[Nut-upsdev] Joining forces with the Network UPS Tools

[Arjen de Korte]

Citeren Arnaud Quette <aquette.dev at gmail.com>:

>> Never mind, I already figured out a usage. If one of the machines connected
>> to an outlet gets stuck and you want to cycle the power on that outlet
>> (probably the main reason to use RPC's in the first place) you want to bring
>> down the other systems on that outlet down cleanly. Shutting down the whole
>> UPS/RPC system is currently the only option and this could be made more fine
>> grained.
> that's 1 of the 2 main use cases here.
> the other being that upsmon could monitor
> outlet.X.autoswitch.charge.low (where X is the outlet on which we
> subscribed the slave) against battery.charge to launch the shutdown
> without the need of upssched.

I'm afraid that's something that is not very practical to use. :-)

We would need to know in advance then how much time is remaining  
before the UPS reaches the 'autoswitch' level. Any mistakes here, and  
you risk that the UPS will switch off the power before the client has  
finished shutting down. As far as I'm concerned, the only use for  
'outlet.X.autoswitch.charge.low' is for loads that don't suffer from a  
sudden power loss. I don't think many systems running 'upsmon' fall  
into that category.

Regarding the use of multiple outlet systems, this could be solved in  
a driver independent way by creating a 'repeater' driver. That driver  
would connect to an existing driver socket and provide additional  
'pseudo' UPS'es with an additional command set that tells which  
parameters to override from the master UPS:

[master-ups]
    driver = usbhid-ups
    port = auto

[slave-1]
    driver = repeater
    port = master-ups
    desc = "Outlet 1"
    battery.charge.low = 30
    [...]

[slave-2]
    driver = repeater
    port = master-ups
    desc = "Outlet 2"
    battery.charge.low = 50
    [...]

You get the idea. The repeater would just listen to the master and  
adjust the 'ups.status' and 'battery.charge.low' (in this example)  
accordingly.

The advantage here is that we don't need any changes to the existing  
server or clients. It also doesn't need any changes to existing  
drivers, since they already support multiple connections on their  
driver socket.

Best regards, Arjen
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