Website fails to load with 502/503: (13)Permission denied: AH02454: FCGI: attempt to connect to Unix domain socket failed

Symptoms

• PHP-FPM handler is set in Domains > example.com > PHP Settings for a website and it is not accessible with the following error:

  502 Bad Gateway

  503
   Service Temporarily Unavailable
   The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

• The following error is in /etc/apache2/logs/error_log or in /var/www/vhosts/example.com/logs/error_log:

  (13)Permission denied: AH02454: FCGI: attempt to connect to Unix domain socket /var/www/vhosts/system/example.com/php-fpm.sock (127.0.0.1) failed

• Socket file has incorrect permissions (it should be 0660 ):

  # getfacl /var/www/vhosts/system/example.com/php-fpm.sockgetfacl: Removing leading ‘/’ from absolute path names
  file: var/www/vhosts/system/example.com/php-fpm.sock
  owner: root
  group: psaserv
  user::rw-
  group::—
  other::—

Cause

Extended ACL rules are set for /var/www/vhosts/system/ directory and subdirectories, which overwrite correct permissions.

Resolution

1. Connect to the server via SSH;

2. Disable extended ACL rules for /var/www/vhosts/system/ directory

   # setfacl -Rb /var/www/vhosts/system/

If it did not fix the issue, try changing PHP version for the domain:

1. Log into Plesk;
2. Go to Domains > example.com > PHP Settings.