504 Gateway Timed Out on Laravel Forge with PHP-FPM

I've had a 504 Gateway Timed Out error for two days on my website hosted on Laravel Forge.

After a lot of investigation and testing, I've deduced that only certain models are causing the problem (such as users or media). Some things work, such as User::find(1) for example, but User::all() (40 entries in the database) doesn't work.

An example of the nginx logs:

2024/01/18 15:31:37 [error] 23247#23247: *1216 upstream timed out (110: Connection timed out) while reading response header from upstream, client: ***.***.***.***, server: *****.com, request: "GET /bibliotheque/images HTTP/1.1", upstream: "fastcgi://unix:/run/php/php8.3-fpm.sock", host: "****.com"

I've tried everything, changing things in the PHP-FPM pool configuration, nginx...

I've run out of ideas...

I tried to

Restart the server
Change max timeout in PHP-FPM
Add prameters in nginx

And nothing works

Solution

In case anyone had the same problem, I'd finally managed to find it.

There was a problem with the $with on models that created infinite loops when the same model was called elsewhere with the ::with... method.

After fixing that, everything worked again :)