Rails 3.1 asset pipeline: how to deal with requests to expired assets?

Question

Once you've set up an application with the asset pipeline, it might generate an image for you with a URL like this (signature truncated):

http://mysite.com/assets/logo-1b2b3c.png

Then, when you change the asset or update the global asset version, you end up with something like this:

http://mysite.com/assets/logo-2b3c1a.png

Now, some people will still be sending requests to the old asset. Under what I understand to be the default Rails 3.1 deploy, these would just 404. That doesn't seem very friendly. It would be nicer to either 301 to the new asset or just deliver the new asset straight up.

Is there some built-in way to do this, or do I have to implement my own asset missing feature?

Answer 1

I implemented it myself:

Myapp::Application.routes.draw do
  match 'assets/:id.:format' => 'assets#show'
end

class AssetsController < ApplicationController
  def show
    asset_without_digest = "#{params[:id].gsub /-[0-9a-f]{32}$/, ''}.#{params[:format]}"
    new_path = ActionView::Base.new.image_path(asset_without_digest)
    if url_for(params).include? new_path
      head 404
    else
      redirect_to new_path, :status => 301
    end
  end
end