gistfile1.rb

class MemcachedPageCaching
  CACHE_HEADER = "X-Cache".freeze
  IGNORED_HEADERS = ['Connection', 'Keep-Alive', 'Proxy-Authenticate', 'Proxy-Authorization', 'TE', 'Trailers', 'Transfer-Encoding', 'Upgrade', 'Set-Cookie'].freeze

  def initialize(app, *addresses)
    @app    = app
    @cache  = Rails.cache
    @logger = Rails.logger

    @logger.info "Initialized MemcachePagecache middleware"

    freeze
  end

  def call(env)
    req = Rack::Request.new(env)
    req_path = ActionController::Base.relative_url_root + req.path_info
    
    if resp = @cache.read(req_path)
      @logger.debug "Serving #{req.fullpath} from memcached"
      resp
    else
      status, headers, body = @app.call(env)

      if status == 200 && headers.include?(CACHE_HEADER)

        headers.delete(CACHE_HEADER)
        headers.keys.each { |h| headers.delete(h) if IGNORED_HEADERS.include?(h) }

        buffer = ""
        body.each { |part| buffer << part }

        resp = [status, headers, buffer]
        @cache.write(req_path, resp)
        resp
      else
        [status, headers, body]
      end
    end
  end
end