The north (amazon) periodically falls, what could be the reason?

Question

PHP

Once a week the server falls off, even access via ssh disappears.
here is what is in the logs

2021/08/09 15:11:01 [crit] 2509#2509: *1499598 open() "/var/lib/nginx/fastcgi/6/32/0000008326" failed (13: Permission denied) while reading upstream, client : **.218.21.**, server: , request: "GET / HTTP/1.1", upstream: " fastcgi://unix:/run/php/php7.4-fpm.sock :", host: "mysite .com"

and here's another one dug up.

Error: Use of undefined constant sDomainShort - assumed 'sDomainShort' (this will throw an Error in a future version of PHP) (#2).

Error in line 128 of file '/var/www/html/admin.mysite.com/lib/cfg.php'.

Script: '/index.php'.

if it matters laravel framework.
php7.4

Answer 1

What's the question? You need to diagnose why the server is crashing.
Since everything is so bad that even SSH falls off - it's not nginx or PHP.

Answer 2

Set monitoring and see the metrics at the time of falling off.