The nginx service fails to start/reload with the following error in the
nginx: [emerg] open() "/var/www/vhosts/system/example.com/logs/proxy_access_ssl_log" failed (24: Too many open files)
Some or all websites are not accessible
Warning is shown in the Tools & Settings > Diagnose & repair:
Checking for nginx ULIMIT value N domains have been found on server. Problem with nginx default limit for open files is possible
NodeJS and Ruby web applications are showing 502 Bad Gateway error when performing some Plesk tasks such as creating domains, subscriptions, changes on Apache or Nginx, etc:
502 Bad Gateway
Web server received an invalid response while acting as a gateway or proxy server.
After installing a new certificate for the domain, the old one is still shown in a web browser, however, the correct certificate is selected at the Domains > example.com > Hosting Settings page.
Nginx's virtual host opens 4 log files for each virtual host with physical hosting:
As a result of this fact, the maximum number of open files is exceeded by the nginx server due to a big number of domains (usually, more than 100).
Warning: Execution of the
websrv_ulimits utility without --no-restart option initiates rebuilding of web configuration files for all domains and can cause significant downtime in case of a big number of hosted websites.
Execute the command during the maintenance time frame.
It is good practice to set open files limit value more than number of domains in Plesk * 16 at least. In example below provided actions how to set limit to 4096:
Connect to the server via SSH
Set open files limit to 4096 for both Apache and Nginx:
# /usr/local/psa/admin/sbin/websrv_ulimits --set 4096 --no-restart
Restart Apache and nginx services at Plesk > Tools & Settings > Services Management to apply changes.
Check that 'Max open files limit' was applied properly, after web services restarting:
# grep 'Max open files' /proc/$(cat /var/run/nginx.pid)/limits
Max open files 4096 4096 file
If the solution above did not help, set the limit using the
# ulimit -n 4096