Unable to access website: [pool example.com] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 1 idle, and 49 total children

Daniel Yordanov

Updated August 24, 2025 23:56

Plesk for Linux kb: technical

Applicable to:

Plesk Obsidian running on a Linux-based operating system
Unable to access website the website example.com with 502 Bad Gateway or 503 Service Temporarily Unavailable errors showing in a browser
The following error can be found in the log file for the PHP version that this website is configured to use (for example /var/log/plesk-php74-fpm/error.log):

CONFIG_TEXT: WARNING: [pool example.com] seems busy (you may need to increase pm.start_servers, or pm.min/max_spare_servers), spawning 8 children, there are 0 idle, and 129 total children
The Apache error log for the website /var/www/vhosts/example.com/logs/example.com/error_log contains an error that is similar to the following:

CONFIG_TEXT: AH01067: Failed to read FastCGI header, referer: https://example.com/testpage.php

Some or all values for the PHP FastCGI Process Manager (PHP-FPM) directives below were exceeded by the related website:

Apply one of the solutions below:

Solution I

Log into Plesk.
Go to Domains > example.com > PHP Settings > PHP-FPM settings section.
Change pm from dynamic to ondemand
Press the OK button to apply the change
Note: after applying the steps above, the RAM consumption and load on the server can be increased

Solution II

Log into Plesk.
Go to Domains > example.com > PHP Settings > PHP-FPM settings section.
Increase values for the directives pm.start_servers, pm.min_spare_servers, pm.max_spare_servers and press the OK button to apply the changes