bug#53225: shepherd freezes if wireguard is started with dns config enabled

[Nathan Dehnel <ncdehnel@gmail.com>]

Just tested and Shepherd 0.9 does not fix this issue.

On Mon, Jan 17, 2022 at 7:48 AM Ludovic Courtès <ludo@gnu.org> wrote:
>
> Hi,
>
> Nathan Dehnel <ncdehnel@gmail.com> skribis:
>
> >>What do you mean by “freezing”?  Does ‘herd status’ and similar commands
> > block forever?
> > Yes
> >
> >>Requests in the Shepherd are currently handled sequentially.  So if you
> > issue several ‘herd restart’ commands, they’ll be processed one at a
> > time.  This is usually okay because ‘start’ commands are expected to be
> > quick (just wait for the daemon to write its PID file or similar).
> > What is the nature of this serialization? Does wireguard need to
> > finish before resolvconf can start? Because that's probably the issue.
>
> One command sent to shepherd by ‘herd …’ must have completed before the
> next one is processed.
>
> You can experience it like this:
>
>   sudo herd eval root '(sleep 3)' & echo status && sudo herd status
>
> Here the first ‘herd’ command has shepherd block for 3 seconds, so the
> second ‘herd’ command won’t print anything until 3 seconds have passed.
>
> HTH,
> Ludo’.