rails_admin working in development but not in production or heroku

Question

I have a very basic Rails 3.1rc6 application with basically only Devise, CanCan and rails_admin on it, and a handful of very simple models.

In development environment rails_admin works fine, I can hit localhost:3000/admin and after logging in with my administrator user I can see all the data and manage it.

But when I deploy to Heroku and try to hit appname.herokuapp.com/admin I get "The page you were looking for doesn't exist. You may have mistyped the address or the page may have moved". This is the tail from Heroku logs:

app[web.1]: 
app[web.1]: 
app[web.1]: Started GET "/admin" for 79.157.xx.xx at 2011-08-24 12:15:52 +0000
app[web.1]: 
app[web.1]: ActionController::RoutingError (No route matches {:controller=>"home"}):
heroku[router]: GET appname.herokuapp.com/admin dyno=web.1 queue=0 wait=0ms service=7ms status=404 bytes=728
app[web.1]:   app/controllers/application_controller.rb:5:in `block in <class:ApplicationController>'
app[web.1]: 
app[web.1]: 
app[web.1]: cache: [GET /admin] miss
app[web.1]:   Processing by RailsAdmin::MainController#index as HTML
app[web.1]: Completed 404 Not Found in 2ms

All other routes (Devise routes basically) work fine.

When running Thin in production (webserver that I use in Heroku) in my local machine I get the same:

$ bundle exec rails server thin -e production
=> Booting Thin
=> Rails 3.1.0.rc6 application starting in production on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
Sprockets::Environment#static_root is deprecated
>> Thin web server (v1.2.11 codename Bat-Shit Crazy)
>> Maximum connections set to 1024
>> Listening on 0.0.0.0:3000, CTRL+C to stop

cache: [GET /admin] miss


Started GET "/admin" for 127.0.0.1 at 2011-08-24 13:49:42 +0200
  Processing by RailsAdmin::MainController#index as HTML
Completed 404 Not Found in 3ms

ActionController::RoutingError (No route matches {:controller=>"home"}):
  app/controllers/application_controller.rb:5:in `block in <class:ApplicationController>'

Rendered /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/actionpack-3.1.0.rc6/lib/action_dispatch/middleware/templates/rescues/routing_error.erb within rescues/layout (0.9ms)

And on the browser

Routing Error

No route matches {:controller=>"home"}

This is my routes.rb

root :to => "home#index"
devise_for :users
resources :users, :only => :show
mount RailsAdmin::Engine => '/admin', :as => 'rails_admin'

initializers/rails_admin.rb

RailsAdmin.config do |config|
  config.authorize_with :cancan
  config.reload_between_requests = false
end

Here the routes on heroku

$ heroku run rake routes
Running rake routes attached to terminal... up, run.8
                    root        /                              {:controller=>"home", :action=>"index"}
        new_user_session GET    /users/sign_in(.:format)       {:action=>"new", :controller=>"devise/sessions"}
            user_session POST   /users/sign_in(.:format)       {:action=>"create", :controller=>"devise/sessions"}
    destroy_user_session GET    /users/sign_out(.:format)      {:action=>"destroy", :controller=>"devise/sessions"}
           user_password POST   /users/password(.:format)      {:action=>"create", :controller=>"devise/passwords"}
       new_user_password GET    /users/password/new(.:format)  {:action=>"new", :controller=>"devise/passwords"}
      edit_user_password GET    /users/password/edit(.:format) {:action=>"edit", :controller=>"devise/passwords"}
                         PUT    /users/password(.:format)      {:action=>"update", :controller=>"devise/passwords"}
cancel_user_registration GET    /users/cancel(.:format)        {:action=>"cancel", :controller=>"devise/registrations"}
       user_registration POST   /users(.:format)               {:action=>"create", :controller=>"devise/registrations"}
   new_user_registration GET    /users/sign_up(.:format)       {:action=>"new", :controller=>"devise/registrations"}
  edit_user_registration GET    /users/edit(.:format)          {:action=>"edit", :controller=>"devise/registrations"}
                         PUT    /users(.:format)               {:action=>"update", :controller=>"devise/registrations"}
                         DELETE /users(.:format)               {:action=>"destroy", :controller=>"devise/registrations"}
                    user GET    /users/:id(.:format)           {:action=>"show", :controller=>"users"}
             rails_admin        /admin                         {:to=>RailsAdmin::Engine}

And finally here local routes... the same!

