Fixing "upstream sent too big header while reading response header from upstream" error in Laravel Valet Nginx

If you're getting a weird 502 Bad Gateway error with Laravel Valet and, most probably Drupal, chances are your Nginx error log is screaming:

upstream sent too big header while reading response header from upstream.

This is because such resource hogs as Drupal send too big payloads when running in development (or any? ;) mode, and as a result, Nginx fails.

But we can fix that. And no, you don't have to throw Drupal away (most probably you should, but finish the project for the client first).

A recipe for sanity:

1. Go to ~/.config/valet/Nginx directory and create or edit all.conf file.

2. Add the following contents to it:

   ~/.config/valet/Nginx/all.conf

   proxy_buffer_size   128k;
   proxy_buffers   4 256k;
   proxy_busy_buffers_size   256k;
   fastcgi_buffers 16 16k;
   fastcgi_buffer_size 32k;
   fastcgi_busy_buffers_size 32k;
   

3. Save the all.conf file.

4. Restart valet:

   valet restart
   

And you should be good again! Ha-ha Drupal, eat that, you won't ruin my day this time!