Re: Creating Docker containers in Scheme

[Roel Janssen <roel@gnu.org>]

Ludovic Courtès writes:

> Hi,
>
> Roel Janssen <roel@gnu.org> skribis:
>
>> I'd like to create a Docker container from Scheme.  Looking at
>> guix/scripts/pack.scm, I believe something like this should be possible:
>>
>>   (docker-image "my-container"
>>     (profile-derivation
>>       (packages->manifest (list hello coreutils))))
>
> Move precisely:
>
>   (mlet %store-monad ((profile (profile-derivation …)))
>     (docker-image "my-container" profile))
>

Oh, of course! :)

Unfortunately, I cannot seem to get it to work.
Here's what I do (mind the GWL process- stuff):

--8<---------------cut here---------------start------------->8---
(define* (process->docker-derivation proc #:key (guile (default-guile)))
  "Return a Docker container that can run the PROCEDURE described in PROC, with
PROCEDURE's imported modules in its search path."
  (let ((name (process-full-name proc))
        (exp (process-procedure proc))
        (out (process-output-path proc))
        (packages (process-package-inputs proc)))
    (let ((out-str (if out (format #f "(setenv \"out\" ~s)" out) "")))
      (mlet %store-monad ((set-load-path
                           (load-path-expression (gexp-modules exp)))
                          (container (docker-image
                                      (string-append (process-full-name proc)
                                                      "-docker")
                                      (profile-derivation
                                       (packages->manifest packages)))))
        (gexp->derivation
         name
         (gexp
          (call-with-output-file (ungexp output)
            (lambda (port)
              (format port "# Docker image: ~a~%" (ungexp container)))))
         #:graft? #f)))))
--8<---------------cut here---------------end--------------->8---

And the error I get is:
  wrong-type-arg: string-prefix?

Is there anything obviously wrong here?

>> Is this something we could add to the the public interface of a module?
>
> Sure.  For now the easiest solution would be to export ‘docker-image’
> from (guix scripts pack).
>
> Longer-term, we could rename (guix docker) to (guix build docker) and
> move ‘docker-image’ to a new (guix docker) module, but perhaps we’d also
> need a (guix pack) modules containing tools that are shared between the
> docker and tarball backends of ‘guix pack’.
>
> WDYT?

It'd be nice to keep the (guix scripts ...) small, and only do
command-line handling.  So I think a (guix build docker), and a (guix
pack) module would be good.

>
> Ludo’.

Thanks for your time!

Kind regards,
Roel Janssen