How do I fix Nginx 502 Bad Gateway on large headers?

Question

I have a Django REST Framework app running behind an Nginx proxy, we have a third party service that redirects to one of the urls in the app. I'm getting 502s from this endpoint when the redirect happens and have narrowed it down to the Referer header being too large. My logic is as follows:

• Received 502 when the redirect happens
• Hitting the link locally with all the query params returns the expected response
• Adding the Referer header (which is quite large) triggers the 502
• Removing half of the Referer header returns us to the expected result

I've tried increasing my uwsgi buffer-size and nginx proxy buffer.

Answer 1

After a number of hours trying out different things, the reason was in fact the uwsgi buffer-size just not being high enough even though I had quadrupled it. For those that don't know, you need to add:

buffer-size=32768

Where the number is some number of bytes that works for your use case. The default is 4096.