Pause queue

[rfaelens]

I am using future_promise() to run calculations that sequentially get better and better. Results are displayed in a shiny app. This works great.

However, we would need a way to pause and resume a WorkQueue. I have built a custom PauseWorkQueue class that adapts can_proceed(), but starting the WorkQueue is subject to all Delay objects running out.

Is there a better way to do this?

Current solution:

PauseQueue <- R6Class("PauseQueue",
                      inherit = promises:::WorkQueue, # Hier geven we de ouderklasse aan
                      public = list(
                        running = TRUE,
                        queue=fastmap::fastqueue(),
                        initialize = function() {
                          super$initialize(can_proceed=function(){
                            future::nbrOfFreeWorkers() > 0 && self$running
                          }, queue=self$queue)
                        },
                        stop = function() {
                          self$running <- FALSE
                        },
                        start = function() {
                          self$running <- TRUE
                        },
                        isRunning = function() {
                          self$running & self$queue$size() > 0
                        }
                      )
)
queue <- PauseQueue$new()
N <- 10
todo <- purrr::map(seq_len(N), function(i){
 f <- promises::future_promise(
   expr={
     cat("Evaluating... ",i,"\n")
     Sys.sleep(0.5)
     i
   },
   queue=queue
 )
})

queue$stop()