8.2 Configuration

First, make a directory for mod_perl programs. This directory can be anywhere , except that it's a bad idea to put it in the Apache document tree starting with /var/www/html for the same reasons that it is a bad idea to do so for CGI programs. Let's choose /var/www/mod_perl . Create the directory with the appropriate permissions:

 #  mkdir /var/www/mod_perl  #  chmod a+rx /var/www/mod_perl  

Apache needs to be configured appropriately to use mod_perl effectively. We start by creating a Perl script that Apache runs each time it starts up (or more precisely, each time the Apache configuration file is reread). Name this program startup.pl , since it runs when Apache starts up, and put it in the Apache configuration directory /etc/httpd/conf :

 #! /usr/bin/perl  # tell Perl where to find our modules  use lib /var/www/mod_perl;  # use some common modules  use Apache::Registry();  use Apache::Constants();  use CGI :standard;  use DBI;  # add other modules here...  # the file needs to end with 1;  1; 

The use lib statement tells Apache (really Perl that is built into Apache) where to find the mod_perl modules that we will write ”in this case, the newly minted /var/www/mod_perl directory.

The next four use statements preload four commonly used Perl modules. Preloading at server start-up speeds up loading the individual modules when they are used in the mod_perl programs ^[1] ”if this start-up script weren't used, the modules would have to be loaded the first time each mod_perl program executed, while the client waited for a response from the server.

^[1] As you go along, add any other commonly used modules as needed.

The last line must be 1; ” strange , but important. This program, and all Perl modules, must end in 1; so that when they are used via the use pragma ( use CGI; ), the use must evaluate to 1 (true). To accomplish that, simply make the last line of the module 1; . This needs to be done for all the mod_perl modules.

Then configure Apache to execute the start-up script by adding these lines at the end of the Apache configuration file /etc/httpd/conf/httpd. conf :

 PerlRequire conf/startup.pl  PerlFreshRestart On 

Restart Apache to test the start-up script:

 #  /etc/init.d/httpd graceful  

and check the log file for error messages:

 #  tail -f /var/log/httpd/error_log  

If you see no errors, all is well with the start-up script.