Cobra Forum

Question: Websites on PHP-FPM are not available and there is a php-fpm process that consumes 100% CPU on Plesk server


Applicable to:

• Plesk for Linux

Symptoms

• Websites on Plesk using PHP-FPM handler hangs and might consume 100% CPU
• A restart of the PHP-FPM service fixes the issue temporarily
• The following error appears in the PHP-FPM error log (i.e. /var/log/plesk-php72-fpm/error.log):

WARNING: [pool example.com] child 5023 said into stderr: "(5023): Error Cannot kill process 2349: Operation not permitted!"

Cause

This is a PHP-FPM bug #74709.


Resolution

This bug was fixed for several PHP versions shipped with Plesk in Obsidian 18.0.34.
It is recommended to update Plesk to the latest release and switch PHP handlers to 7.4.16 or 8.0.3.

Note: As soon as a new version of 7.3 is released, it will get this fix in Plesk as well.

If the update is not possible for some reason or PHP by OS vendor is required, the following workarounds can be applied:


                              Disable OPCache module for the necessary PHP version:


1.Log in to Plesk.

Note: change the "X.X.X PHP handler" to the correct PHP version.

2.Go to Tools & Settings > PHP Settings > X.X.X PHP application

3.Uncheck the opcache checkbox and press the OK button.


          If OPCache is necessary, switch the domains to another PHP handler, e.g. to FastCGI:


For many domains, it is recommended to manage PHP handlers via a service plan.

For locked subscriptions, changes have to be done per subscription.

All cases are described in the following article:

How to customize PHP settings in Plesk?


                                Forbid calling the "kill_all_lockers" function

Note: OPCache can be reset by the function opcache_reset(). For instance:

# /opt/plesk/php/7.2/bin/php -r "opcache_reset();";