Static Pages on Rails
When I said that favcol is built on Rails, I wasn't being entirely truthful.
I'm not serving anything on the fly to the public, as it only changes once every 5 minutes, my server is a little overloaded and the algorithms I'm using take a little too long.
Instead, I'm (ab)using Rails page caching with a little twist. In short, instead of deleting the cached page whenever it's out of date, it's replaced with a new version.
This only makes sense if your site has frequently requested pages that update rarely and can take little while to render, and you don't mind waiting a few extra seconds for a non-public-facing request to finish. In the case of favcol, this isn't a problem as it's a computer making the request as part of the 5 minute cronjob:
*/5 * * * * /usr/bin/curl -s http://localhost/cron"
This url is mapped to an action looking something like
def cron
if local_request?
# update the data from flickr
Photo.refresh()
# first grab the data needed for the template
index
# then cache the page
cache_page render_to_string(:action => :index),
:controller => "public",
:action => "index"
# return empty string so cron won't send an email
render :text => ""
else
render :text => "not local request"
end
end
If you use this technique, be aware that immediately after a deployment or code update the cached pages may not exist. Adding a caches_page :index to the controller fixes that problem too.