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Webmail or Websites 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

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Kuzma Ivanov
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Applicable to:

  • Plesk for Linux

Symptoms

  • Webmail or Websites are loading very slow or loading continuously and eventually fail with a 50x error in a web-browser: 500 Internal Server, 502 Bad Gateway, 503 Service Temporarily Unavailable, 504 Gateway Time-out.

  • The following message appears on the domain's Logs page (Plesk > Domains > example.com > Logs) or in the domain's error logfile /var/www/vhosts/system/example.com/logs/error_log directly on the server:

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

  • In some cases, the following error message may appear in domain's proxy_error_log file /var/www/vhosts/system/example.com/logs/proxy_error_log:

    CONFIG_TEXT: [log_config:warn] [pid 30019] (32)Broken pipe: [client 203.0.113.2:51022] AH00646: Error writing to |/opt/psa/admin/sbin/pipelog 7081, referer: http://www.example.com/

Cause

The Apache FcgidMaxProcesses, or FcgidMaxProcessesPerClass limit has been reached.

In rare cases, the issue might appear when a client closed the connection before waiting for the server to respond.

Resolution

If the client closed the connection before receiving a server's response, the issue is on the client side.

To increase FcgidMaxProcesses and FcgidMaxProcessesPerClass:

  1. Connect to the Plesk server via SSH.

  2. Increase the value of FcgidMaxProcesses and FcgidMaxProcessesPerClass:

    2.1. Open the fcgid.conf file in any text editor. In this example we are using the vi 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. Check if there are other files in the Apache configuration directory that can override parameters in fcgid.conf. If files other than fcgid.conf are found, increase the FcgidMaxProcesses and FcgidMaxProcessesPerClass limit in these files too.

    • on CentOS/RHEL-based distributions:

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

    • on Debian/Ubuntu-based distributions:

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

  4. Restart Apache to apply the changes:

    • on CentOS/RHEL-based distributions:

      # service httpd restart

    • on Debian/Ubuntu-based distributions:

      # service apache2 restart

  5. Check websites' status.

    If the solution above did not help, switch faulty domains to nginx with PHP-FPM:

    5.1. In Plesk go to at Domains > example.com > PHP Settings and run PHP as FPM application served by nginx.

    5.2. Go to domain's Apache & nginx Settings:

      • Proxy mode
      • Smart static files processing
      • Serve static files directly by nginx

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Comments

2 comments

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    TechTown GmbH

    did you tested that solution...??

    after the restart of the apache the value changes back to the original value

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  • Avatar
    Artyom Baranov

    @TechTown GmbH

    Hello! I have just tested the solution on my Plesk Onyx (CentOS 7)

    # grep -iR 'FcgidMaxProcesses' /etc/httpd/
    /etc/httpd/conf.d/fcgid.conf: FcgidMaxProcesses 20   <----------------before changing

    # vi /etc/httpd/conf.d/fcgid.conf
    # grep -iR 'FcgidMaxProcesses' /etc/httpd/
    /etc/httpd/conf.d/fcgid.conf: FcgidMaxProcesses 40   <----------------after changing

    # service httpd restart

    # grep -iR 'FcgidMaxProcesses' /etc/httpd/
    /etc/httpd/conf.d/fcgid.conf: FcgidMaxProcesses 40   <----------------after Apache restart

    Please describe a scenario when this setting was changed to original value.

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