cas_devise single sign out doesn't work - ruby-on-rails

Question

Building a CAS client in rails 3.2, I use the gem devise with the extension devise_cas.
Everything works fine login/logout.
BUT When I try to logout directly on the cas server, using the single_sign_out system everything breaks and I have no idea how to solve my problem since it seems to me that it come from the gem I use...
Here is what I get in my logs when the cas server try to inform me about the sign out:
started POST "/UserCasAuth/service" for XX.XX.XX.XX at 2013-07-23 15:08:47 +0000
Processing by Devise::CasSessionsController#single_sign_out as HTML
Parameters: {"logoutRequest"=>"<samlp:LogoutRequest xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\" ID=\"LR-47-trNqu3YBrJMM7CjeUiySDrsXAe1IrxFse1T\" Version=\"2.0\" IssueInstant=\"2013-07-23T16:58:18Z\"><saml:NameID xmlns:saml=\"urn:oasis:names:tc:SAML:2.0:assertion\">#NOT_USED#</saml:NameID><samlp:SessionIndex>ST-55-cZPVpgtFwi5ZR5ozc52r-cas</samlp:SessionIndex></samlp:LogoutRequest>"}
Completed 500 Internal Server Error in 2ms
NoMethodError (undefined method `name' for #<ActionDispatch::Session::CookieStore:0x00000005098828>):
devise_cas_authenticatable (1.3.0) lib/devise_cas_authenticatable/single_sign_out.rb:50:in `destroy_session_by_id'
devise_cas_authenticatable (1.3.0) app/controllers/devise/cas_sessions_controller.rb:66:in `destroy_cas_session'
devise_cas_authenticatable (1.3.0) app/controllers/devise/cas_sessions_controller.rb:39:in `single_sign_out'
actionpack (3.2.12) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (3.2.12) lib/abstract_controller/base.rb:167:in `process_action'
actionpack (3.2.12) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (3.2.12) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (3.2.12) lib/active_support/callbacks.rb:425:in `_run__3173126488054142023__process_action__3586998270345349714__callbacks'
activesupport (3.2.12) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.12) lib/active_support/callbacks.rb:385:in `_run_process_action_callbacks'
activesupport (3.2.12) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.12) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (3.2.12) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (3.2.12) lib/action_controller/metal/instrumentation.rb:30:in `block in process_action'
activesupport (3.2.12) lib/active_support/notifications.rb:123:in `block in instrument'
activesupport (3.2.12) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (3.2.12) lib/active_support/notifications.rb:123:in `instrument'
actionpack (3.2.12) lib/action_controller/metal/instrumentation.rb:29:in `process_action'
actionpack (3.2.12) lib/action_controller/metal/params_wrapper.rb:207:in `process_action'
actionpack (3.2.12) lib/abstract_controller/base.rb:121:in `process'
actionpack (3.2.12) lib/abstract_controller/rendering.rb:45:in `process'
actionpack (3.2.12) lib/action_controller/metal.rb:203:in `dispatch'
actionpack (3.2.12) lib/action_controller/metal/rack_delegation.rb:14:in `dispatch'
actionpack (3.2.12) lib/action_controller/metal.rb:246:in `block in action'
actionpack (3.2.12) lib/action_dispatch/routing/route_set.rb:73:in `call'
actionpack (3.2.12) lib/action_dispatch/routing/route_set.rb:73:in `dispatch'
actionpack (3.2.12) lib/action_dispatch/routing/route_set.rb:36:in `call'
actionpack (3.2.12) lib/action_dispatch/routing/mapper.rb:42:in `call'
journey (1.0.4) lib/journey/router.rb:68:in `block in call'
journey (1.0.4) lib/journey/router.rb:56:in `each'
journey (1.0.4) lib/journey/router.rb:56:in `call'
actionpack (3.2.12) lib/action_dispatch/routing/route_set.rb:601:in `call'
mongoid (3.1.2) lib/rack/mongoid/middleware/identity_map.rb:34:in `block in call'
