shinyloadtest package and the accompanying
shinycannon command line tool make it possible to load test deployed Shiny apps. Load testing helps developers and administrators estimate how many users their application can support. If an application requires tuning, load testing and load test result analysis can be used to identify performance bottlenecks and to guide changes to infrastructure, configuration, or code.
Scientific load testing helps put to rest the common misconception that "Shiny doesn’t scale". As rstudio::conf(2018) Sean Lopp presented on Scaling Shiny which shows how to to horizontally scale an app to handle tens of thousands of users.
To perform a load test you’ll need two pieces of software:
shinyloadtest is an R package used to generate recordings and analyze results. You should install it on your development machine with
shinycannon is a command-line used to replay recordings in parallel. You can install it on your development machine for testing, but for best results we recommend installing it on a server, and preferably not the one the application under test is also on. See installation instructions for operating specific install instructions..
The process for load testing a Shiny application consists of three steps:
Rinse and repeat as necessary. Each step is described below.
Record a session using
shinyloadtest::record_session(), which takes the URL of the deployed application as an argument:
Running the function will open a browser displaying the app. Once open, interact with the application as a typical user might then close the browser. After closing the app, a file (
recording.log by default) will be created that contains a recording of the session. This recording will serve as the basis for the load test.
With the recording in hand, we’re ready to run the load test. The actual test is conducted outside of R using the
shinycannon command-line tool. You can run it using your system’s terminal or console program, or you can run it from the RStudio terminal tab. A typical run looks like this:
See the shinycannon article for details.
This self contained html report will be opened in your browser for inspection. For further analysis explanation, please visit Analysing load test logs.