$ rake routes
                    root        /                              {:controller=>"home", :action=>"index"}
        new_user_session GET    /users/sign_in(.:format)       {:action=>"new", :controller=>"devise/sessions"}
            user_session POST   /users/sign_in(.:format)       {:action=>"create", :controller=>"devise/sessions"}
    destroy_user_session GET    /users/sign_out(.:format)      {:action=>"destroy", :controller=>"devise/sessions"}
           user_password POST   /users/password(.:format)      {:action=>"create", :controller=>"devise/passwords"}
       new_user_password GET    /users/password/new(.:format)  {:action=>"new", :controller=>"devise/passwords"}
      edit_user_password GET    /users/password/edit(.:format) {:action=>"edit", :controller=>"devise/passwords"}
                         PUT    /users/password(.:format)      {:action=>"update", :controller=>"devise/passwords"}
cancel_user_registration GET    /users/cancel(.:format)        {:action=>"cancel", :controller=>"devise/registrations"}
       user_registration POST   /users(.:format)               {:action=>"create", :controller=>"devise/registrations"}
   new_user_registration GET    /users/sign_up(.:format)       {:action=>"new", :controller=>"devise/registrations"}
  edit_user_registration GET    /users/edit(.:format)          {:action=>"edit", :controller=>"devise/registrations"}
                         PUT    /users(.:format)               {:action=>"update", :controller=>"devise/registrations"}
                         DELETE /users(.:format)               {:action=>"destroy", :controller=>"devise/registrations"}
                    user GET    /users/:id(.:format)           {:action=>"show", :controller=>"users"}
             rails_admin        /admin                         {:to=>RailsAdmin::Engine}

Any idea on why the rails_admin routes work in development but not in production and what can I do to fix this?

In case it helps, when I run WEBrick in production it fails with

$ rails s production
Exiting
/home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/activesupport-3.1.0.rc6/lib/active_support/dependencies.rb:237:in `require': no such file to load -- rack/handler/production (LoadError)
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/activesupport-3.1.0.rc6/lib/active_support/dependencies.rb:237:in `block in require'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/activesupport-3.1.0.rc6/lib/active_support/dependencies.rb:223:in `block in load_dependency'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/activesupport-3.1.0.rc6/lib/active_support/dependencies.rb:636:in `new_constants_in'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/activesupport-3.1.0.rc6/lib/active_support/dependencies.rb:223:in `load_dependency'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/activesupport-3.1.0.rc6/lib/active_support/dependencies.rb:237:in `require'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/rack-1.3.2/lib/rack/handler.rb:63:in `try_require'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/rack-1.3.2/lib/rack/handler.rb:16:in `get'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/rack-1.3.2/lib/rack/server.rb:269:in `server'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/railties-3.1.0.rc6/lib/rails/commands/server.rb:59:in `start'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/railties-3.1.0.rc6/lib/rails/commands.rb:54:in `block in <top (required)>'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/railties-3.1.0.rc6/lib/rails/commands.rb:49:in `tap'
    from /home/mccoy/.rvm/gems/ruby-1.9.2-p290@talleres-r31/gems/railties-3.1.0.rc6/lib/rails/commands.rb:49:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

But I think this is more of a gem / config problem on my side than anything related. Works fine with development environment though.

Answer 1

After further (and very painful) investigation, I discovered this was caused by cancan and not rails_admin.

The test user in the production database didn't have the right role assigned, so it was not authorized to access rails_admin. This threw the corresponding AccessDenied exception which was handled in application_controller.rb by

rescue_from CanCan::AccessDenied do |exception|
    redirect_to root_url, :alert => exception.message
end

But for some reason redirect_to root_url fails with the aforementioned routing error. Seems I'm not the only one with this problem, after reading this open issue https://github.com/ryanb/cancan/issues/443

The test user in the development database had the right role and could access rails_admin correctly, which made debugging this incredibly frustrating.

At least now I'm in the right path!