Rails 4 - Error during failsafe response: undefined method 'authenticate' for nil:NilClass

Question

We have a rails 4 app in production environment, on a webrick server, that crashes regularly and returns a 500 error. The crash seems to come from the following error :

Error during failsafe response: undefined method `authenticate' for nil:NilClass
      /usr/local/rvm/gems/ruby-2.1.2/gems/devise-3.2.2/lib/devise/controllers/helpers.rb:58:in `current_user'

We've checked the helpers.rb file at line 58, and so it comes from a call to wardent.authenticate in the 'current_user' method. So we've imported the gem 'warden' in our Gemfile, but nothing changes.

We also tried to change the webrick server into a 'puma' server, thinking it could come from threads, but nothing changed...

The entire error is the following :

Error during failsafe response: undefined method `authenticate' for nil:NilClass
  /usr/local/rvm/gems/ruby-2.1.2/gems/devise-3.2.2/lib/devise/controllers/helpers.rb:58:in `current_user'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/helpers.rb:53:in `current_user'
  /home/dev/myProject/app/views/shared/_top_menu.html.erb:23:in `_app_views_shared__top_menu_html_erb___3475115451092967008_67265400'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:143:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:161:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:141:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/partial_renderer.rb:306:in `render_partial'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/partial_renderer.rb:279:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `block in instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/partial_renderer.rb:278:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/renderer.rb:47:in `render_partial'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/helpers/rendering_helper.rb:27:in `render'
  /home/dev/myProject/app/views/layouts/application.html.erb:18:in `_app_views_layouts_application_html_erb__2013404122424653986_65265180'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:143:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:161:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:141:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/template_renderer.rb:47:in `render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/template_renderer.rb:17:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/renderer.rb:42:in `render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/renderer.rb:23:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:127:in `_render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/streaming.rb:219:in `_render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:120:in `render_to_body'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rendering.rb:33:in `render_to_body'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/renderers.rb:26:in `render_to_body'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:97:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rendering.rb:16:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/core_ext/benchmark.rb:12:in `ms'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:41:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activerecord-4.0.11/lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:40:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/implicit_render.rb:10:in `default_render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/implicit_render.rb:5:in `send_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/base.rb:189:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rendering.rb:10:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/callbacks.rb:18:in `block in process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/callbacks.rb:403:in `_run__2818342425517875908__process_action__callbacks'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/callbacks.rb:80:in `run_callbacks'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/callbacks.rb:17:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rescue.rb:29:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `block in instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activerecord-4.0.11/lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/base.rb:136:in `process'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:44:in `process'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal.rb:195:in `dispatch'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal.rb:231:in `block in action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:82:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:82:in `dispatch'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:50:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/journey/router.rb:71:in `block in call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/journey/router.rb:59:in `each'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/journey/router.rb:59:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:676:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/show_exceptions.rb:43:in `render_exception'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/show_exceptions.rb:33:in `rescue in call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/rack/logger.rb:38:in `call_app'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/rack/logger.rb:20:in `block in call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/tagged_logging.rb:68:in `block in tagged'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/tagged_logging.rb:26:in `tagged'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/tagged_logging.rb:68:in `tagged'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/rack/logger.rb:20:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/request_id.rb:21:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/methodoverride.rb:21:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/runtime.rb:17:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/static.rb:84:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/sendfile.rb:112:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/engine.rb:511:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/application.rb:97:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/lock.rb:17:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/content_length.rb:14:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/handler/webrick.rb:60:in `service'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'
Error during failsafe response: undefined method `authenticate' for nil:NilClass
  /usr/local/rvm/gems/ruby-2.1.2/gems/devise-3.2.2/lib/devise/controllers/helpers.rb:58:in `current_user'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/helpers.rb:53:in `current_user'
  /home/dev/myProject/app/views/shared/_top_menu.html.erb:23:in `_app_views_shared__top_menu_html_erb___3475115451092967008_68619440'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:143:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:161:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:141:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/partial_renderer.rb:306:in `render_partial'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/partial_renderer.rb:279:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/abstract_renderer.rb:38:in `block in instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `block in instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/abstract_renderer.rb:38:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/partial_renderer.rb:278:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/renderer.rb:47:in `render_partial'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/helpers/rendering_helper.rb:27:in `render'
