SPUG: Newbie mod_perl q: When modules are loaded

Dan Sanderson spug at dansanderson.com
Fri May 7 23:12:59 CDT 2004

Hi all -

I'm getting started with mod_perl on a toy server I own.  (I have root and
can modify Apache configuration, and can restart the web server.)  It's
running Debian 3.0r2 stable, and I'm keeping it that way, which means I'm
using Apache 1.3.26 and mod_perl 1.26.  I'm starting out with trying to
use Apache::Registry to speed up regular Perl CGI scripts.

I understand that mod_perl compiles and caches scripts and modules once on
first load, and uses the cached versions on subsequent loads.  A default
configuration knows to recompile scripts when they change, but not
modules.  At the cost of performance, the following Apache configuration
line would also check modules for updates before loading the cached
 PerlInitHandler Apache::StatINC

When I tried this, I noticed that my apps (specifically Kwiki) would
complain about missing modules about half the time.  Always, a reload of
the page would succeed.

When I removed the line, most of the original behavior was restored,
except one of the modules is permanently unavailable.  The error says
"Can't locate CGI/Kwiki/Changes.pm in @INC (@INC contains: ...)", where
the paths definitely do not contain the module.  The app normally finds
the module using a "use lib" line to the path to the libraries in the CGI
script, and it does this successfully for other parts of the Kwiki.  The
use lib path is not in the list of paths in the error message.

Kwiki's index.cgi loads modules by name from its configuration file:
changes_class is set to "CGI::Kwiki::Changes".  Would this cause a
specific problem for mod_perl, with or without the StatINC configuration?

Given that mod_perl doesn't reload modules with a high performance
configuration, what's the best way to refresh the cache when new modules
are deployed (presumably from a test instance to a production instance)?

Is there a better way to configure a development instance of a mod_perl
website to reload modules when they change, than StatINC?  The docs
tentatively suggest a couple of other options, but I get the impression
there is no official recommendation.  Is that about right?

Is mod_perl 2 better at this?

Thanks for any advice you can provide!

-- Dan

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