A roll your own open source method works if you have a good low level understanding of what you are listening to and can organize your own alarm thresholds and groupings etc. Dealing with a large number of modbus/BACnet endpoints with vendor specific device profiles and PLC logic means the vendors backend systems will handle events and trend paterns better than what most facility teams can put together. However, the history retention data by itself will have more flexibility to do it yourself, I do agree with that.

There are open source projects like EdgeX and Fledge that can do this also

Wonderware historian, inductive automation ignition, and osi pi all can buffer data at a collection or edge node that it collects from a Plc and then forward it on to the central database historian when connectivity is present. Grafana might have a better web ui but they all offer some client for plotting.

I am curious in what regard nothing comes close to grafana? I am Currently paying a lot for citect and wonderware support across a couple dozen facilities.

We're a bit of a weird case in that we log data at 20Hz and 100Hz for prototypes, so we need custom queries and/or aggregation to reduce that down for display. We had a good chat with Inductive earlier this year, but even they said that might be a bit much for them. Other than that, though, Ignition is literally everything we want in a single product.

You are logging data in to grafana at 100 Hz from a Plc? That’s pretty quick for a plc, I’d definitely have either a tiny program or a fast periodic task to be generating new samples every 10 ms, although I’m sure there are faster PLCs out there than m340

Hehe, yeah. We run B&R PLCs which are fairly beefy Atom processors under the hood.

Telegraf can do this too, in a more limited capacity. It keeps an in-memory buffer of collected data points so if a write to an output fails it'll try again on the next interval without losing the data it has already collected.