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From: "Ludovic Courtès" <ludo@gnu.org>
To: John Soo <jsoo1@asu.edu>
Cc: guix-devel@gnu.org
Subject: Re: RFC: subcommand to pause/resume builds
Date: Tue, 03 Nov 2020 14:53:07 +0100	[thread overview]
Message-ID: <87zh3yczss.fsf@gnu.org> (raw)
In-Reply-To: <87r1pbzixl.fsf@asu.edu> (John Soo's message of "Mon, 02 Nov 2020 10:56:38 -0800")

Hi,

John Soo <jsoo1@asu.edu> skribis:

> I was looking to pause a long build today and asked on IRC how to
> accomplish pause/resume.  It seems this is possible already with the
> following:
>
> kill --signal SIGSTOP|SIGCONT {pids-of-build-process-tree}
>
> There is already a command to list the processes associated to guix
> commands: guix processes.  Perhaps pause/resume can be a subcommand or
> set of flags to guix processes. The following is the first thing that
> comes to mind:
>
> guix processes --pause package-name ... --resume package-name ...
>
> What do you think?

First, note that the daemon is unaware of “packages”, it only knows
about “derivations”.

Second, ‘guix processes’ is nice but it uses low-level heuristics to
determine what daemon sessions are open, what their clients are, and
what they’re building; it resorts to heuristics because the daemon as it
stands doesn’t have a way to communicate its current state.  It works
well in practice, but still I wouldn’t go too far building around it.

Last, you’d need to send SIGTSTP to the whole process group of the
build, like so (I think, haven’t tried):

  sudo kill -TSTP -123

where 123 is the “SessionPID” shown by ‘guix processes’.  However, doing
so may affect build results: processes in the build environment might
handle SIGTSTP specially, which can have side effects.  It’s an
observable action.

Conclusion: I don’t think we can implement this reliably.

HTH!

Ludo’.


  reply	other threads:[~2020-11-03 13:53 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-02 18:56 RFC: subcommand to pause/resume builds John Soo
2020-11-03 13:53 ` Ludovic Courtès [this message]
2020-11-03 14:41   ` John Soo
2020-11-03 16:32   ` Tobias Geerinckx-Rice
2020-11-03 17:12     ` John Soo
2020-11-06  8:56       ` Ludovic Courtès
2020-11-03 17:19     ` Tobias Geerinckx-Rice
2020-11-03 18:27       ` John Soo
2020-11-03 20:01       ` John Soo
2020-11-06  8:58         ` Ludovic Courtès
2020-11-06 23:00           ` John Soo
2020-11-04 10:28   ` Bengt Richter
2020-11-06 21:11   ` Mark H Weaver
2020-11-08 16:30     ` Ludovic Courtès
  -- strict thread matches above, loose matches on Subject: below --
2020-11-05  4:37 John Soo

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