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

Symptoms

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

  CONFIG_TEXT: 502 Bad Gateway

  CONFIG_TEXT: 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:

  CONFIG_TEXT: (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.sock
  getfacl: 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, change PHP version for the domain:

1. Log into Plesk
2. Go to Domains > example.com > PHP Settings
3. Select other PHP version
4. Press OK