From: Paul Sopka <psopka@sopka.ch>
To: supervision@list.skarnet.org,
Laurent Bercot <ska-supervision@skarnet.org>
Subject: Re: Have an external script wait for a oneshot service
Date: Fri, 6 Dec 2024 13:41:34 +0100 [thread overview]
Message-ID: <e5a58bbd-b00f-4756-bd57-662d09456524@sopka.ch> (raw)
In-Reply-To: <em06859e26-3823-444a-9cba-a3e13c5d06da@7c9fd885.com>
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> Exactly. That's the YAGNI principle: don't try to solve problems you
> haven't encountered yet. Chances are you'll actually never encounter
> them. Adding complexity in the name of "just in case" is overengineering
> and it will only worsen your design.
We now have two examples of application from the other mails.
> And if I have learned anything about users, it's that most of your
> users will have trouble understanding what a supervised service is,
> and if you start talking about them about s6-rc services, their brain
> will start melting and they'll run away from your system as fast as
> they can. And they won't be wrong.
When I talked about "users", I mean people actually *using* these tools,
meaning s6, s6rc, execline, POSIX tools, ... hence power users and
distribution maintainers.
People using their computers only to consume media or write documents
(whom I will refer to as consumers),
will use Windows, MacOS or, in the best case, a highly managed Linux
distro anyway.
Thus I do not consider them, since they will never interact with
service management directly anyway.
I therefore try to make life as easy as possible for power users
and distribution maintainers, who manage their own supervision trees
or setup the presets for said managed distros respectively.
> The user has a supervision tree. They can install their longrun directly
> in it. They don't need s6-rc for that. Pure s6 is enough.
> Their service will run as long as they keep it there. They can stop
> it with s6-svc. Or s6-svunlink.
Assuming s6-rc is used for the main supervision tree and on login,
which is fair, since the very thing we discuss about is part of my project
doing all of that with s6-rc,
this would cause users to need to learn s6 additionally to s6-rc,
when s6-rc can be used for all cases.
> You want to run s6-rc at login time, sure, I can totally see where i
> can be beneficial there. But earlier? Even systemd doesn't run user
> stuff before a user logs in. And if *they* don't do it, it means that
> there are ZERO use cases.
This is an argumentum ad verecundiam.
Systemd is fundamentally flawed in other places too.
> And what is preventing that? The fact that your default bundle does not
> include the services that the user has defined themself. This should give
> you a hint that this design goes against what supervision is supposed to
> be doing, and thus, that it's not a good design. Whatever longrun the
> user wants to have survive a reboot should survive a reboot and the
> user shouldn't need a PhD to accomplish that.
> If the user has installed their service in the pure s6 way with e.g.
> one (1) call to s6-svlink, it works: after a reboot, the snooze will
> be back up.
We have, due to my poor wording, a misunderstanding here:
Said "default" bundle is part of the user's user-tree,
it is entirely under his control and offers the user a way to have
user-services started at boot time.
I have assumed that the scan-directory of the user-tree is mounted tmpfs.
This would require additional support in 1a/2a
to save the state of the scan-directory on shutdown and load it on boot.
Or let s6-rc-init and s6-rc do this work, by adding the service to the
user-tree bundle "default"
and running s6-rc for each user-tree at boot.
> It's more inconvenient, complex and inconsistent because you want to
> keep the framework that makes it so. Remove a little more and you'll
> have something elegant again.
What is the "little more" you are talking about?
> Little to no cost? This whole thread is about the costs! And from my
> perspective, "probably going to be useful at some point" is a pretty
> light argument, it's definitely not going to outweigh "too complex to
> make work properly".
The cost is, quoting myself, one(mutually exclusive) of the following:
> - S1 Script s6-fifodir functionality in bot the system-oneshot
> 1b/2c and the script L.
>
> - S2 Add a readiness api for s6-rc oneshots like s6 longruns have
> and wait for that of system-oneshot 1b/2c in the script.
>
> - S3 Have the script L do the same as system-oneshot 1b/2c:
> - 1bi/2ci Prepare the live directory for the user-tree
> (preferably under /run/user/${USER}).
> - 1bii/2cii Start "s6-rc-init -b" and "s6-rc start login".
> Utilizing blocking locks and tests to work parallel to
> system-oneshot 1b/2c.
> This can only be done if the script is ran through PAM,
> since 1bi/2ci requires root privileges.
I do not see where this exceeds "little".
Regards
Paul
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next prev parent reply other threads:[~2024-12-06 12:41 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
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 [this message]
2024-12-06 15:43 ` 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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