Websites and ActiveSync services hosted in Plesk are loading slowly or fail to load with a 50x error: mod_fcgid: can’t apply process slot for /var/www/cgi-bin/cgi_wrapper/cgi_wrapper

Symptoms

• The following message appears on the domain's Logs page at Plesk > Domains > example.com > Logs or in the domain's error log file /var/www/vhosts/system/example.com/logs/error_log:

  mod_fcgid: can't apply process slot for /var/www/cgi-bin/cgi_wrapper/cgi_wrapper

• Websites are loading very slow or loading continuously and eventually fail with an 50x error in a web-browser:

  500 external Server

  502 Bad Gateway

  503 Service Temporarily Unavailable

  504 Gateway Time-out.

• ActiveSync connections with Microsoft Outlook email client are timing out

Cause

The Apache FcgidMaxProcesses limit (the total number of processes FCGID will start for all users) has been reached.

Resolution

1. Connect to the Plesk server via SSH.

2. Increase the value of FcgidMaxProcesses and FcgidMaxProcessesPerClass:

   2.1. Open the fcgid.conf file in a text editor:

   • on CentOS/RHEL-based distributions:

     # vi /etc/httpd/conf.d/fcgid.conf

   • on Debian/Ubuntu-based distributions:

     # vi /etc/apache2/mods-enabled/fcgid.conf

   2.2. Navigate to the directive FcgidMaxProcesses and increase its value. General recommendations: RAM 8GB - about 150, RAM 16GB - 300

   2.3. Navigate to the directive FcgidMaxProcessesPerClass and increase its value to 10 or 15

   2.4. Save the changes and close the file

3. Make sure no other files in the Apache configuration directory override the parameters in fcgid.conf using this command:

   • on CentOS/RHEL-based distributions:

     # grep -irE 'FcgidMaxProcesses|FcgidMaxProcessesPerClass' /etc/httpd/conf.d/

   • on Debian/Ubuntu-based distributions:

     # grep -irE 'FcgidMaxProcesses|FcgidMaxProcessesPerClass' /etc/apache2/

     If files other than fcgid.conf are found, increase the FcgidMaxProcesses and FcgidMaxProcessesPerClass limit in these files too.

4. Restart Apache to apply the changes:

   • on CentOS/RHEL-based distributions:

     # service httpd restart

   • on Debian/Ubuntu-based distributions:

     # service apache2 restart