Knowledge of plain old CGI on a web server seems lost due to fancy frameworks?

eh I just never learned it. I'm a robotics engineer and I tend to write programs in Python (or less commonly now, C++) to run in a loop and deal with local hardware. The way that web servers operate in a stateless multithreaded way involves some peculiarities that I always find a little tricky.

I sometimes transfer data with curl via a url which does not exist, but where a script running on the server watches the server's error log and extracts data from those entries.

Hey that's a nice trick! I already have a server running discourse. Maybe I can sneak something in there. Though it looks like someone's suggestion of https://healthchecks.io/ might do what I need.