We’ve recently moved a couple of Hyperactive sites to run on mod_rails, a recently released Apache module which allows much easier deployment of Rails sites which run on a single box. Using it gives the nice happy glow that you get from using Apache’s PHP module – dump your project code into a directory accessible by Apache and it executes. This contrasts with the more complex process of setting up and maintaining a Mongrel cluster using mod_proxy_balancer (although that option still has a lot to recommend it, especially if you want to run a site across multiple servers in your data centre).
Everything works very well so far, but I did run into one problem. If you’re using full page caching in Rails, mod_rails automatically finds your cache files and tells Apache to render them from disk instead of hitting the Rails stack if a cache for a given URL. However, it only finds the cache files if they’re in the default location (RAILS_ROOT/public). Personally I find the default location a bit messy, since the cache files get mixed in with all the other stuff in your /public directory – so I tend to put cache files at RAILS_ROOT/public/system/cache to keep things clean.
config.action_controller.page_cache_directory = RAILS_ROOT + "/public/system/cache/"The trouble was that mod_rails didn’t pick up these cache files by default, so I went back to Apache rewrite rules. I dumped in my old rewrite rules from my Mongrel configuration, and everything seemed to be working. Cached pages were served statically, due to this rewrite rule:
# Rewrite to check for Rails cached page
RewriteRule ^([^.]+)$ /system/cache/$1.html [QSA]I haven’t seen anyone else report this problem, but I had one bit of trouble. My application obviously uses a POST request rather than a GET request to send an update to the server, but the route is otherwise the same. Attempting to edit a piece of content on the site resulted in Apache intercepting the call and just showing the content again, bypassing the “update” method call and making the site’s content impossible to edit. I have no idea why this is the case with mod_rails but didn’t happen with Mongrel, but whatever – I’ve just added the following rewrite condition to my Apache configuration and it seems to work fine:
# Rewrite to check for Rails cached page
RewriteCond %{THE_REQUEST} !^POST
RewriteRule ^([^.]+)$ /system/cache/$1.html [QSA]This means that Apache won’t attempt to pull the file from the cache for any POST requests (like updates), making it all work again.
