supervision - discussion about system services, daemon supervision, init, runlevel management, and tools such as s6 and runit
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From: Steve Litt <slitt@troubleshooters.com>
To: supervision@list.skarnet.org
Subject: Re: Dependencies in S6
Date: Wed, 21 Oct 2020 15:14:45 -0400
Message-ID: <20201021151445.71486a0b@mydesk.domain.cxm> (raw)
In-Reply-To: <em81fd4f46-86a3-4d4d-86db-94865393f2f7@elzian>

On Wed, 21 Oct 2020 13:26:25 +0000
"Laurent Bercot" <ska-supervision@skarnet.org> wrote:

>   "A is ready" means:
>    - if A is a oneshot: when the script has completed
>    - if A is a longrun:
>      * if there is a notification-fd file in the service definition
> directory: when the daemon has notified readiness
>      * if there is no such file: as soon as the run script has started
> (which is not a good readiness indicator; it is akin to starting B
> _right after A_, essentially in parallel, so you may have race
> conditions here - which is why you should always use readiness
> notifications.)

I seem to remember that s6 also has specially named shellscript to
determine dependency readiness. So, for instance, process B requires a
functioning network, the shellscript would contain a ping command or an
ip command. I do this all the time, informally.
 
SteveT

Steve Litt 
Autumn 2020 featured book: Thriving in Tough Times
http://www.troubleshooters.com/thrive

      reply	other threads:[~2020-10-21 19:14 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-21 10:10 Amaresh Kotekal
2020-10-21 13:17 ` Guillermo
2020-10-21 13:23 ` Crest
2020-10-21 13:26 ` Laurent Bercot
2020-10-21 19:14   ` Steve Litt [this message]

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supervision - discussion about system services, daemon supervision, init, runlevel management, and tools such as s6 and runit

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