You need to have Apache module
mod_status enabled (CentOs main Apache config file is located at /etc/httpd/conf/httpd.conf)
LoadModule status_module modules/mod_status.so
ExtendedStatus on (this is to be set in the same config file as above)
# ExtendedStatus controls whether Apache will generate "full" status
# information (ExtendedStatus On) or just basic information (ExtendedStatus
# Off) when the "server-status" handler is called. The default is Off.
and some access rights set for that (replace below
XXX.XXX.XXX.XXX with your IP - this is to be found in the same config file as above)
# Allow server status reports generated by mod_status,
# with the URL of http://servername/server-status
# Change the ".example.com" to match your domain to enable.
Deny from all
Allow from localhost 127.0.0.1 XXX.XXX.XXX.XXX
Finally you will be seing what each HTTPD process is doing by accessing http://your-server-name/server-status
This will show the pids and URLs currently being processed in the way presented here.