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From: Tanuj Bagaria <gnutanuj@gmail.com>
To: Laurent Bercot <ska-supervision@skarnet.org>
Cc: supervision@list.skarnet.org
Subject: Re: Have an external script wait for a oneshot service
Date: Thu, 5 Dec 2024 09:59:50 +0400	[thread overview]
Message-ID: <B4CB6C78-2B94-4479-8906-A18FCF11DB6A@gmail.com> (raw)
In-Reply-To: <em7af28a17-e9ab-4531-acfe-2be95ab4507e@af2df4ac.com>

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> On 5 Dec 2024, at 01:58, Laurent Bercot <ska-supervision@skarnet.org> wrote:
> 
> 
>> 
>> Although it would be nicer to have a standard way to do this
> 
> There is a standard way to block until a oneshot has completed:
> depend on that oneshot.
> 
> Duh.
> 
> The thing is, s6-rc wasn't designed to have external scripts
> interacting in this way with this engine, because if you have programs
> depending on intermediary s6-rc states, they should be managed by s6-rc
> as well. The point is to have a predictable machine state when s6-rc
> exits; if you have random other stuff doing things in parallel, that
> defeats the purpose.
> 
> And with an s6-linux-init setup, at boot time there is no other
> process than s6-rc managing your services. You have the supervision
> tree, and the stage 2 script, and that's it. And if you're going to
> spawn stuff in your rc.init that waits for oneshot X in the s6-rc db,
> then... why? Why not have said stuff as another service?
> 
> If you cannot, for whatever reason, maybe bring your services up in
> two steps?
>     s6-rc change X && stuff & s6-rc change default
> 
> And if all else fails, the generic solution would be to have a oneshot
> Y depending on X (so, that would run once X is done) that sends a
> notification to a place of your choice via a mechanism of your choice,
> you could use a fifodir and s6-ftrig-notify for this. You would still
> have to deal with the race conditions around setting up the listener etc.
> 
> The cleanest way to achieve what you want, without support in the
> service set itself, is to s6-rc change X first, then s6-rc change the
> rest of your services. That way, you avoid breaking abstraction with
> hacks of questionable aesthetic value.
> 
> --
> Laurent
> 

  reply	other threads:[~2024-12-05  6:00 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-12-04 15:28 Paul Sopka
2024-12-04 15:38 ` Charles Cazabon via supervision
2024-12-04 17:12   ` Paul Sopka
2024-12-04 21:47     ` Hoël Bézier
2024-12-04 20:00 ` Brett Neumeier via supervision
2024-12-04 20:05   ` Paul Sopka
2024-12-04 20:18     ` Brett Neumeier via supervision
2024-12-04 20:59       ` Paul Sopka
2024-12-04 21:58         ` Re[2]: " Laurent Bercot
2024-12-05  5:59           ` Tanuj Bagaria [this message]
2024-12-05  6:54           ` Paul Sopka
2024-12-05  8:05             ` Re[2]: " Laurent Bercot
2024-12-05 13:52               ` Paul Sopka
2024-12-05 19:44                 ` Re[2]: " Laurent Bercot
2024-12-05 21:10                   ` Paul Sopka
2024-12-05 21:42                     ` Brett Neumeier via supervision
2024-12-06  5:32                       ` Paul Sopka
2024-12-05 23:03                     ` Re[2]: " Laurent Bercot
2024-12-06 12:41                       ` Paul Sopka
2024-12-06 15:43                         ` Re[2]: " Laurent Bercot
2024-12-06 16:11                           ` Hoël Bézier
2024-12-06 17:14                           ` Paul Sopka
2024-12-07 23:46                           ` Jan Braun
2024-12-05 21:24                   ` Jan Braun
2024-12-05 23:15                     ` Re[2]: " Laurent Bercot
2024-12-04 20:09   ` Tanuj Bagaria

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