Webmaster in a Nutshell, Second Edition

Chapter 15. Web Server Programming with mod_perl

A common criticism of CGI is that it requires forking extra processes each time a script is executed. If you have only a few hits an hour, or even a few hits a minute, this isn’t a big deal. But for a high-traffic site, lots of CGI scripts repeatedly spawning can have an unfortunate effect on the machine running the web server. The CGI scripts will be slow, the web server will be slow, and other processes on the machine will come to a crawl.

One solution to this problem is mod_perl. mod_perl, written by Doug MacEachern and distributed under CPAN, embeds the Perl interpreter directly into the web server. The effect is that your CGI scripts are precompiled by the server and executed without forking, thus running much more quickly and efficiently. Furthermore, CGI efficiency is only one facet of mod_perl. Since mod_perl is a complete Apache/Perl hybrid, other benefits to mod_perl include:

• Writing server side includes in Perl

• Embedding Perl code into the Apache configuration files

• Writing complete Apache modules in Perl

Design of mod_perl

mod_perl is not a Perl module. It is a module of the Apache server, which is currently the most commonly used web server. With mod_perl, you can use Apache configuration directives not only to process CGI scripts much more efficiently, but also to handle all stages in processing a server request.

mod_perl embeds a copy of the Perl interpreter into the Apache httpd executable, providing complete access ...