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Writing Apache Modules with Perl and C by Lincoln Stein, Doug MacEachern

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8.3. Configuring Apache with Perl

We've just seen how you can configure Perl modules using the Apache configuration mechanism. Now we turn it around to show you how to configure Apache from within Perl. Instead of configuring Apache by hand (editing a set of configuration files), the Perl API allows you to write a set of Perl statements to dynamically configure Apache at runtime. This gives you limitless flexibility. For example, you can create complex configurations involving hundreds of virtual hosts without manually typing hundreds of <VirtualHost> sections into httpd.conf. Or you can write a master configuration file that will work without modification on any machine in a "server farm." You could even look up configuration information at runtime from a relational database.

The key to Perl-based server configuration is the <Perl> directive. Unlike the other directives defined by mod_perl, this directive is paired to a corresponding </Perl> directive, forming a Perl section.

When Apache hits a Perl section during startup time, it passes everything within the section to mod_perl. mod_perl, in turn, compiles the contents of the section by evaluating it inside the Apache::ReadConfig package. After compilation is finished, mod_perl walks the Apache::ReadConfig symbol table looking for global variables with the same names as Apache's configuration directives. The values of those globals are then fed into Apache's normal configuration mechanism as if they'd been typed directly ...

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