Knowledge Base

Websites on Plesk server are slow or show error 500 or PHP mail cannot be sent: ap_pass_brigade failed

Symptoms

Websites on Plesk server are slow or not available, sending emails via PHP script fails with:

500 external 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
On Ubuntu/Debian:

# 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 domain

Log in to Plesk.
Go to Domains > example.com > Apache & nginx Settings > Additional Apache directives.
Increase the FcgidMaxRequestsPerProcess parameter value in Additional directives for HTTP and Additional directives for HTTPS fields:

<IfModule mod_fcgid.c>
FcgidMaxRequestsPerProcess 500
</IfModule>

Solution for all domains on the server

Connect to the server via SSH.
Open /etc/httpd/conf.d/fcgid.conf (on RedHat/CentOS/CloudLinux) or /etc/apache2/mods-enabled/fcgid.conf (on Ubuntu/Debian) using "vi";
Increase the value of FcgidMaxRequestsPerProcess parameter, e.g. to 500:

<IfModule mod_fcgid.c>
FcgidMaxRequestsPerProcess 500
</IfModule>
Reload Apache configuration:
- On RedHat/CentOS/CloudLinux:
  
  # systemctl reload httpd
- On Ubuntu/Debian:
  
  # systemctl reload apache2
If it does not help, set FcgidOutputBufferSize 0 in the same configuration file and reload Apache again.