[Nut-upsdev] MGE NMC and NutShutdownModule (and other stuff)

[Arjen de Korte]

Citeren Marco Chiappero <marco op absence.it>:

> Yes, that's why I was asking about mge-xml subdriver vs. new driver  
> choice.  However my idea was to keep things easy and to basically  
> create a NSM clone for NUT.

That is where the problem lies. Currently, the upsd server connects to  
drivers in a one driver (instance), one UPS mode:

     UPS-1 --- driver-A ----+         +---- upsmon client
                            |         |
     UPS-2 --- driver-B --- upsd server --- upsmon client
                            |         |
     UPS-3 --- driver-C ----+         +---- upsmon client

So each UPS (or outlet, for the clone driver) is exactly one  
connection and that's what the socket protocol we use is built on (and  
for this reason, we need to use the clone driver if we want to use the  
load segment switching).

For an NSM clone, this scheme doesn't work anymore, since one driver  
connects to many outlets (or even UPS devices):

     UPS-1 ----+                        +---- upsmon client
               |                        |
     UPS-2 --- NSM driver --- upsd server --- upsmon client
               |                        |
     UPS-3 ----+                        +---- upsmon client

So this will require 'some' work. And what becomes immediate clear in  
the above picture, it probably doesn't make much sense to change the  
socket protocol between drivers and server, but instead integrating  
the NSM functionality in the server would be much easier.

Then the question remains, why would we want this in the first place?  
The NMCs are already servers themselves so adding a upsd server will  
only complicate matters. Instead, you could do away with NUT entirely,  
by using an appropriate NSM client that directly talks to the NMC and  
not have to bother setting NUT up at all. I haven't seen a compelling  
argument that adding NUT here is a good idea.

Best regards, Arjen
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