Could it be possible that the overall number of open files exceeds your allotment? Test it with
# lsof | wc -l
Create a /etc/nginx/ulimit.global_params file and enter
worker_rlimit_nofile 64000;
into it. If the worker_rlimit_nofile entry is present in /etc/nginx/nginx.conf omit this step.
Increase the general maximum file descriptor value:
# vi /etc/sysctl.conf
Add/modify:
fs.file-max = 64000
Edit /etc/security/limits.conf and add:
nginx soft nofile 64000
nginx hard nofile 64000
echo 'NGINX_ULIMIT="-n 64000"' >> /etc/sysconfig/nginx
Edit /usr/lib/systemd/system/nginx.service and add a line in the [Service] section:
LimitNOFILE=64000
In /etc/sysconfig/nginx.systemd add:
LimitNOFILE=64000
Add the line ulimit -n 64000 at the beginning of the /usr/local/psa/admin/sbin/nginx-config script:
#!/usr/bin/env bash
ulimit -n 64000
Reload system daemon:
# systemctl --system daemon-reload
# sysctl -p
Restart sw-cp-server and nginx:
# /etc/init.d/sw-cp-server restart
# /etc/init.d/nginx restart
grep 'Max open files' /proc/$(cat /var/run/nginx.pid)/limits
Max open files 4096 4096 file
source:
https://talk.plesk.com/threads/nginx-24-too-many-open-files.347297
https://support.plesk.com/hc/en-us/articles/213938485-nginx-fails-to-start-reload-on-a-Plesk-server-Too-many-open-files