From: Ryan Sundberg <ryan@arctype.co>
To: mirai <mirai@makinata.eu>
Cc: guix-devel@gnu.org
Subject: Re: Expanding service procedure to accept additional arguments
Date: Thu, 5 Jan 2023 12:00:09 -0800 (PST) [thread overview]
Message-ID: <06384d87-f628-4b78-af7a-1ba199b98e85@arctype.co> (raw)
In-Reply-To: <eed5454c-9ac4-a5a6-4a4d-a6d8b633afb1@makinata.eu>
Hi Bruno,
I have written some useful macros for transforming services as you describe here. You may find them useful:
https://lab.arctype.co/poseidon/poseidon-os/-/blob/master/poseidon/services/base.scm
Sincerely,
Ryan Sundberg
Dec 28, 2022 8:48:15 AM mirai <mirai@makinata.eu>:
> It is occasionally desired to have a service depend on additional shepherd services
> than the defaults listed in their definition.
>
> Examples where this can be seen is the shepherd-requirement field provided by
> nginx-configuration and opensmtpd-configuration, but these fields are record-type
> specific and not available for the other service types (unless patched in).
>
> An alternative to patching the original record-type is to define a custom service-type
> record-type and inheriting it which is somewhat clunky for what amounts to a setup-specific
> single line change:
>
> --8<---------------cut here---------------start------------->8---
> (shepherd-service
> ...
> - (requirement `(...))
> + (requirement `(... ,@shepherd-requirement))
> --8<---------------cut here---------------end--------------->8---
>
> Another type of extensibility that should be considered is the capability to add extra
> service-extensions to existing service-type records.
> These can be useful for setup-specific (i.e. not applicable in general to be included with Guix) scenarios,
> for example, to add an extra activation-service-type extension or have a special-files-service-type
> extension that the service-type usually does not have.
>
> The current approach that I'm aware of to achieve something similar is through
> simple-service, drawbacks being extra boilerplate code and a "disjoint" service
> whose connection to the "parent service" is not immediately apparent.
>
> --8<---------------cut here---------------start------------->8---
> ;; Ideally this should go in radicale-service-type
> (simple-service 'chmod-radicale shepherd-root-service-type
> (list (shepherd-service (requirement '(user-homes))
> (provision '(radicale-home))
> (documentation "chmod g+rwx to user 'radicale' home.")
> (one-shot? #t)
> (start #~(lambda _
> (chmod (passwd:dir (getpw "radicale")) #o770)
> #t)))))
> --8<---------------cut here---------------end--------------->8---
>
>
> Instead, what if the service procedure could be changed to accept optional keyword arguments?
> Then one could express the extensions and dependencies as:
>
> --8<---------------cut here---------------start------------->8---
> (services
> (service foo-service-type
> #:requirements '(networking nscd smtpd)
> #:extensions (list (service-extension bar-service-type (lambda _ ...))
> (service-extension activation-service-type (lambda _ ...))))
> --8<---------------cut here---------------end--------------->8---
>
> Thoughts?
>
>
> Regards,
> Bruno
prev parent reply other threads:[~2023-01-05 20:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-28 16:46 Expanding service procedure to accept additional arguments mirai
2023-01-05 20:00 ` Ryan Sundberg [this message]
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