What is the problem?
I'm an experienced developer but a newbie with OctoPrint, so I don't yet have a good mental model of the software architecture and signal flow. Whenever OctoPrint starts up, I'd like to be able to trigger a script to launch some of my own tools in the background, but I don't want to hack something together of my own if there's already a standard way to do this.
I've looked through the documentation and forums without seeing anything obvious, and I don't see any plug-ins that do it either. Is there some existing mechanism I haven't found yet, or a method other people are using to accomplish this?
FTR, I'm running OctoPrint 1.5.3 on OctoPi 0.18.0 under Python 3.7.3 on a 3B+.