Description:

Except for the optimizations and the additional ScriptSock directive noted
below, mod_cgid behaves similarly to mod_cgi. See the mod_cgi summary for
additional details about Apache and CGI.

On certain unix operating systems, forking a process from a multi-threaded
server is a very expensive operation because the new process will replicate
all the threads of the parent process. In order to avoid incurring this
expense on each CGI invocation, mod_cgid creates an external daemon that
is responsible for forking child processes to run CGI scripts. The main
server communicates with this daemon using a unix domain socket.

This module is used by default instead of mod_cgi whenever a multi-threaded
MPM is selected during the compilation process. At the user level, this
module is identical in configuration and operation to mod_cgi. The only
exception is the additional directive ScriptSock which gives the name of
the socket to use for communication with the cgi daemon.