IPS4 Problems with Varnish

[Linda A]

First, I know, I know -- everyone here recommends Nginx for front-end caching! That said, we had used Varnish very successfully for several years, and while we're eyeing Nginx, it'll be a few months before things are quiet enough that we can consider the switch.

So, what I'm asking about concerns Varnish, but I'm hoping those with experience with Nginx or other front-end caching solutions might have some ideas about how to fix the issue we're having. Namely, we have gotten people contacting us that our IPS4 forum tells them they are banned (giving message 2s160/4, which from my reading here is probably more a 'Something went wrong message' than 'You are banned message) or that their browser doesn't accept cookies. The latter issue happens more rarely now after some tweaks to rules, but the former is something we've been able to deal with only by creating a special script to allow affected users to set a cookie on themselves that tells Varnish to bypass its system entirely. This is not ideal.

Has anyone using front-end caching come across similar issues? If so, how did you resolve them? I can probably share the VCL rules we have if anyone's interested and thinks it may explain where the problem lies.