Adding response headers to static files

[Andy Shipman]

I'm interested in adding a far-forward expiry header to the Response when Merb (or rather Rack) serves static assets, specifically images. From what I've read it seems that Merb is using Merb::Rack::Static to serve static files:

(from my config.ru)

use Merb::Rack::Static, Merb.dir_for(:public)

This in turn is using ::Rack::File to serve the images:

    def serving

      if size = F.size?(@path)

        body = self

      else

        body = [F.read(@path)]

        size = Utils.bytesize(body.first)

      end

      [200, {

        "Last-Modified"  => F.mtime(@path).httpdate,

        "Content-Type"   => Mime.mime_type(F.extname(@path), 'text/plain'),

        "Content-Length" => size.to_s

      }, body]

    end

Ordinarily, the mtime of a file seems reasonable as a Last-Modified date, but as I'm using Heroku, I do a git push to that server and the mtime gets set to the current push time, not when the image last changed. Also, I'd like to add a Cache-Control header to the response as well and take advantage of the upstream HTTP accelerator that Heroku use, i.e. Varnish.

So, short of monkeypatching the Rack::File module, does anyone know of a way to hook into the serving process and add a header? Or is this something I need to ask the Rack list?

Thanks,

Andy Shipman

[Andy Shipman]

I've read some more and discovered Rack::StaticCache in the rack-contrib github repository[1]. This does exactly what I was looking for and works a treat.

I'd certainly recommend it, should anyone else need to cache static assets.

[1]  http://github.com/rack/rack-contrib/blob/3f42d3afe7323d322567d77cd404fb5bd8d9f1eb/lib/rack/contrib/static_cache.rb

2009/12/10 Andy Shipman <an...@cllearview.com>