Rails assets host with ssl

When we use simple assets server as

ActionController::Base.asset_host = "http://assets%d.example.com"

, so we have a problem with pages which used ssl and some browsers alert users,that some content is not safe.

So I found in the google next solution:

ActionController::Base.asset_host = Proc.new { |source, request|
    "#{request.protocol}assets%d.example.com" % (source.hash % 4)
}

It is beautiful, because for each image we use only one host, so when you refresh you page, a image always have example host ‘assets1’ in each page, not random host.