503 error: "(2)No such file or directory: AH02454: FCGI: attempt to connect to Unix domain socket"

Symptoms

A site shows a 503 error, and messages similar to the following appear in the Apache error log.

[Wed Aug 02 19:46:55.803974 2023] [proxy:error] [pid 1873122:tid 22758486423296] (2)No such file or directory: AH02454: FCGI: attempt to connect to Unix domain socket /opt/cpanel/ea-php81/root/usr/var/run/php-fpm/e386339682d85144e1bf2e9a84c2b9d2ec4ac930.sock (*:80) failed
[Wed Aug 02 19:46:55.804037 2023] [proxy_fcgi:error] [pid 1873122:tid 22758486423296] [client 203.0.113.2:55837] AH01079: failed to make connection to backend: httpd-UDS

Description

The error occurs when the domain has a corrupt PHP-FPM configuration entry.

Workaround

1. Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
2. Use the php_fpm_config command to rebuild the PHP-FMP configuration.

   /usr/local/cpanel/scripts/php_fpm_config --rebuild

Additional rescources

The php_fpm_config Script