Very limited 502 Bad Gateway error in Rails

Question

This is so weird.

One of my clients has been consistently getting 502 Bad Gateway errors (without fail and in every browser), but only on one particular page of my Rails site, she can access the rest of the pages normally. Also, everybody else (including people on the same company network) can access the same page fine. Also, the production.log does not contain any trace of an error, it says the page was rendered 200 OK. What could possibly be causing this???

EDIT: I have double-checked that other Rails errors, such as trying to call up the details of a product id that doesn't exist, result in a 404 error instead.

Answer 1

I found it. This was an error with page headers (session object -> cookie) getting too large. I'm using Facebook authentication and was storing the Facebook user session in the session object. For this one person, her personal information on Facebook was too long, so that she was getting this error while everybody else was fine. I fixed the error by only storing the Facebook ID in the session object.