Tuning Nginx to handle big headers

The error message that nginx throws is:

upstream sent too big header while reading response header from upstream

This usually happens when the cookie size grows too much e.g. the cookie contains the auth token which embeds a list of permissions. Depending on the granularity of the permissions, the token size can grow significantly affecting the overall header size.

This can be tested using curl:

curl -s -w \%{size_header} -o /dev/null https://example.com

The default configuration in nginx is something like the following:

proxy_buffers 4 256k;
proxy_buffer_size 128k;
proxy_busy_buffers_size 256k;

If the header size is greater than 128k, then we only need to fix proxy_buffer_size.

Here is the reference article:

https://www.getpagespeed.com/server-setup/nginx/tuning-proxy_buffer_size-in-nginx

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• Tag: networking