maxime.