I was trying to make apache 2.2 reject connections if MaxClients was reached, to do this I found the directive ListenBacklog.To test it, I configured apache in the following way:
<IfModule mpm_prefork_module> StartServers 5 MinSpareServers 5 MaxSpareServers 10 MaxClients 10 ListenBacklog 1 MaxRequestsPerChild 0 </IfModule>
I've made a little script in JMeter to test this. The test launchs 50 users in 1 second (it requests a phpinfo page) but none is rejected, they all wait! I don't understand how this directive works... my operating system is Ubuntu.