GNU bug report logs - #71144
Interactive prompt opened upon shepherd config file error

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Ludovic Courtès <ludo <at> gnu.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#71144: closed (Interactive prompt opened upon shepherd config
 file error)
Date: Sat, 25 May 2024 15:00:03 +0000

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Your message dated Sat, 25 May 2024 16:59:16 +0200
with message-id <87sey6ym2j.fsf <at> gnu.org>
and subject line Re: bug#71144: Interactive prompt opened upon shepherd config file error
has caused the debbugs.gnu.org bug report #71144,
regarding Interactive prompt opened upon shepherd config file error
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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71144: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=71144
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From: Ludovic Courtès <ludovic.courtes <at> inria.fr>
To: bug-guix <at> gnu.org
Subject: Interactive prompt opened upon shepherd config file error
Date: Thu, 23 May 2024 12:59:40 +0200

Hello,

One problem we noticed in the analysis of the boot problem of bayfront
after the recent downtime¹ is that an interactive REPL would be opened
after an unbound variable was found in the shepherd config file:

--8<---------------cut here---------------start------------->8---
[   13.098907] shepherd[1]: Service root started.
[   13.100711] shepherd[1]: Service root running with value #t.
[   13.103824] shepherd[1]: Service root has been started.
[   13.426102] shepherd[1]: ice-9/boot-9.scm:1685:16: In procedure raise-exception:
[   13.428099] shepherd[1]: Unbound variable: make-forkexec-constructor/container
[   13.429912] shepherd[1]: 
[   13.431108] shepherd[1]: Entering a new prompt.  Type `,bt' for a backtrace or `,q' to continue.
[   13.441983] shepherd[1]: GNU Guile 3.0.9
[   13.442728] shepherd[1]: Copyright (C) 1995-2023 Free Software Foundation, Inc.
[   13.443947] shepherd[1]: 
[   13.444427] shepherd[1]: Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
[   13.445679] shepherd[1]: This program is free software, and you are welcome to redistribute it
[   13.446919] shepherd[1]: under certain conditions; type `,show c' for 
[   13.447072] shepherd[1]: details.
[   13.448737] shepherd[1]: 
[   13.449239] shepherd[1]: Enter `,help' for help.
--8<---------------cut here---------------end--------------->8---

This was unhelpful because we couldn’t interact with that REPL remotely
(no IPMI).  Even when you can interact, it’s of limited use; in this
case, if you type “,q”, it tries to continue and fails:

--8<---------------cut here---------------start------------->8---
Uncaught exception in task:
In fibers.scm:
    172:8  7 (_)
In ice-9/exceptions.scm:
   406:15  6 (_)
In ice-9/boot-9.scm:
  1752:10  5 (with-exception-handler _ _ #:unwind? _ # _)
In shepherd/service.scm:
   824:39  4 (_)


this is because we’re effectively adding #f in the middle of the list
passed to ‘register-services’ (see below).

This REPL-on-error “feature” comes from Guix System, not Shepherd, in
the config file generated from (gnu services shepherd):

    ;; Arrange to spawn a REPL if something goes wrong.  This is better
    ;; than a kernel panic.
    (call-with-error-handling
      (lambda ()
        (register-services
         (parameterize ((current-warning-port
                         (%make-void-port "w")))
           (map (lambda (file)
                  (save-module-excursion
                   (lambda ()
                     (set-current-module (make-user-module))
                     (load-compiled file))))
                '#$(map scm->go files))))))

The rationale mentioned in the comment no longer holds: starting from
Shepherd 0.10.2, the config file is loaded in the background; if it’s
evaluation fails, shepherd keeps running (see
‘tests/config-failure.sh’, which tests this behavior).

I think we should change the above to log and gracefully handle failure
to load an individual service file.

Ludo’.

¹ https://lists.gnu.org/archive/html/info-guix/2024-05/msg00000.html

[Message part 3 (message/rfc822, inline)]

From: Ludovic Courtès <ludo <at> gnu.org>
To: Christopher Baines <mail <at> cbaines.net>
Cc: 71144-done <at> debbugs.gnu.org, Andreas Enge <andreas <at> enge.fr>
Subject: Re: bug#71144: Interactive prompt opened upon shepherd config file
 error
Date: Sat, 25 May 2024 16:59:16 +0200

Christopher Baines <mail <at> cbaines.net> skribis:

> That looks good to me, the "Arrange to spawn a REPL if something goes
> wrong" comment needs removing/updating, but that's the only thing I
> spotted.

Cool.  I updated the comment and pushed it as
cca25a67693bb68a1884a081b415a43fad1e8641.

Thanks!

Ludo’.

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