I mentioned on the Fediverse a while back that we have air conditioners on our internal network . Well, technically what we have on the internal network is separate (and optional) controller devices that connect to the physical AC units themselves, but as they say, this is close enough. Of course there's a story here :

Why do we have networked AC controllers? Well, they control portable AC units that are in our machine rooms for emergency use, and having their controllers on our internal network means we can possibly turn them on from home if the main room AC stops working out of hours, on weekends, etc.

(It would still be a bad time, just maybe a little less bad.)

Our machine rooms are old ( cf ) and so are their normal AC units. Over the years we've had enough problems with these AC units that we've steadily accumulated emergency measures. A couple of years ago, these emergency measures reached the stage of pre-deploying wheeled portable AC units with their exhaust hoses connected up to places where they could vent hot air that would take it outside of the machine room.

Like most portable ACs, these units are normally controlled in person from their front panels (well, top panels). However, these are somewhat industrial AC units and you could get optional network-accessible controllers for them; after thinking about it, we did and then hooked the controllers (and thus the ACs) up to our internal management network. As I mentioned, the use case for networked control of these AC units is to turn them on from home during emergencies. They don't have anywhere near enough cooling power to cover all of the systems we normally have running in our machine rooms, but we might be able to keep a few critical systems up rather than being completely down.

(We haven't had serious AC issues since we put these portable AC units into place, so we aren't sure how well they'd perform and how much we'd be able to keep up.)

These network controllers can get status information (including temperatures) from the ACs and have some degree of support for SNMP, so we could probably pull information from them for metrics purposes if we wanted to. Right now we haven't looked into this, partly because we have our own temperature monitoring and partly because I'm not sure I trust the SNMP server implementation to be free of bugs, memory leaks, and other things that might cause problems for the overall network controller.

(Like most little things, these network controllers are probably running some terrifyingly ancient Linux kernel and software stack. A quick look at the HTTP server headers says that it's running a clearly old version of nginx on Ubuntu, although it's slightly more recent than I expected.)