Re: Watchdog wrapper for s6

From: Alex Kiernan <>
Date: Sun, 21 Nov 2021 15:25:45 +0000

On Sat, Nov 20, 2021 at 9:57 PM Laurent Bercot <> wrote:
> >I have a problem process that's getting stuck somewhere in its network
> >code (clearly the right answer is to find/fix the problem, but it's
> >infrequent and we're up against time constraints...)
> >
> >I'm looking at just adding a wrapper around it which does something
> >along the lines of the existing s6 notification - have the supervised
> >process write a regular character to an inherited fd, if it ever stops
> >then the wrapper kills everyone and exits allowing the supervision to
> >restart it.
> What you want is process monitoring. s6 doesn't do that, because
> the monitoring needs are very process-specific and it's impossible to
> predict all the functionality that every daemon under the sun could
> want to use.

Indeed, wasn't sure if I was missing something!

> Here, you need a heartbeat. You can implement the heartbeat monitor
> as a separate service, which it is: it's a service that reads the
> heartbeat from your daemon and sends it an s6-svc -r command when
> it fails to receive the heartbeat from a period of time.
> If you don't need anything more than that, you can probably write
> the heartbeat monitor in shell (or even in execline!) It's a call
> to mkfifo then a read loop. :)

Thanks for the steer on the pattern.

Alex Kiernan
Received on Sun Nov 21 2021 - 16:25:45 CET

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