[Nut-upsuser] Is a timer a file?

[Arnaud Quette]

Hi Roger

2017-03-21 19:34 GMT+01:00 Roger Price <roger at rogerprice.org>:

> On Tue, 21 Mar 2017, Arnaud Quette wrote:
>
> Hi Roger,
>>
>> reviving this discussion, since we have a Github ticket for 2.7.5:
>> https://github.com/networkupstools/nut/issues/293
>>
> ...
>
>> I've made some additions to clarify things on the timer, and complete the
>> script:
>> https://github.com/networkupstools/nut/compare/upssched-doc?expand=1
>>
>
> Hi Arnaud, Your change to the documentation clears up what I had
> mis-understood.  The new text makes it clear that the upssched timers are
> an in-memory device, and that they can only be turned on and off with
> upssched.conf declarations such as
>
>     AT ONBATT * START-TIMER onbattwarn 30
>     AT ONLINE * CANCEL-TIMER onbattwarn
>

thanks for your confirmation. I'll check to merge that PR.


>       Is there some other way of forcing routine cancel_timer from a
>> script or a configuration file?
>>
>> this is the last point to address, but I'd need to better understand
>> prior to potentially taking action:
>> theoretically, each event that triggers a timer (like ONBATT) has a
>> counterpart to cancel it (like ONLINE).
>> Ex (from the doc):
>>     AT ONBATT * START-TIMER onbattwarn 30
>>     AT ONLINE * CANCEL-TIMER onbattwarn
>>
>> So is there any use case we're missing here?
>>
>
> My use case was for a UPS unit which gave transient stupid status changes
> such as "OL DISCHARG CHARG LB" when the battery was 100% charged.  It was
> an old MGE unit which has since died.
>
> When the stupid status change occured, the LB began a system shutdown.  To
> overcome this unwanted stutdown, I wanted to start a 5 second timer, and
> when this ran out, upssched-cmd would review the situation, and decide if a
> shutdown was really needed.  If it was not needed, I had to cancel the
> system-shutdown timer.  I mistakenly assumed that such a timer was a file,
> and that it was sufficient to erase the file.
>
> To solve the problem of cancelling an arbitrary timer from a script such
> as upssched-cmd, I submitted a proposal to nut-upsdev:
>
>    [Nut-upsdev] Proposal for technique to stop a timer at any moment
> https://lists.alioth.debian.org/pipermail/nut-upsdev/2016-July/007202.html
>
> and a set of patches :
>
> https://lists.alioth.debian.org/pipermail/nut-upsdev/2016-July/007203.html
> https://lists.alioth.debian.org/pipermail/nut-upsdev/2016-July/007204.html
>
> The technique is very general and is to send SIGUSR1/SIGUSR2 to the upsd
> daemon.  SIGUSR1 and SIGUSR2 are events just like ONBATT and ONLINE. The
> patch runs successfully on my opensuse 13.2 box, and solves my problem. In
> upssched.conf I now have declarations such as
>
>    AT SIGUSR1 * CANCEL-TIMER shutdown-timer
>
> Will my patches be included in NUT?
>

Thanks for sharing your use case, and the rationales behind.
First, the base point is to be able to cancel a timer anytime, from a
command-line, which makes sense (as an extension, the opposite may also be
true, to start a timer lively, without the event coming from upsmon).

I've quickly checked your 2 patches.
The solution seems to me not broad enough for injecting upstream. This
works nice for a single device / UPS setup, but would not make it when
there are more devices, as I get it.

At first sight, I would more see something injecting into the PIPEFN fifo,
i.e. acting the same way upsmon would when calling upssched with the
upsname and the triggering event.
I think that this can be solved more easily with tools like socat or nc,
sending the command directly to the pipe.
For example, to cancel the timer "shutdown-timer" from the upssched-cmd
script, you would:

       echo "CANCEL shutdown-timer" | socat -
UNIX-CLIENT:/var/run/nut/upssched.pipe

Please tell me back if such solution would make it for you.

I also realize that the distributed sample configuration and scripts do not
fully match the doc.
I'll make another round of update for this, still on the same branch.
I would warmly welcome your help to complete the documentation, both with
part of your patches that make sense, along with the above solution if it's
good too.

cheers,
Arno
-- 
Eaton Data Center Automation Solutions - Opensource Leader -
http://42ity.org
NUT (Network UPS Tools) Project Leader - http://www.networkupstools.org
Debian Developer - http://www.debian.org
Free Software Developer - http://arnaud.quette.fr
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