PHP-FPM 503 errors on websites that do not have PHP-FPM enabled from WHM or cPanel

Symptoms

You may find that a website is producing "503 Service Unavailable" errors when you visit your browser and the Apache error log, /etc/apache2/logs/error_log, shows entries similar to the following.

[Wed Mar 31 03:19:07.111327 2021] [proxy_fcgi:error] [pid 17628] [client xxx.xxx.xxx.xxx:0] AH01079: failed to make connection to backend: httpd-UDS

When checking in WHM at "Home » Software » MultiPHP Manager," the domain that is having the problem shows that PHP FPM is disabled or unavailable for the domain. 

Description 

If PHP FPM was disabled incorrectly, or a problem occurred on the server that left cruft PHP FPM configuration files in place when they should not be there, it could cause this problem to occur.

Resolution

1. Login to the server via SSH or "Terminal" as the 'root' user.
2. Run the following command to verify that one or more cruft files exist.

   /usr/local/cpanel/scripts/php_fpm_config --check

3. If that command shows a list of cruft files at the end, you must either delete or move the files to a different location on the server.
   Please note, it is recommended to move the files out of the way so that you may examine or restore the files later if needed.
4. Run the following command to rebuild the FPM configuration and restart Apache.

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

5. Visit your domain to confirm that the 503 error has been resolved