Who is this for
This article is for those who want an introduction to mod_perl handlers
IntroductionFor a discussion on what mod_perl is and installation requirements is available from a previous article.
What you need to know
You need to know something about Apache configuration. You also need to know something about how Perl uses modules.
Handlers
When
the Apache server gets a request, the request goes through several
stages before a response is send back. Apache has defined these stages
and allowed administrators to define which specfic stages they want to
control. When Apache sees that a specific stage has to be controlled
further, it gives control to the program defined to execute at that
stage.
In mod_perl, these programs are called handlers and are written in Perl.
When
using handlers, you will normally use Perl modules. To improve
efficiency, these modules can be pre-loaded when Apache starts. You can
do this in two ways:
Specify PerlModule in the configuration file
Use
a start-up script. The start-up script is executed at Apache startup.
Aside from pre-loading the modules, you can also perform some other
initiation routines. The start up script has to be defined in the
configuration. You do this by using the PerlRequire directive in the configuration.
Pre-Loading Modules using PerlModule
As we mentioned, modules can be preloaded using the PerlModule directive. If you want to pre-load the Apache::DBI module, you do this in the configuration file:
This tells Apache to pre-load the Apache::DBI module.
Pre-Loading Modules using a Start up Script
To define a start up script, you need to tell Apache that you will require the script. You do this:
PerlRequire "/usr/local/apache2/conf/startup.pl"
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This tells Apache to execute the Perl script at /usr/local/apache2/conf/startup.pl. Your script can then contain use statements to pre-load the modules. You can also add paths for your Perl modules.
use Apache::DBI;
use lib qw(/usr/local/apache2/lib/perl/Concept);
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With
these two statements, you pre-load the Apache::DBI module and also tell
Perl that you have some modules at /usr/local/apache2/lib/perl/Concept.
The
reason why you need to tell Perl where your other modules are, is that
your mod_perl handlers are defined as Perl modules. I prefer to keep my
modules from the standard Perl modules separate so I define a different
directory for my modules. In this case, since these modules are used
within Apache, I define these in the Apache directory.
Where to find more informationTo find more about mod_perl initiation, you can check the mod_perl documentation.
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