Quit a Plumber API once a condition is met

Question

I am trying to run a Plumber API inline to receive an input, and once the proper input is received and a specified condition is met, the input is returned to the globalenv and the API closes itself such that the script can continue to run.

I've specified a condition within a @get endpoint that calls quit(), stop() etc, none of which successfully shut down the API.

I've attempted to run the API in parallel using future such that the parent script can close the Plumber API.

It appears that there isn't actually a method in the Plumber API class object to close the Plumber API, and the API can't be closed from within itself.

I've been through the extended documentation, SO, and the Github Issues in search of a solution. The only semi-relevant solution suggested is to use R.Utils::withTimeout to create a time-bounded timeout. However, this method is also unable to close the API.

A simple use case: Main Script:

library(plumber)
code_api <- plumber::plumb("code.R")
code_api$run(port = 8000)

code.R

#' @get /<code>
function(code) {
  print(code)
  if (nchar(code) == 3) {
    assign("code",code,envir = globalenv())
  quit()}
  return(code)
}
#' @get /exit
function(exit){
  stop()
}

The input is successfully returned to the global environment, but the API does not shut down afterward, nor after calling the /exit endpoint.

Any ideas on how to accomplish this?

Answer 1

You could look at Iterative testing with plumber @Irène Steve's, Dec 23 2018 with:

• trml <- rstudioapi::terminalCreate()
• rstudioapi::terminalKill(trml)

excerpt of her article (2nd version of 3):

.state <- new.env(parent = emptyenv()) #create .state when package is first loaded

start_plumber <- function(path, port) {
    trml <- rstudioapi::terminalCreate(show = FALSE)
    rstudioapi::terminalSend(trml, "R\n") 
    Sys.sleep(2)
    cmd <- sprintf('plumber::plumb("%s")$run(port = %s)\n', path, port)
    rstudioapi::terminalSend(trml, cmd)

    .state[["trml"]] <- trml #store terminal name
    invisible(trml)
}

kill_plumber <- function() {
    rstudioapi::terminalKill(.state[["trml"]]) #access terminal name
}