Add proper error page for request timeouts

app/controllers/application_controller.rb

@@ -12,6 +12,7 @@ class ApplicationController < ActionController::Base
   rescue_from ActionController::RoutingError, with: :not_found
   rescue_from ActiveRecord::RecordNotFound, with: :not_found
   rescue_from ActionController::InvalidAuthenticityToken, with: :unprocessable_entity
+  rescue_from Rack::Timeout::RequestExpiryError, Rack::Timeout::RequestTimeoutError, with: :request_timeout
 
   before_action :store_current_location, except: :raise_not_found, unless: :devise_controller?
   before_action :set_locale
@@ -69,6 +70,13 @@ class ApplicationController < ActionController::Base
     end
   end
 
+  def request_timeout
+    respond_to do |format|
+      format.any  { head 503 }
+      format.html { render 'errors/503', layout: 'error', status: 503 }
+    end
+  end
+
   def current_account
     @current_account ||= current_user.try(:account)
   end

app/views/errors/503.html.haml

@@ -0,0 +1,5 @@
+- content_for :page_title do
+  Request timeout
+
+- content_for :content do
+  It took too long to process your request. This might be a temporary server issue