Allows ActionDispatch errors to be routed within an rails application. Additionally, it can suppress fatal log entries from being written on routing errors.
Include the gem into your Gemfile and update your bundle.
Add e.g.
config.routed_exceptions.non_fatal_routing_errors = true
config.routed_exceptions.in_app_errors = '404'
to your config/application.rb. The first option will disable loging routing errors as fatal errors. The second option allows you to specify which status codes you want to route within your application.
Add e.g.
match '/404', to: 'errors#render_404'
This will route all 404 errors to the render_404 action of your ErrorsController.
To view the effect in development environment as well as in production environment change
config.consider_all_requests_local = false
to
config.consider_all_requests_local = true
Start your application, and visit e.g. http://localhost:3000/somenonexistenturl and the application will serve the action configured in your routes.rb.