Strengthen & Deploy

You will learn how to:

• Test the performance of your app
• Solidify Shiny apps using logging and debugging
• Deploy your app to a common Shiny platform

1 Deploying Shiny apps

• When running a Shiny app using runApp(), you host it on a local server, i.e. it remains in your local network
• Deploying a Shiny app means making your app available to other users!
• Deployment is the last step of app development

1.1 Strengthen

• Before it’s time to deploy, it’s a good idea to make sure your app passes the test of publicity
• Depending on the use case and target group, a deployed app should be:
  • fast: remote communication can make your app slower than on a local host
  • scalable: a high workload can crash your app
  • stable: errors also crash your app

1.2 Tools to strengthen

• There are a lot of Shiny extensions that help in strengthening a Shiny app, some of which we will address:
  • profvis: Profiles a Shiny app and creates performance visualizations
  • reactlog: Logs reactivity of your Shiny app and creates a dynamic reactive graph
  • shinyloadtest: Simulates a workload of users and determines how well your app is suitable for such a workload
  • shinytest: Creates snapshots and compares the visual appearance of them in subsequent runs
  • shiny::testServer(): Performs programmatic tests using the Shiny server logic of an app

1.3 Further resources

• Chapters 11 and 13 of Colin Fay’s Engineering Production-Grade Shiny Apps
• Chapters 21 and 23 of Hadley Wickham’s Mastering Shiny

2 Performance profiling

• Profiling means recording how much time and memory certain actions in your Shiny app need
• Useful for testing performance or speed of your app
• Performance profiling in Shiny can be done with the profvis package

2.1 Using the profvis package

• Simply run your app within a profvis::profvis() call:

profvis({runApp()})

Note

It is necessary to use runApp(), shinyApp() does not suffice!

• Then, perform some tasks in the Shiny app
• Close the app, and an HTML file will open that looks something like below:

3 Debugging Shiny apps

• Debugging Shiny apps is a unique challenge as Shiny code is not linear like regular R code
• Setting breakpoints is tricky and only supported in RStudio
• Here, we introduce three ways to debug a Shiny app:
  • Interactive debugging
  • Print debugging aka logging
  • Reactivity logging

3.1 Interactive debugging

• Interactive debugging comes from base R and works just like that
• Put a call to browser() somewhere in your server function
• Code execution is interrupted on the spot and you can explore the server function in a “frozen” state

Accessing input in Shiny browser call

3.2 Logging

• In base R, print debugging is frowned upon
• In Shiny, print debugging can be a nice way to understand errors along a reactivity path (or to understand reactivity in general)

3.3 Where am I?

• That is a question you might ask yourself occasionally when encountering errors in Shiny
• The whereami package can tell you exactly where you are
• Many R packages enable general logging (logging, logger, log4r), but whereami is especially suitable for Shiny

Logs from logger

Logs from whereami

3.4 Reactivity logging

• Reactivity logging means capturing and visualizing reactive dependencies in Shiny apps
• Useful for detecting overreactiveness and reactive instabilities
• Reactivity logging can be done using the reactlog package

3.4.1 Using the reactlog package

• Run reactlog::reactlog_enable() before running the Shiny app or set options(shiny.reactlog = TRUE)

• Do stuff in your Shiny app (particularly something that triggers dependencies!)

• Run shiny::reactlogShow() or reactlog::reactlog_show() after closing the app

• Alternatively, press Strg + F3 while the app is running

4 Deployment

• The deployment of Shiny apps is restricted to servers that support Shiny apps
• You can either set up a custom Shiny server or use a server provider

4.1 Where to deploy

Shiny app hosting

Name	Use	Requirements
shinyapps.io	Casual to professional applications	rsconnect R package
Posit Connect	Professional to corporate applications	rsconnect R package
Shiny Server	Setting up self-hosted Shiny servers	Shiny Server on a Linux server
ShinyProxy / Heroku	Deployment of containerized applications	Docker

4.2 shinyapps.io

• A common choice for more casual Shiny apps is shinyapps.io
  • It requires not much technical knowledge to deploy
  • It does not require a pre-existing infrastructure (e.g., a server)
  • It offers a free plan

Shinyapps.io plans

4.3 rsconnect

• Both for Posit Connect and shinyapps.io you need the rsconnect package
• rsconnect enables the communication between the Posit services and R

• rsconnect is built around the deployApp(), deployAPI() and deployDoc() functions

4.4 Creating an account

• Before being able to deploy to Shinyapps, we need an account
• Accounts can be created per Email or using Google, Github or Clever

Shinyapps.io sign-up

4.5 Connecting R to shinyapps.io

• Just with any interface, linking works using Tokens and Secrets
• On your shinyapps dashboard, navigate to Account -> Tokens on the sidebar
• Click on “Add Token”
• Click on “Show” next to your newly created token
• Paste the code into your console and execute

Shinyapps token to connect with rsconnect

4.6 Deploy!

• To verify that the verification process was successful we run:

rsconnect::accounts()

• Finally, to deploy an app, we simply run deployApp() to deploy an app.R in the current working directory to shinyapps.io:

rsconnect::deployApp()