GNU bug report logs - #48521
opendht-service-type hangs Shepherd at boot

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
Subject: bug#48521: closed (Re: bug#48521: opendht-service-type hangs
 Shepherd at boot)
Date: Thu, 20 May 2021 02:53:02 +0000

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Your bug report

#48521: opendht-service-type hangs Shepherd at boot

which was filed against the guix package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 48521 <at> debbugs.gnu.org.

-- 
48521: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=48521
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: 48521-done <at> debbugs.gnu.org
Subject: Re: bug#48521: opendht-service-type hangs Shepherd at boot
Date: Wed, 19 May 2021 22:52:06 -0400

Hello,

Maxim Cournoyer <maxim.cournoyer <at> gmail.com> writes:

> Hello,
>
> I just noticed about this problem following a reboot.  I can also
> reproduce it in 'guix system vm', simply adding the opendht-service-type
> to my operating-system declaration.
>
> The boot proceeds until 'error in finalization thread: Success' then
> hangs indefinitely.
>
> What is troubling for me is that the service is rather straightforwardly
> defined.  It uses the make-forkexec-constructor/container like so:
>
> (define (opendht-shepherd-service config)
>   "Return a <shepherd-service> running OpenDHT."
>   (shepherd-service
>    (documentation "Run an OpenDHT node.")
>    (provision '(opendht dhtnode dhtproxy))
>    (requirement '(user-processes syslogd))
>    (start #~(make-forkexec-constructor/container
>              (list #$@(opendht-configuration->command-line-arguments config))
>              #:mappings (list (file-system-mapping
>                                (source "/dev/log") ;for syslog
>                                (target source)))
>              #:user "opendht"))
>    (stop #~(make-kill-destructor))))
>
> I'm not sure how using such basic building blocks could lead to a hang
> in Shepherd ?

It seems Shepherd can't cope with a failing start procedure/script when
a variable was not bound.  To diagnose the problem, the best way ended
up being to extract the code of the constructor in a separate script to
run it separately.  This made the error quickly apparent: "Unbound
variable: file-system-mapping".

We should try to handle this class of errors in Shepherd and report a
useful message and *not* crash Shepherd or otherwise hang.

Pushed with commit a09cdf1f9d.

Closing.

Maxim

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From: Maxim Cournoyer <maxim.cournoyer <at> gmail.com>
To: bug-guix <bug-guix <at> gnu.org>
Subject: opendht-service-type hangs Shepherd at boot
Date: Wed, 19 May 2021 07:59:19 -0400

Hello,

I just noticed about this problem following a reboot.  I can also
reproduce it in 'guix system vm', simply adding the opendht-service-type
to my operating-system declaration.

The boot proceeds until 'error in finalization thread: Success' then
hangs indefinitely.

What is troubling for me is that the service is rather straightforwardly
defined.  It uses the make-forkexec-constructor/container like so:

--8<---------------cut here---------------start------------->8---
(define (opendht-shepherd-service config)
  "Return a <shepherd-service> running OpenDHT."
  (shepherd-service
   (documentation "Run an OpenDHT node.")
   (provision '(opendht dhtnode dhtproxy))
   (requirement '(user-processes syslogd))
   (start #~(make-forkexec-constructor/container
             (list #$@(opendht-configuration->command-line-arguments config))
             #:mappings (list (file-system-mapping
                               (source "/dev/log") ;for syslog
                               (target source)))
             #:user "opendht"))
   (stop #~(make-kill-destructor))))
--8<---------------cut here---------------end--------------->8---

I'm not sure how using such basic building blocks could lead to a hang
in Shepherd ?

Thanks,

Maxim

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