Is it possible to stop execution of R code inside shiny (without stopping the shiny process)?

Dean Attali

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Jun 4, 2015, 6:59:29 PM6/4/15

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(x-post from SO because of 0 answers)

Let's say I have a shiny app that has a function that can take a long time to run. Is it possible to have a "stop" button that tells R to stop the long-running call, without having to stop the app?

Example of what I mean:

analyze <- function() {
  lapply(1:5, function(x) { cat(x); Sys.sleep(1) })
}

runApp(shinyApp(
  ui = fluidPage(
    actionButton("analyze", "Analyze", class = "btn-primary"),
    actionButton("stop", "Stop")
  ),
  server = function(input, output, session) {
    observeEvent(input$analyze, {
      analyze()
    })
    observeEvent(input$stop, {
      # stop the slow analyze() function
    })
  }
))

Frédéric Moser

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Dec 29, 2015, 2:41:15 PM12/29/15

to Shiny - Web Framework for R

I've posted something on SO about this :

shiny function interruption

John Luis

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Feb 6, 2016, 12:12:37 AM2/6/16

to Shiny - Web Framework for R

I have this exact same need, so reposting Dean's old question. I want to give the user a Stop button so they can stop a call midway if it's taking long.

I tried stop() but it doesn't interrupt the function that's running.

Thoughts?

Thanks!

Joe Cheng

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Feb 6, 2016, 12:17:35 AM2/6/16

to John Luis, Shiny - Web Framework for R

It's not possible right now, but last week I would've told you it would never be possible, whereas now I can think of a way to possibly implement this once we have done our next round of changes on httpuv. No promises though and in the meantime I can't think of any workaround.

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John Taveras

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Feb 8, 2016, 9:34:21 AM2/8/16

to Joe Cheng, Shiny - Web Framework for R

Sounds great! Fingers crossed that you find a way.

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