Hi,

Ludovic Courtès <ludo@gnu.org> skribis:

>   1. In the best case, shepherd (as of 0.9.1) is stuck while ‘system*’
>      is in ‘waitpid’ waiting for child process completion (“stuck” as
>      in: doesn’t do anything, not even answering ‘herd’ requests or
>      inetd connections.)
>
>   2. I don’t think that can happen with ‘system*’ (because it’s in C),
>      but generally speaking, there’s a possibility that shepherd’s event
>      loop will handle child process termination before some other
>      user-made ‘waitpid’ call does.
>
> Anyway, that’s a bad situation.
>
> So I can think of several ways to address it:
>
>   1. Change the nginx service ‘stop’ method to just
>      (make-kill-destructor), which should work just as well as invoking
>      “nginx -s stop”.
>
>   2. Have Shepherd provide a replacement for ‘system*’.

These fresh Shepherd commits install a non-blocking ‘system*’ replacement:

  975b0aa service: Provide a non-blocking replacement of 'system*'.
  039c7a8 service: Spawn a fiber responsible for process monitoring.

We’ll have to do more testing and probably go for a 0.9.3 release soon.

Protip: you can test the latest shepherd with:

--8<---------------cut here---------------start------------->8---
(operating-system
  ;; …
  (essential-services
   (modify-services (operating-system-default-essential-services
                     this-operating-system)
     (shepherd-root-service-type
      config =>
      (shepherd-configuration
       (shepherd (package
                   (inherit shepherd-0.9)
                   (version "0.9.3pre")
                   (source (git-checkout
                            (url "https://git.savannah.gnu.org/git/shepherd.git")))
                   (native-inputs
                    (modify-inputs (package-native-inputs shepherd-0.9)
                      (append autoconf automake help2man texinfo gnu-gettext))))))))))
--8<---------------cut here---------------end--------------->8---

Full example attached.

Ludo’.