Issue Switching from FCGI to PHP-FPM fails

[Peter99]

Server operating system version

AlmaLinux 8.8 (Sapphire Caracal)

Plesk version and microupdate number

Version 18.0.56

Since the last Plesk update, we experience a weird issue.

When we go into a subscriptions PHP extension to change the "Run PHP as" from "FastCGI application Served by Apache" and changes it to "FPM application served by Apache", the website responds with a 503 page.

The website error log is logging this error:
Error (2)No such file or directory: AH02454: FCGI: attempt to connect to Unix domain socket /var/www/vhosts/system/domain/php-fpm.sock (*) failed Apache error
AH01079: failed to make connection to backend: httpd-UDS Apache error

If we then go into Tools and Settings > Services Management and restart the PHP-FPM process, the website is now working and the 503 error is gone.
I have only experienced this, since our upgrade to the latest Plesk version.

 

[Peter Debik]

Unfortunately, PHP-FPM service sometimes can crash. However, that is an issue of that service or conditions on the server. For my personal use I found that it makes sense to restart the plesk-php<version>-fpm services once every two or three weeks by crontab job. It helped to avoid these issues, but that is just a personal experience, it might not apply to your specific server situation.

 

[Peter99]

Unfortunately, PHP-FPM service sometimes can crash. However, that is an issue of that service or conditions on the server. For my personal use I found that it makes sense to restart the plesk-php<version>-fpm services once every two or three weeks by crontab job. It helped to avoid these issues, but that is just a personal experience, it might not apply to your specific server situation.

This should automaticly be covered by the various kernel updates we are doing and as a result rebooting the entire server.

However, this seems to happen no matter what website we change the type of PHP processor on. I can pick another subscription and change the PHP processor and it will fail with 503.
This means that currently every time we change the type of PHP processor, we must remember to head into Services Management and restart the PHP-FPM process.
Funny thing is that it only has begun after we did the upgrade to latest Plesk version.