write ws_relay.py

[ahuss12]

potential python script that spawns data_stats -D , reads each JSON line on stdout and broadcast it to all Websocket clients.

[garyjg]

This idea has lots of possibilities, and I think it makes more sense than implementing the websocket server in NIDAS in C++. We have done something similar for the isfcallab software prototype, where the dsm.py module starts data_stats and reads the JSON samples from a pipe, similar to the example script showjson.py does it.

In this case, I think the "python script" could just be the python web app using a framework like FastAPI. The web app can run data_stats and read from the pipe, then it can know when new updates are available and potentially send them directly to the client over websockets. data_stats does not need to run in the background with systemd if the web app runs it itself.