Concurrent R-Shiny

This repository provides examples on how to deploy R-Shiny applications in a Kubernetes environment with concurrency/sticky sessions in mind. These examples were created to support a paper presented at PEARC24.

Prerequisites

• Experience working with Containers and Kubernetes
• A Kubernetes Cluster
• Traefik Ingress Controller installed

R-Shiny Application

We built our R-Shiny container images based upon the rocker/shiny:4.3.1 image. Details about this image and other available images can be found here:

https://rocker-project.org/images/versioned/shiny.html

For the examples in this repository, we'll be using the unaltered rocker/shiny:4.3.1 image to represent our R-Shiny application.

NOTE: rocker/shiny:4.3.1 is only available in the x86_64 architecture.

Installation

First, we apply the rshiny-demo-app.yml manifest to kubernetes which creates a namespace called rshiny-demo-app, a service called rshiny-demo-app, and a deployment called rshiny-demo-app. This deployment will be configured with two replicas to show sticky sessions functioning as expected.

kubectl apply -f rshiny-demo-app.yml

If you want to deploy the application to the root of your domain (ex. http://example.com/), then you can use the ingress-root.yml manifest. This will create an ingress resource that will route traffic from the root of your domain to the R-Shiny application.

kubectl apply -f ingress-root.yml

If you want to deploy the application to a subpath of your domain (ex. http://example.com/rshiny-demo-app), then you can use the ingress-subpath.yml manifest. This will create an ingress resource that will route traffic from the /rshiny-demo-app subpath to the R-Shiny application.

kubectl apply -f ingress-subpath.yml

When you access the domain, you should see a cookie called RShinyDemoAppStickyCookie created in your browser. This cookie is used to enable sticky sessions to a specific pod. If you delete this cookie, you'll see that the session is no longer sticky and you're routed to a different pod. You can determine which pod you are connected to by looking at the logs for each pod.