We discovered a bug in Nginx that causes the Nginx service to crash whenever a subdomain is created improperly. In all of the cases where Nginx crashed and failed to restart, we were able to view the logs and identify the account that caused the crash. Upon inspection of the account, we see that there is a subdomain folder, however, there is no subdomain or addon domain inside of cPanel. Nginx sees this folder as a subdomain and creates a virtual host but crashes since there is no identifier inside of cPanel. We have contacted Nginx and they have released a new version that addresses this bug. We will be applying this update shortly to all servers.
To avoid issues in the future, it’s important to always follow the cPanel wizards whenever creating or modifying accounts. In this case, the proper way to create a subdomain or addon domain is by logging into cPanel and following the wizard in either Subdomain or Addon Domains under the Domains section. This will properly create the folder structures and permissions.