Question: Websites on Plesk server are slow or show error 500 or PHP mail cannot be sent: ap_pass_brigade failed
Applicable to:Symptoms- Websites on Plesk server are slow or not available, sending emails via PHP script fails with:
500 Internal server error
- Domains > exemple.com > Logs or /var/www/vhosts/example.com/logs/error_log show:
mod_fcgid: ap_pass_brigade failed in handle_request_ipc function, referer: http://www.example.com/index.php
Cause
The connection is being reset due to the FcgidMaxRequestsPerProcess limit has been reached. The parameter was previously defined in the web configuration:
- On RedHat/CentOS/CloudLinux:
# grep FcgidMaxRequestsPerProcess /etc/httpd/conf.d/fcgid.conf /var/www/vhosts/system/example.com/conf/vhost.conf /var/www/vhosts/system/example.com/conf/httpd.conf
# grep FcgidMaxRequestsPerProcess /etc/apache2/mods-enabled/fcgid.conf /var/www/vhosts/system/example.com/conf/vhost.conf /var/www/vhosts/system/example.com/conf/httpd.conf
Resolution Solution for one particular domain1.Log in to Plesk.
2.Go to Domains > example.com > Apache & nginx Settings > Additional Apache directives.
3.Increase the FcgidMaxRequestsPerProcess parameter value in Additional directives for HTTP and Additional directives for HTTPS fields:
<IfModule mod_fcgid.c>
FcgidMaxRequestsPerProcess 500
</IfModule>(https://pix.cobrasoft.org/images/2025/11/29/mceclip0-11.png)
Solution for all domains on the server1.Connect to the server via SSH.
2.Open /etc/httpd/conf.d/fcgid.conf (on RedHat/CentOS/CloudLinux) or /etc/apache2/mods-enabled/fcgid.conf (on Ubuntu/Debian) using "vi";
3.Increase the value of FcgidMaxRequestsPerProcess parameter, e.g. to 500:
<IfModule mod_fcgid.c>
FcgidMaxRequestsPerProcess 500
</IfModule>
4.Reload Apache configuration:
- On RedHat/CentOS/CloudLinux:
# systemctl reload httpd
# systemctl reload apache2
5.If it does not help, set FcgidOutputBufferSize 0 in the same configuration file and reload Apache again.