How to tell Rails assets that new public asset file was generated - ruby-on-rails

Question

I have a Rails application that is dynamically creating and compiling assets depending from what domain you are accessing the website (let say different colors, where values of colors are stored in database )
let say for www.hello.example it will generate public/assets/hello-application-52777d36dec6f6e311560156da9da1c2.css so browser source file will point to
layout:
= stylesheet_link_tag 'hello-application'
generated html:
<link href="/assets/hello-application-52777d36dec6f6e311560156da9da1c2.css" media="all" rel="stylesheet" />
If you add www.goodbye.example it will compile public/assets/goodbye-application-52777d36dec6f6e311560156da9da1c2.css so browser source file will point to
layout:
= stylesheet_link_tag 'goodbye-application'
generated html:
<link data-turbolinks-track="true" href="/assets/goodbye-application-52777d36dec6f6e311560156da9da1c2.css" media="all" rel="stylesheet" />
Assets are compiled correctly on the fly without need to restart the server.
Examples above work fine if I restart the server
The thing I cannot figure out is how to tell Rails that new public asset file was generated so that = stylesheet_link_tag 'goodbye-application' will pick it up without the need to restart the production server.
My guess is that it has something to do to tell Rails to reload the public/manifest.json I just cannot figure it out
Rails 4.0.2
Ruby 2.1
Unicorn production server
My functionality is kinda similar to krautcomputing article however he is solwing this problem with "Digested" which is not working for rails 4 (+ it will be deprecated soon)
Update
One dude provided an answer (which he had remove) suggesting I don't need to do this because Unicorn have zero time restart, so I can just restart the unicorn and it will load the new public assets... That's true, I'm doing this this way before I've asked this question. However I'm looking for solution that avoid this. (let say users generate 1000 styles per day)
He also suggested to use Grunt... Well, that's plan B, I'm really wondering if there is a way to do this in Rails-sprockets :)

Answer 1

Why not just roll your own helper method?
def subdomain_application_stylesheet_link_tag(subdomain)
if Rails.env.production?
# This assumes you've precompiled the spreadsheet into the public directory via sprockets
stylesheet_link_tag File.basename(
Dir.glob("#{Rails.root}/public/assets/#{subdomain}-application-*.css").first
)
else
# Logic to development stylesheet selection
end
end

Answer 2

Here is the full solution to manifest reloading issue. As stated in the original post, the new manifest.json that you dynamically generate will not reload unless you fully reload your server (or kill works, etc). Just to reiterate:
If you are dynamically creating assets 'live', along with a manifest
to prevent caching, Sprockets doesn't reload the manifest between
requests.
I needed this manifest reloading capability for development only because I am rolling-my-own asset pipeline with Gulp for a performance boost. Basically, using this solution allows the assets to function exactly how they would in production, while still being able to live-reload them when developing with a new manifest...pretty slick, I hope you find it useful for your production needs.
create the file config/initializers/live-manifest.rb:
require 'sprockets/rails/helper'
module Sprockets
module Rails
module Helper
def asset_digest_path(path, options = {})
# create the new manifest, overriding sprockets' old one
if assets_manifest and manifest = Sprockets::Manifest.new(assets, Dir.glob(File.join(assets_manifest.dir, 'manifest-*.json')).first)
if digest_path = manifest.assets[path]
return digest_path
end
end
if environment = assets_environment
if asset = environment[path]
return asset.digest_path
end
end
end
end
end
end
Also, you're more than welcome to customize the new manifest directory if you desire. Mine is in the same place as the previous, with a different name, as you can see from the Dir.glob method call.