Add is_running() method

[schloerke]

From @nbenn in https://community.rstudio.com/t/determine-whether-code-is-being-run-as-part-of-a-plumber-api/169128

I am looking for a reliable way of determining if code is being run "under" plumber. Something like what I believe shiny::isRunning() provides.

Thanks!

---

I'd like for it to take pr as a value and have it default to something like get_current_router() (or something) that possibly returns the currently running server and checks for a flag.

Could also have a method to return currently running plumber routers (if non-blocking) is implemented. And then the length of the routers could be checked for > 0.

[thomasp85]

Just to understand your thinking, you want a $is_running() method in pr, along with set_current_router()/get_current_router() to register a router globally as running. Then at last you want

is_running <- function(pr = get_current_router()) {
  pr$is_running()
}

[schloerke]

I believe a pr$isRunning() would be good to have. Maybe it can wrap around this logic?: https://github.com/rstudio/httpuv/blob/ff00e6b7c08d0bcf99f9d155bb16bed3a110a6cd/R/server.R#L60

Until there is non-blocking plumber execution, I believe we should wait to implement {set,get}_current_router()