Memory leak by using observeEvent

Question

I get cumulating memory using the following code. Every time I switch between the action button 1 and 2 the used memory increases.

library(ggplot2)
library(shiny)
library(lobstr)

ui <- navbarPage("Test",fluidPage(fluidRow(
                     column(width = 1, actionButton("action_input_1", label = "1")), 
                     column(width = 1, actionButton("action_input_2", label = "2")),
                     column(width = 10, plotOutput("plot", width = 1400, height = 800)))))

server <- function(input, output) {
  # 1
  observeEvent(input$action_input_1, {
    output$plot <- renderPlot({
      plot(rnorm(100))
    })
    print(cat(paste0("mem used 1: ", capture.output(print(mem_used())),"\n")))
  })

  # 2
  observeEvent(input$action_input_2, {
    output$plot <- renderPlot({
      plot(rnorm(1000))
    })
    print(cat(paste0("mem used 2: ", capture.output(print(mem_used())),"\n")))
  })
}
shinyApp(ui, server)

Due to a suggestion in this post, I have tried not to use observeEvent. Here is the server function:

server <- function(input, output) {
  # 1
  output$plot <- renderPlot({
    input$action_input_1
    plot(rnorm(100))
    print(cat(paste0("mem used 1: ", capture.output(print(mem_used())),"\n")))
  })

  # 2
  output$plot <- renderPlot({
    input$action_input_2
    plot(rnorm(1000))
    print(cat(paste0("mem used 2: ", capture.output(print(mem_used())),"\n")))
  })
}

Here the memory does not increase, but only the second action button (=the last block of code?) is working. Is there a solution to prevent memory leak and get both buttons working?

Answer 1

How about using reactiveVal :

reactiveData <- reactiveVal(NULL)
observeEvent(input$action_input_1, reactiveData(rnorm(100)))
observeEvent(input$action_input_2, reactiveData(rnorm(1000)))
output$plot <- renderPlot(plot(reactiveData()))

Reactive values have a little different syntax:

reactiveData <- reactiveValues(rnorm = NULL, bool_val = NULL) 

observeEvent(input$action_input_1,  {# reactiveData(rnorm(100), bool_val <- TRUE)) 
   reactiveData$rnorm <- rnorm(100)
   reactiveData$bool_val <- TRUE
})

observeEvent(input$action_input_2, { #reactiveData(rnorm(1000), bool_val <- FALSE)) 
  reactiveData$rnorm <- rnorm(1000)
  reactiveData$bool_val <-  FALSE
})

output$plot <- renderPlot(plot(reactiveData$rnorm))

Though your variables are changing in concert, so you could technically still use reactiveVal

reactiveData <- reactiveVal(list(rnorm = NULL, bool_val = NULL)) 

observeEvent(input$action_input_1, reactiveData(list(rnorm = 100, bool_val = TRUE)))

observeEvent(input$action_input_2, reactiveData(list(rnorm = 1000, bool_val = FALSE)))

output$plot <- renderPlot(plot(reactiveData()$rnorm))