r - Shiny: How to stop processing invalidateLater() after data was abtained or at the given time

Question

I want to keep reflashing until 10:05, after 10:05 I got the tplus0_dt and stop to processing invalidaterLater().

Before 10:00, tplus0_dt doesn't exist, so I need to keep reflashing until 10:05. After 10:05, it is no need to refalsh, and when the tplus0_dt becomes very lage the invalidaterLater() will effects the displaying of table1, the screen and plots go GRAY every 1 seconds so it looks like the page is dead while the updating occurs.

So how can I do to stop processing the invalidateLater() and keep showing the data after 10:05? Thanks for help! My example code were below.

require(shiny)
require(data.table)
app <- shinyApp(
    server = function(input, output, session){
            get_tplus0_data <- reactive({
                    time <- substr(as.character(Sys.time()), 12, 16)
                    invalidateLater(1000)
                    if(time >= "10:05"){
                            # tplus0_dt<-data.table(read.csv("/data/df_highest_after_signal.csv",header = T, sep = ",", stringsAsFactors = F)) 
                            tplus0_dt<- data.table(a = c(1, 2, 3, 4), b = c(3, 4, 5, 8)) 
                            return(tplus0_dt)
                    }

            })
            output$table1 <- renderTable({get_tplus0_data()})
    },
    ui = fluidPage( tableOutput("table1")  )
)

runApp(app)

Answer 1

How about you override the function to your needs?

If you enter invalidateLaterNew in the console, the code of the function will be printed.

To overwrite a function within a package this post will help: Override a function that is imported in a namespace

Then you will have to consider that the functions .getReactiveEnvironment() and timerCallbacks() are not accessible outside the namespace. But you can call them like this: shiny:::.getReactiveEnvironment()

Bring it together:

You add an additional parameter (e.g. update), which will enable you to stop the invalideLater() whenever you want.

invalidateLaterNew <- function (millis, session = getDefaultReactiveDomain(), update = TRUE) 
{
  if(update){
    ctx <- shiny:::.getReactiveEnvironment()$currentContext()
    shiny:::timerCallbacks$schedule(millis, function() {
      if (!is.null(session) && session$isClosed()) {
        return(invisible())
      }
      ctx$invalidate()
    })
    invisible()
  }
}

unlockBinding("invalidateLater", as.environment("package:shiny"))
assign("invalidateLater", invalidateLaterNew, "package:shiny")

Example:

I used the example given in ?invalidateLater to demonstrate the effect: (invalidateLater will stop when input$nis bigger than 800. So you can adapt this example to your time restriction). I decided not to use your time restriction example as it wouldnt be that handy to test ;)

ui <- fluidPage(
  sliderInput("n", "Number of observations", 2, 1000, 500),
  plotOutput("plot")
)

server <- function(input, output, session) {

  observe({
    # Re-execute this reactive expression after 1000 milliseconds
    invalidateLater(1000, session, input$n < 800)
    # Do something each time this is invalidated.
    # The isolate() makes this observer _not_ get invalidated and re-executed
    # when input$n changes.
    print(paste("The value of input$n is", isolate(input$n)))
  })

  # Generate a new histogram at timed intervals, but not when
  # input$n changes.
  output$plot <- renderPlot({
    # Re-execute this reactive expression after 2000 milliseconds
    invalidateLater(2000, session, input$n < 800)
    hist(rnorm(isolate(input$n)))
  })
}

shinyApp(ui, server)