Why did 504 Gateway Timeout start appearing (Perl site)?

Question

Perl

There is one ancient site with a self-written Perl engine. About a month ago, a problem appeared: in the admin panel, it is possible to upload up to 3 images to a product. When loading one, everything goes smoothly, but if you try to load 2-3 files, it gives:

504 Gateway Timeout
The gateway did not receive a timely response from the upstream server or application.
Apache/2.2.22 (Fedora) Server at domain.com Port 80

At the same time, despite the error, the files are still uploaded to the server.
Here is what I see in the logs:

[error] [client x.x.x.x] (70007)The timeout specified has expired: Error reading request entity data, referer: http://domain.com/adm/products.mod?saved=1&id=1176&job=edit_item

And here is a piece of code, after which an error pops up (as it seems to me):

...} elsif ($job eq 'save_item') {
...
# Редиректимся на страницу редактирования
# чтоб 'F5' не вызывал операцию сохранения повторно
http_redirect(AdmURL($mod, id=>$id, job=>'edit_item', saved=>1));
} elseif {...

Tell me which way to dig, given that I only have access to FTP, to the site's admin panel, and to the database.

Answer 1

Look at the logs. Most likely some resource ran out - disk, memory. Maybe the problem is in the changes in the updated DBMS - there are such changes ...
try to see what the AdmURL returns