How to avoid nginx "upstream sent too big header" errors?

Question

I'm running nginx, Phusion Passenger and Rails.

I am running up against the following error:

upstream sent too big header while reading response header from upstream, client: 87.194.2.18, server: xyz.com, request: "POST /user_session HTTP/1.1", upstream: "passenger://unix:/tmp/passenger.3322/master/helper_server.sock

It is occuring on the callback from an authentication call to Facebook Connect.

After googling, and trying to change nginx settings including proxy_buffer_size and large_client_header_buffers is having no effect.

How can I debug this?

Answer 1

Try to add this to the config:

http {
    ...
    proxy_buffers 8 16k;
    proxy_buffer_size 32k;
    }