Rselenium can't connect to running shiny app

I figured it out with a LOT OF HELP from @jdharrison.

First make docker compose file (be careful with indentations - one indention must be 2 spaces) and save as docker-compose.yml:

version: '2'services:  ropensci:    image: rocker/ropensci    ports:      - "8788:8787"    links:      - selenium:selenium      - shiny:shiny  selenium:    image: selenium/standalone-chrome    ports:      - "4445:4444"    links:      - shiny:shiny  shiny:    image: rocker/shiny    container_name: shiny    volumes:      - ~/Users/username/services/volumes/shiny/apps:/srv/shiny-server/      - ~/Users/username/services/volumes/shiny/logs:/var/log/      - ~/Users/username/services/volumes/shiny/packages:/home/shiny/

or download: https://codeshare.io/2j4yLB

then run docker-compose up from folder where docker-compose.yml file is.

• Add your apps to /home/username/services/volumes/shiny/apps
• To navigate to your app from selenium use http://shiny:3838/myapp

To check if it works you can save below code as app.R in: ~/Users/username/services/volumes/shiny/apps/example/:

library(shiny)server <- function(input, output) {  output$distPlot <- renderPlot({    hist(rnorm(input$obs), col = 'darkgray', border = 'white')  })}ui <- fluidPage(  sidebarLayout(    sidebarPanel(      sliderInput("obs", "Number of observations:", min = 10, max = 500, value = 100)    ),    mainPanel(plotOutput("distPlot"))  ))shinyApp(ui = ui, server = server)

and run:

library(RSelenium) remDr <- remoteDriver(remoteServerAddr = "selenium", port = 4444L, browser = "chrome") remDr$open()remDr$navigate(url = "http://shiny:3838/example")remDr$screenshot(display = TRUE)

If everything is ok you should see screenshot:

There are a number of ways to achive this. Easiest way is to run docker in --net=host mode. This will mean mean selenium server runs on the default port 4444

docker run -d --net=host selenium/standalone-chrome&

Your docker container will now have access to the HOST localhost.

To run on a non default PORT you can pass docker a selenium env variable:

docker run -d --net=host -e SE_OPTS="-port 4445" selenium/standalone-chrome