  /home/dev/myProject/app/views/layouts/application.html.erb:18:in `_app_views_layouts_application_html_erb__2013404122424653986_65265180'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:143:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:161:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/template.rb:141:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/template_renderer.rb:61:in `render_with_layout'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/template_renderer.rb:47:in `render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/template_renderer.rb:17:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/renderer.rb:42:in `render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_view/renderer/renderer.rb:23:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:127:in `_render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/streaming.rb:219:in `_render_template'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:120:in `render_to_body'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rendering.rb:33:in `render_to_body'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/renderers.rb:26:in `render_to_body'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:97:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rendering.rb:16:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:41:in `block (2 levels) in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/core_ext/benchmark.rb:12:in `block in ms'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/benchmark.rb:294:in `realtime'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/core_ext/benchmark.rb:12:in `ms'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:41:in `block in render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:84:in `cleanup_view_runtime'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activerecord-4.0.11/lib/active_record/railties/controller_runtime.rb:25:in `cleanup_view_runtime'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:40:in `render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/implicit_render.rb:10:in `default_render'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/implicit_render.rb:5:in `send_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/base.rb:189:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rendering.rb:10:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/callbacks.rb:18:in `block in process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/callbacks.rb:403:in `_run__2818342425517875908__process_action__callbacks'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/callbacks.rb:80:in `run_callbacks'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/callbacks.rb:17:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rescue.rb:29:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `block in instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/notifications.rb:159:in `instrument'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/instrumentation.rb:30:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/params_wrapper.rb:250:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activerecord-4.0.11/lib/active_record/railties/controller_runtime.rb:18:in `process_action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/base.rb:136:in `process'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/abstract_controller/rendering.rb:44:in `process'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal.rb:195:in `dispatch'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_controller/metal.rb:231:in `block in action'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:82:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:82:in `dispatch'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:50:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/journey/router.rb:71:in `block in call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/journey/router.rb:59:in `each'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/journey/router.rb:59:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/routing/route_set.rb:676:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/show_exceptions.rb:43:in `render_exception'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/show_exceptions.rb:33:in `rescue in call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/rack/logger.rb:38:in `call_app'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/rack/logger.rb:20:in `block in call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/tagged_logging.rb:68:in `block in tagged'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/tagged_logging.rb:26:in `tagged'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/tagged_logging.rb:68:in `tagged'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/rack/logger.rb:20:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/request_id.rb:21:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/methodoverride.rb:21:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/runtime.rb:17:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/activesupport-4.0.11/lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/actionpack-4.0.11/lib/action_dispatch/middleware/static.rb:84:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/sendfile.rb:112:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/engine.rb:511:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/application.rb:97:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/lock.rb:17:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/content_length.rb:14:in `call'
  /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/handler/webrick.rb:60:in `service'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'
[2014-11-07 13:06:52] FATAL SignalException: SIGTERM
    /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:170:in `select'
    /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:170:in `block in start'
    /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:32:in `start'
    /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:160:in `start'
    /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/handler/webrick.rb:14:in `run'
    /usr/local/rvm/gems/ruby-2.1.2/gems/rack-1.5.2/lib/rack/server.rb:264:in `start'
    /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/commands/server.rb:84:in `start'
    /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/commands.rb:76:in `block in <top (required)>'
    /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/commands.rb:71:in `tap'
    /usr/local/rvm/gems/ruby-2.1.2/gems/railties-4.0.11/lib/rails/commands.rb:71:in `<top (required)>'
    bin/rails:4:in `require'
    bin/rails:4:in `<main>'
[2014-11-07 13:06:52] INFO  going to shutdown ...
[2014-11-07 13:06:52] INFO  WEBrick::HTTPServer#start done.
Processing by ErrorsController#internal_server_error as HTML
  Rendered errors/internal_server_error.html.erb within layouts/application (0.3ms)
  Rendered shared/_top_menu.html.erb (1.4ms)
Completed 500 Internal Server Error in 3ms

Does anyone has an idea of where it could come from ?

