Scaling Shiny with session affinity on Heroku

Helo Shiny Team.

I noticed that the Other hosting options chapter mentions Heroku and session affinity as something that does not quite work as expected:

We had high hopes for Heroku, as they have a documented option for session affinity. However, for reasons we don’t yet understand, the test application consistently fails to pass. We’ll update this page as we find out more.

You also mentioned that if you beat us to a successful deployment, please get in touch about your experiences! So here it is.

I used the test application and its port to R and tested this feature with a containerized setup. I can report that session affinity works as expected on Heroku.

Here are some resources with details about implementation:

• https://github.com/analythium/shiny-load-balancing
• https://hosting.analythium.io/scaling-shiny-apps-for-python-and-r-sticky-sessions-on-heroku/
• https://youtu.be/-bCtShSHsfA

Review the Other hosting options chapter linked in the issue, along with the referenced load-balance test application and deployment resources. Update the Heroku session-affinity guidance to reflect the reported successful deployment, with the linked implementation details supporting the revised documentation.