Tracking default route usage with Rollbar

application_controller.rb

class ApplicationController < ActionController::Base
  # ...

  before_filter :check_for_default_route
  
  class DefaultRouteException < Exception
    # Placeholder exception so that we can report request & person data back
    # to rollbar
  end
    
  def check_for_default_route
    ignore_user_agents = %w{bingbot googlebot crawler wget curl spider mj12bot}
    if params[:using_default_route]
      if ignore_user_agents.none? {|s| request.env['HTTP_USER_AGENT'].downcase.include?(s)}
        e = DefaultRouteException.new("Default Route for #{request.path.inspect}")
        Rollbar.report_exception(e, rollbar_request_data, rollbar_person_data)
      end
      params.delete(:using_default_route)
    end
  end

  # ...
end

rollbar.rb

# config/initializers/rollbar.rb
require 'rollbar/rails'

if Rails.env.production?
  Rollbar.configure do |config|
    config.access_token = '...'
    config.exception_level_filters.merge!(
      'ApplicationController::DefaultRouteException' => 'warning'
    )
  end
else
  Rollbar.configure do |config|
    # Disabled in dev & test, but we want to be able to call it
    # from controllers
    config.enabled = false
  end
end

routes.rb

Application.routes.draw do
  # ... all your nice explicit routes ...
  
  match '/:controller(/:action(/:id))', using_default_route: true
  # Hack - above route is the one that's actually caught, below is the one
  # that's used by url_for.
  match '/:controller(/:action(/:id))'
end