Update

An other error happens just before the error detailed up in this post, here is the error :

    ActiveRecord::ConnectionTimeoutError (could not obtain a database connection within 5.000 seconds (waited 5.000 seconds)):
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:190:in `block in wait_poll'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:181:in `loop'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:181:in `wait_poll'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:136:in `block in poll'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:146:in `synchronize'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:134:in `poll'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:423:in `acquire_connection'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:356:in `block in checkout'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:355:in `checkout'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:265:in `block in connection'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:264:in `connection'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:546:in `retrieve_connection'
  activerecord (4.0.11) lib/active_record/connection_handling.rb:79:in `retrieve_connection'
  activerecord (4.0.11) lib/active_record/connection_handling.rb:53:in `connection'
  activerecord (4.0.11) lib/active_record/query_cache.rb:51:in `restore_query_cache_settings'
  activerecord (4.0.11) lib/active_record/query_cache.rb:43:in `rescue in call'
  activerecord (4.0.11) lib/active_record/query_cache.rb:32:in `call'
  activerecord (4.0.11) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
  actionpack (4.0.11) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.0.11) lib/active_support/callbacks.rb:373:in `_run__2890043484802466369__call__callbacks'
  activesupport (4.0.11) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.11) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.0.11) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  actionpack (4.0.11) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.0.11) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.0.11) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.0.11) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.0.11) lib/active_support/tagged_logging.rb:68:in `block in tagged'
  activesupport (4.0.11) lib/active_support/tagged_logging.rb:26:in `tagged'
  activesupport (4.0.11) lib/active_support/tagged_logging.rb:68:in `tagged'
  railties (4.0.11) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.0.11) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
  rack (1.5.2) lib/rack/runtime.rb:17:in `call'
  activesupport (4.0.11) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  actionpack (4.0.11) lib/action_dispatch/middleware/static.rb:84:in `call'
  rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
  railties (4.0.11) lib/rails/engine.rb:511:in `call'
  railties (4.0.11) lib/rails/application.rb:97:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  rack (1.5.2) lib/rack/content_length.rb:14:in `call'
  rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:138:in `service'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/httpserver.rb:94:in `run'
  /usr/local/rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/webrick/server.rb:295:in `block in start_thread'

Update 2

I've added the 'puma' gem to the Gemfile to enable the puma multi-threading server, and added the following config/initializers/database_connection.rb :

Rails.application.config.after_initialize do
  ActiveRecord::Base.connection_pool.disconnect!

  ActiveSupport.on_load(:active_record) do
    config = ActiveRecord::Base.configurations[Rails.env] ||
                Rails.application.config.database_configuration[Rails.env]
    config['pool']              = ENV['DB_POOL']      || ENV['MAX_THREADS'] || 5
    ActiveRecord::Base.establish_connection(config)
  end
end

But the error still occurs...

Solution !

We've deployed an Apache Server, with Capistrano and Phusion Passenger. Since this time, everything works well, no problems with Rails, or devise, or anything else. I think the problem was we trusted the default Webrick server to work in a production environment, whereas it's intended to work only for development environments...

Thanks to all for your help and your advises

Answer 1

As a follow-on for people who find this error from Google. If you use Devise, this error will occur when Devise cannot initialize properly. If you watch your logs, you might find another error occurring at boot which is preventing Devise from initializing.

In my case, the root issue was that I had pending migrations.

Answer 2

After having installed an Apache Server + Phusion Passenger + Capistrano, and well configured the all environment for a production deploy, everything seems to work well. (Only a webrick server for a production env was, effectivly, a bad idea... even for a beta version)

Thanks to all who helped us and answered our questions.