mod_perl 2.0 is trying hard to be backward compatible with mod_perl 1.0. However, some things (mostly APIs) have changed. To gain complete compatibility with 1.0 while running under 2.0, you should load the compatibility module as early as possible:
at server startup. Unless there are forgotten things or bugs, your code should work without any changes under the 2.0 series.
However, if you don't have a good reason to keep 1.0 compatibility, you should try to remove the compatibility layer and adjust your code to work under 2.0 without it. This will improve performance. The online mod_perl documentation includes a document (http://perl.apache.org/docs/2.0/user/porting/compat.html) that explains what APIs have changed and what new APIs should be used instead.
If you have mod_perl 1.0 and 2.0 installed on the same system and the two use the same Perl libraries directory (e.g., /usr/lib/perl5), to use mod_perl 2.0 make sure to first load the Apache2 module, which will perform the necessary adjustments to @INC:
use Apache2; # if you have 1.0 and 2.0 installed use Apache::compat;
So if before loading Apache2.pm the @INC array consisted of:
/usr/lib/perl5/5.8.0/i686-linux-thread-multi /usr/lib/perl5/5.8.0 /usr/lib/perl5/site_perl/5.8.0/i686-linux-thread-multi /usr/lib/perl5/site_perl/5.8.0 /usr/lib/perl5/site_perl .
it will now look like this:
/usr/lib/perl5/site_perl/5.8.0/i686-linux-thread-multi/Apache2 /usr/lib/perl5/5.8.0/i686-linux-thread-multi /usr/lib/perl5/5.8.0 /usr/lib/perl5/site_perl/5.8.0/i686-linux-thread-multi /usr/lib/perl5/site_perl/5.8.0 /usr/lib/perl5/site_perl .
Notice that a new directory was appended to the search path. If, for example, the code attempts to load Apache::Server and there are two versions of this module under /usr/lib/perl5/site_perl/:
Finally, mod_perl 2.0 has all its methods spread across many modules. To use these methods, you first have to load the modules containing them. The ModPerl::MethodLookup module can be used to figure out what modules need to be loaded. For example, if you try to use:
and mod_perl complains that it can't find the construct_url( ) method, you can ask ModPerl::MethodLookup:
panic% perl -MApache2 -MModPerl::MethodLookup -e print_method construct_url
This will print:
to use method 'construct_url' add: use Apache::URI ( );
Another useful feature provided by ModPerl::MethodLookup is the preload_all_modules( ) function, which preloads all mod_perl 2.0 modules. This is useful when you start to port your mod_perl 1.0 code (though preferrably avoided in the production environment to save memory). You can simply add the following snippet to your startup.pl file:
use ModPerl::MethodLookup; ModPerl::MethodLookup::preload_all_modules( );