Issue NGINX [emerg] "fastcgi_cache" zone "*****.it_fastcgi" is unknown in /etc/nginx/nginx.conf:41 nginx: configuration file /etc/nginx/nginx.conf

[Lorenzo P]

Server operating system version

CentOs 7

Plesk version and microupdate number

Version 18.0.45

Hello everybody!
For a few months, the error in the title has appeared on my Plesk homepage. When it first appeared, I immediately checked line 41 of the nginx.conf file to see what the problem could be, but I couldn't find any mention of "fastcgi_cache" anywhere in the file.
I tried using Plesk's web server troubleshooting tool and noticed that many of the hosted domains have configuration errors, but when I look for more details, the error is always the same as what is displayed on the homepage.

I really don't know where to look for the problem and what to do to resolve it, especially since the server in question is in production, and I want to avoid permanently disrupting the Nginx service.

Additionally, do you think this type of error would be critical during an update of Plesk or its components?

Can any of you help me out?

_________________________________________________________

Here is the nginx.conf

[root@ nginx]# cat nginx.conf

#user  nginx;
worker_processes  1;

#error_log  /var/log/nginx/error.log;
#error_log  /var/log/nginx/error.log  notice;
#error_log  /var/log/nginx/error.log  info;

#pid        /var/run/nginx.pid;

include /etc/nginx/modules.conf.d/*.conf;

events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  /var/log/nginx/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;
    #tcp_nodelay        on;

    #gzip  on;
    #gzip_disable "MSIE [1-6]\.(?!.*SV1)";

    server_tokens off;

    include /etc/nginx/conf.d/*.conf;
}

# override global parameters e.g. worker_rlimit_nofile
include /etc/nginx/*global_params;

_______________________________________

And here the nginx.service status:

nginx.service - Startup script for nginx service
   Loaded: loaded (/usr/lib/systemd/system/nginx.service; enabled; vendor preset: disabled)
  Drop-In: /usr/lib/systemd/system/nginx.service.d
           └─limit_nofile.conf, respawn.conf
   Active: active (running) since Fri 2023-10-20 06:32:03 CEST; 10h ago
  Process: 27494 ExecReload=/bin/kill -s HUP $MAINPID (code=exited, status=0/SUCCESS)
  Process: 27479 ExecReload=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS)
  Process: 27465 ExecReload=/bin/sh -c [ '${NGINX_ENABLED}' = 'yes' ] || { echo Not reloading nginx as it is disabled in Plesk. Run \'plesk sbin nginxmng -e\' to enable nginx in Plesk.; exit 1; } (code=exited, status=0/SUCCESS)
  Process: 7995 ExecStart=/usr/sbin/nginx (code=exited, status=0/SUCCESS)
  Process: 6942 ExecStartPre=/usr/sbin/nginx -t (code=exited, status=0/SUCCESS)
  Process: 6851 ExecStartPre=/bin/sh -c [ '${NGINX_ENABLED}' = 'yes' ] || { echo Not starting nginx as it is disabled in Plesk. Run \'plesk sbin nginxmng -e\' to enable nginx in Plesk.; exit 1; } (code=exited, status=0/SUCCESS)
 Main PID: 8358 (nginx)
   CGroup: /system.slice/nginx.service
           ├─ 8358 nginx: master process /usr/sbin/ngin
           ├─27562 Passenger watchdog                                                     
           ├─27566 Passenger core                                                     
           ├─27595 nginx: worker proces
           └─27596 nginx: cache manager proces

Oct 20 09:01:44 plsk******.it systemd[1]: Reloading Startup script for nginx service.
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: [warn] no "fastcgi_cache_key" for "fastcgi_cache" in /etc/nginx/nginx.conf:41
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: [warn] no "fastcgi_cache_key" for "fastcgi_cache" in /etc/nginx/nginx.conf:41
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: [warn] no "fastcgi_cache_key" for "fastcgi_cache" in /etc/nginx/nginx.conf:41
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: [warn] no "fastcgi_cache_key" for "fastcgi_cache" in /etc/nginx/nginx.conf:41
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: [warn] no "fastcgi_cache_key" for "fastcgi_cache" in /etc/nginx/nginx.conf:41
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: [warn] no "fastcgi_cache_key" for "fastcgi_cache" in /etc/nginx/nginx.conf:41
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
Oct 20 09:01:44 plsk******.it nginx[27479]: nginx: configuration file /etc/nginx/nginx.conf test is successful
Oct 20 09:01:45 plsk******.it systemd[1]: Reloaded Startup script for nginx service.