Request_uri usually returns the path relative to the root of the application. However, if you try to do redirect_to(request_uri) then you may get unexpected results. This method overwrites request_uri to always include the full front-facing path. This also breaks route recognition, so this is addressed in ActionController::Routing::RouteSet::recognize_path

[Source]

    # File lib/23.rb, line 62
62:                 def request_uri
63:                   uri = old_request_uri
64:                   if ActionController::check_mode_and_base
65:                     uri = BASE_URL + uri unless uri.include?(BASE_URL)
66:                   end
67:                   uri
68:             end