Jeremy Friesen's Programming Blog

Today I spent some time implementing caching in a Rails application that makes use of subdomains.
With a quick bit of google-fu, I stumbled upon Nathaniel Bibler’s post.
A very informative guide, however, the apache rewrite rules proved to be a bit more involved. In addition, the shennagans of the subdomain seemed a little unnecessary, so I opted for host instead of subdomain. The changes are below.

    class ApplicationController < ActionController::Base  
      private
      def cache_page_with_host(content = nil, options = nil)
        path = case options
          when Hash
            url_for(options.merge(:only_path => true, :skip_relative_url_root => true, :format => params[:format]))
          when String
            options
          else
            request.path
        end
        cache_page_without_host(content, File.join("/#{request.host}/", path == "/" ? 'index.html' : path))
      end
    end

Apache Config

RewriteEngine On

# Rewrite rule to check for host cached pages.
# This will check the file system for a cached copy, if that exists
# use the static cached page. 
# The [QSA,L] is very important. See http://httpd.apache.org/docs/2.2/mod/mod_rewrite.html#rewriteflags
RewriteCond %{DOCUMENT_ROOT}/cache/%{HTTP_HOST}/index.html -f
RewriteRule ^/$ /cache/%{HTTP_HOST}/index.html [QSA,L]
RewriteCond %{DOCUMENT_ROOT}/cache/%{HTTP_HOST}/%{REQUEST_URI}.html -f
RewriteRule ^(.*)$ /cache/%{HTTP_HOST}/$1.html [QSA,L]