ShinyProxy not honoring HTTP_X_FORWARDED_PREFIX for proxied calls

ShinyProxy
1

Hi Team,

We are using ShinyProxy (3.2.2) behind IIS with URL Rewrite enabled.

The initial application requests correctly honor the HTTP_X_FORWARDED_PREFIX header and the forwarded path is applied as expected.

However, when requests are redirected to the following ShinyProxy internal endpoints:

/app_proxy/…

/api/proxy/…

/heartbeat

/app_i/…

the HTTP_X_FORWARDED_PREFIX header is not being applied anymore.

Current Behavior (example)

Initial Request (correct):

/APPs/ActiveSession/Shinyapps/app/MyAnalyticsApp/

After redirection (incorrect):

/app_proxy/5d9a4c81-7b33-4a73-83d3-8f0dc4ff7b75/

Expected Behavior

We want all requests to maintain the prefix:

/APPs/ActiveSession/Shinyapps/app_proxy/5d9a4c81-7b33-4a73-83d3-8f0dc4ff7b75/

The goal is to ensure that every call routed through IIS preserves a consistent URL pattern.

Current ShinyProxy configuration (application.yaml)

server:

useForwardHeaders: true

forward-headers-strategy: framework

proxy:

title: Shiny Proxy

port: 8211

container-backend: docker

authentication: none

context-path: /shinyapps

hide-navbar: true

Question

Is there any ShinyProxy configuration option or recommended setup that ensures internal proxy routes (/app_proxy, /api/proxy, /heartbeat, /app_i) also honor the HTTP_X_FORWARDED_PREFIX header?

Any guidance or best practices for running ShinyProxy behind IIS with URL Rewrite would be greatly appreciated.

Thanks!

Chandra

2

Hi

Unfortunately we don’t have any experience with IIS.
However, you can run ShinyProxy on a sub-path by configuring a context-path: Configuration | ShinyProxy

I don’t think ShinyProxy supports the HTTP_X_FORWARDED_PREFIX header, but it should work with just the context-path setting.