mongoid (3.1.2) lib/mongoid/unit_of_work.rb:39:in `unit_of_work'
mongoid (3.1.2) lib/rack/mongoid/middleware/identity_map.rb:34:in `call'
devise_cas_authenticatable (1.3.0) lib/devise_cas_authenticatable/single_sign_out/rack.rb:11:in `call'
warden (1.2.1) lib/warden/manager.rb:35:in `block in call'
warden (1.2.1) lib/warden/manager.rb:34:in `catch'
warden (1.2.1) lib/warden/manager.rb:34:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
rack (1.4.5) lib/rack/etag.rb:23:in `call'
rack (1.4.5) lib/rack/conditionalget.rb:35:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/head.rb:14:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/params_parser.rb:21:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/flash.rb:242:in `call'
rack (1.4.5) lib/rack/session/abstract/id.rb:210:in `context'
rack (1.4.5) lib/rack/session/abstract/id.rb:205:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/cookies.rb:341:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
activesupport (3.2.12) lib/active_support/callbacks.rb:405:in `_run__4068638674135561468__call__4242089574650609487__callbacks'
activesupport (3.2.12) lib/active_support/callbacks.rb:405:in `__run_callback'
activesupport (3.2.12) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
activesupport (3.2.12) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (3.2.12) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
rack (1.4.5) lib/rack/sendfile.rb:102:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
railties (3.2.12) lib/rails/rack/logger.rb:32:in `call_app'
railties (3.2.12) lib/rails/rack/logger.rb:16:in `block in call'
activesupport (3.2.12) lib/active_support/tagged_logging.rb:22:in `tagged'
railties (3.2.12) lib/rails/rack/logger.rb:16:in `call'
actionpack (3.2.12) lib/action_dispatch/middleware/request_id.rb:22:in `call'
rack (1.4.5) lib/rack/methodoverride.rb:21:in `call'
rack (1.4.5) lib/rack/runtime.rb:17:in `call'
activesupport (3.2.12) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
rack (1.4.5) lib/rack/lock.rb:15:in `call'
rack-cache (1.2) lib/rack/cache/context.rb:136:in `forward'
rack-cache (1.2) lib/rack/cache/context.rb:143:in `pass'
rack-cache (1.2) lib/rack/cache/context.rb:155:in `invalidate'
rack-cache (1.2) lib/rack/cache/context.rb:71:in `call!'
rack-cache (1.2) lib/rack/cache/context.rb:51:in `call'
railties (3.2.12) lib/rails/engine.rb:479:in `call'
railties (3.2.12) lib/rails/application.rb:223:in `call'
railties (3.2.12) lib/rails/railtie/configurable.rb:30:in `method_missing'
unicorn (4.6.2) lib/unicorn/http_server.rb:552:in `process_client'
unicorn (4.6.2) lib/unicorn/http_server.rb:632:in `worker_loop'
unicorn (4.6.2) lib/unicorn/http_server.rb:500:in `spawn_missing_workers'
unicorn (4.6.2) lib/unicorn/http_server.rb:142:in `start'
unicorn (4.6.2) bin/unicorn_rails:209:in `<top (required)>'
/usr/local/bin/unicorn_rails:19:in `load'
/usr/local/bin/unicorn_rails:19:in `<main>'
EDIT
So I understand the problem come from this file at line 50.
I believe none of the session managers are recognized.
I have indeed removed ActiveRecord since i'm using mongoid, as mentioned in the installation doc. So should I install another session manager or something?
Devise can still its work without it (until the single-sign-out), so I believe it shouldn't be an issue?

Answer 1

Ok So the solution is the following:
As I can understand from this answer on gitHub, I am using the coockieStore to store my session, which is not supported by single sign-out.
So I would need to
use the ActiveRecord session store or some other database-persistent session store
I will update my answer when I will have find out what to do from here.
EDIT
So the solution was to use redis as session store. see redis-store and redis-rails gems.