Manage Apache Resources Limits With mod_slotlimit

mod_slotlimit is an Apache module that using dynamic slot allocation algorithm and static rules, can manage resources used for each running site.

Preparing Your system

In order to compile mod_slotlimit, you will need to have apxs2 (APache eXtension tool) installed and configured with Apache.

Use the following command to install

#apt-get install apache2-prefork-dev build-essential

Now we download the source package from here


Next open archive, compile and install module with those commands:

#tar zxvf mod_slotlimit.tar.gz

#cd mod_slotlimit-1.1


#make install

This will complete the installation

Load Module

Now in the main config file add mod_slotlimit module.

#vi /etc/apache2/httpd.conf

LoadModule slotlimit_module   /usr/lib/apache2/modules/

Configuring mod_slotlimit

Usefule Directives and if you want more check mod_slotlimit documentation

AvailableSlotsPercent – Percentage of apache slots available in order to activate dynamic slot allocation algorithm
MaxConnectionsPerSite – Max connections for each running site
LimitSite – Specific site to limit
LimitSiteConnections – Max connections for “LimitSite”
ClientIpLimit – Number of maximum simultaneous connection per IP
ForceVhostName – Force vhost hostname in scoreboard. Useful when vhost hostname do not match site visited, for example if you’re using mod_vhost_alias

Now edit apache2 configuration file

#vi /etc/apache2/apache2.conf

Add the following lines save and exit

<IfModule mod_slotlimit.c>
AvailableSlotsPercent 15
MaxConnectionsPerSite 30
LimitSiteConnections 15
ClientIpLimit 15
ForceVhostName On

Now restart Apache server using the following command

#/etc/init.d/apache2 restart

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