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difference between operating Systems in a multisession shiny progressor  #164

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@wstvcg

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@wstvcg

The following minimal code seems to works flawlessly with handlers("progress") both in linux and windows.

handler_shiny only seems to work in parallel with a windows os.
The linux shiny app only shows half of the progress steps in a sequential order.

Any advice?

library(shiny)
 library(progressr)
 library(purrr)
 library(furrr)
 library(tibble)


 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 my_fct <- function(x,
                    workers = 2
 ) {

   my_steps <- nrow(dplyr::bind_rows(x))
   p <- progressor(steps = my_steps * workers)
   set.seed(123)
   future::plan(multisession, workers = workers)

   x |>
     furrr::future_walk(\(list) {
       list[[1]] |>
         purrr::walk(\(item) {
           Sys.sleep(.25)
           p(message = item)
         })

     })
 }
 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 my_list <- list(one = tibble(a = as.character(1:20)),
                 two = tibble(a = letters[1:20]))
 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 #future::plan(multisession, workers = 2)
 handlers("progress")
 system.time(progressr::with_progress(my_list |> my_fct()))
 #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 shinyApp(
   ui = fluidPage(plotOutput("plot")),

   server = function(input, output) {
     output$plot <- renderPlot({

       progressr::withProgressShiny(
         message = "Calculation in progress",
         detail = "Starting ...",
         value = 0,

         handlers = c(shiny = handler_shiny,
                      progressr::handlers(default = 'progress')),
         {
           result <- my_list |>
             my_fct()
         plot(cars)
         }

       )
     })

   }
 )

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