Intermittent trouble with mod_perl, Apache2, AppConfig and Exporter

spatterson has asked for the wisdom of the Perl Monks concerning the following question:

Hi, has anyone used mod_perl with AppConfig or Exporter? I'm having some rather mad intermittent errors.

I've written a DB based photo gallery system, using mod_perl2 and Apache2.
There's a core module 'Gallery.pm', package Gallery which handles database and filesystem access, a frontend module 'Frontend.pm', no set package, which generates the display . These are in a common include directory.

Each site has its own index.pl to decide which subs from Frontend to call (i.e. whether to show an image, a set of search results etc).

I have a couple of intermittent problems

sometimes index.pl can't locate the subroutines Frontend.pm exports (undefined subroutine error)
sometimes index.pl doesn't load the config file, so it can't connect to the right database for the gallery.

Gallery.pm exports all its subs using Exporter, they are only ever called by Frontend.pm

require Exporter;
our @ISA = qw(Exporter);
our @EXPORT = qw/insert_image search exif image_tags all_tags path
login_ok
get_unique_filename check_md5_collision title/;
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Frontend.pm exports its subs using Expoter too, they're only called by index.pl.

require Exporter;
our @ISA = qw(Exporter);
our @EXPORT = qw/try_cookie frame_images entrypage tagpage imagepage
rawthumb login logout/;
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index.pl also uses AppConfig to load a config file containing database connection details, a few paths and page titles etc.

Hopefully this all makes sense, does anyone have any suggestions?

just another cpan module author

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Re: Intermittent trouble with mod_perl, Apache2, AppConfig and Exporter by perrin (Chancellor) on Jun 24, 2008 at 18:59 UTC
The problem is that Frontend.pm is not a real module because it doesn't have a package. Once you use() it in one index.pl, it will never be loaded again in that process. If you had a package declared, it would still call the import(), which is created by Exporter, and you'd get your subs. There's more about this in the mod_perl docs.	[reply]