TIL to set X-Forwarded-Proto on requests forwarded from your reverse proxy, otherwise Rack::Session won’t let you set secure cookies. #ruby

— Mike Pastore (@mwpastore) February 15, 2016

If your Rack application (and probably other types of applications) lives behind a reverse proxy, always set an X-Forwarded-Proto request header. I recently ran into an issue where Rack::Session (which I’m using for an OAuth1.0a server-side login flow) wouldn’t let me set a secure cookie because it didn’t think I was serving a secure web site.

I have forwardfor disabled in my HAproxy config because I’m using PROXY protocol to talk to Varnish. Manually adding the X-Forwarded-Proto header to the request fixed the issue, and now I want those three hours of my life back! Hopefully this comes up in someone else’s frantic googling at some point in the future and saves them a similar headache.