Today I migrated EveKnows.com from mod_cgi to mod_perl and switched from using Perl to directly output HTML to using the HTML::Template module to handle formatting. The move to HTML::Template has been a long time in coming–I’m a big fan of separating logic from presentation, and this finally allows me to do that with EveKnows. Editing the HTML was getting messy since it was all embedded in the Perl code, and small changes on my staging server were breaking programming logic. Now the search engine is broken up into a Perl back-end and a simple HTML front-end, which should allow me to easily upgrade the interface as the engine matures.
While I was researching HTML::Template, I came across some benchmarks showing the benefits of using Apache’s mod_perl rather than running regular CGI processes, which is how EveKnows was originally designed. Besides cool advantages such as shared memory caching, mod_perl is generally an order of magnitude faster at rendering an HTML file from a Perl source script. EveKnows.com didn’t get *that* much of a performance improvement from the migration (most of its processing time is spent searching and sorting data), but it did increase from being able to serve ~2 requests/second to ~10/second, which is a pretty hefty increase. For anyone attempting a similar migration, I’d like to point out a couple of issues I ran into.
First, Apache needs to be told to use mod_perl rather than mod_cgi. This means editing your httpd.conf file (or virtual host file if you use those) and adding the following section:
SetHandler perl-script
PerlResponseHandler ModPerl::Registry
PerlOptions +ParseHeaders
Options ExecCGI FollowSymLinks
Restart Apache and any scripts ending in .cgi will now be processed by mod_perl.
The second problem stemmed from CGI::Simple. For whatever reason, this module does not play nice with mod_perl. I had to switch to the regular CGI module to get things back to normal.
Anyway, once these fixes were in place, EveKnows.com was working faster and cleaner than ever!
