undefined method `extend' for class `ActiveRecord::Associations::CollectionProxy'

[Codrut Gusoi]

I have a rails 3.2.21 app hosted on Heroku, using Heroku Postgres. I got the "undefined method `extend' for class `ActiveRecord::Associations::CollectionProxy'" error fired from every page on one of the web dynos. After a while the dyno was restarted and everything went back to normal. 

I have no idea what could cause such an error, any hint would be great.  

In case you need, here is a stack trace from one of the pages:

….21/lib/active_record/associations/

collection_proxy.rb:  37:in `<class:CollectionProxy>'
….21/lib/active_record/associations/

collection_proxy.rb:  36:in `<module:Associations>'
….21/lib/active_record/associations/

collection_proxy.rb:   2:in `<module:ActiveRecord>'
….21/lib/active_record/associations/

collection_proxy.rb:   1:in `<top (required)>'
…b/active_record/associations/

collection_association.rb:  25:in `initialize'
…ve_record/associations/

has_many_through_association.rb:  10:in `initialize'
…/activerecord-3.2.21/lib/active_record/

associations.rb: 160:in `new'
…/activerecord-3.2.21/lib/active_record/

associations.rb: 160:in `association'
…ib/active_record/associations/preloader/

association.rb:  18:in `run'
…ord-3.2.21/lib/active_record/associations/

preloader.rb: 132:in `block (2 levels) in preload_one'
…ord-3.2.21/lib/active_record/associations/

preloader.rb: 131:in `each'
…ord-3.2.21/lib/active_record/associations/

preloader.rb: 131:in `block in preload_one'
…ord-3.2.21/lib/active_record/associations/

preloader.rb: 130:in `each'
…ord-3.2.21/lib/active_record/associations/

preloader.rb: 130:in `preload_one'
…ord-3.2.21/lib/active_record/associations/

preloader.rb: 109:in `preload'
…/squeel/adapters/active_record/

preloader_extensions.rb:  14:in `block in run_with_squeel'
…/squeel/adapters/active_record/

preloader_extensions.rb:  14:in `each'
…/squeel/adapters/active_record/

preloader_extensions.rb:  14:in `run_with_squeel'
…gems/activerecord-3.2.21/lib/active_record/

relation.rb: 181:in `block in exec_queries'
…gems/activerecord-3.2.21/lib/active_record/

relation.rb: 180:in `each'
…gems/activerecord-3.2.21/lib/active_record/

relation.rb: 180:in `exec_queries'
…gems/activerecord-3.2.21/lib/active_record/

relation.rb: 160:in `block in to_a'
…/gems/activerecord-3.2.21/lib/active_record/

explain.rb:  41:in `logging_query_plan'
…gems/activerecord-3.2.21/lib/active_record/

relation.rb: 159:in `to_a'
…rd-3.2.21/lib/active_record/relation/

finder_methods.rb: 381:in `find_first'
…rd-3.2.21/lib/active_record/relation/

finder_methods.rb: 122:in `first'
….1.0/gems/friendly_id-4.0.9/lib/friendly_id/

history.rb:  92:in `find_one'
…rd-3.2.21/lib/active_record/relation/

finder_methods.rb: 315:in `find_with_ids'
…rd-3.2.21/lib/active_record/relation/

finder_methods.rb: 107:in `find'
            /app/app/controllers/

programs_controller.rb:   8:in `show'
…-3.2.21/lib/action_controller/metal/

implicit_render.rb:   4:in `send_action'
…gems/actionpack-3.2.21/lib/abstract_controller/

base.rb: 167:in `process_action'
…onpack-3.2.21/lib/action_controller/metal/

rendering.rb:  10:in `process_action'
…actionpack-3.2.21/lib/abstract_controller/

callbacks.rb:  18:in `block in process_action'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb: 458:in `_run__283287050225388972__process_action__1943163135672811662__callbacks'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb: 405:in `__run_callback'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb: 385:in `_run_process_action_callbacks'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb:  81:in `run_callbacks'
…actionpack-3.2.21/lib/abstract_controller/

callbacks.rb:  17:in `process_action'
…ctionpack-3.2.21/lib/action_controller/metal/

rescue.rb:  29:in `process_action'
…-3.2.21/lib/action_controller/metal/

instrumentation.rb:  30:in `block in process_action'
…tivesupport-3.2.21/lib/active_support/

notifications.rb: 123:in `block in instrument'
….2.21/lib/active_support/notifications/

instrumenter.rb:  20:in `instrument'
…tivesupport-3.2.21/lib/active_support/

notifications.rb: 123:in `instrument'
…-3.2.21/lib/action_controller/metal/

instrumentation.rb:  29:in `process_action'
…k-3.2.21/lib/action_controller/metal/

params_wrapper.rb: 207:in `process_action'
….2.21/lib/active_record/railties/

controller_runtime.rb:  18:in `process_action'
…gems/actionpack-3.2.21/lib/abstract_controller/

base.rb: 121:in `process'
…actionpack-3.2.21/lib/abstract_controller/

rendering.rb:  45:in `process'
…/gems/actionpack-3.2.21/lib/action_controller/

metal.rb: 203:in `dispatch'
…-3.2.21/lib/action_controller/metal/

rack_delegation.rb:  14:in `dispatch'
…/gems/actionpack-3.2.21/lib/action_controller/

metal.rb: 246:in `block in action'
…onpack-3.2.21/lib/action_dispatch/routing/

route_set.rb:  73:in `call'
…onpack-3.2.21/lib/action_dispatch/routing/

route_set.rb:  73:in `dispatch'
…onpack-3.2.21/lib/action_dispatch/routing/

route_set.rb:  36:in `call'
…le/ruby/2.1.0/gems/journey-1.0.4/lib/journey/

router.rb:  68:in `block in call'
…le/ruby/2.1.0/gems/journey-1.0.4/lib/journey/

router.rb:  56:in `each'
…le/ruby/2.1.0/gems/journey-1.0.4/lib/journey/

router.rb:  56:in `call'
…onpack-3.2.21/lib/action_dispatch/routing/

route_set.rb: 608:in `call'
…uby/2.1.0/gems/omniauth-1.0.3/lib/omniauth/

strategy.rb: 168:in `call!'
…uby/2.1.0/gems/omniauth-1.0.3/lib/omniauth/

strategy.rb: 148:in `call'
…uby/2.1.0/gems/omniauth-1.0.3/lib/omniauth/

strategy.rb: 168:in `call!'
…uby/2.1.0/gems/omniauth-1.0.3/lib/omniauth/

strategy.rb: 148:in `call'
…ruby/2.1.0/gems/omniauth-1.0.3/lib/omniauth/

builder.rb:  42:in `call'
…dle/ruby/2.1.0/gems/sass-3.2.9/lib/sass/plugin/

rack.rb:  54:in `call'
…by/2.1.0/gems/rack-cache-1.2/lib/rack/cache/

context.rb: 136:in `forward'
…by/2.1.0/gems/rack-cache-1.2/lib/rack/cache/

context.rb: 245:in `fetch'
…by/2.1.0/gems/rack-cache-1.2/lib/rack/cache/

context.rb: 185:in `lookup'
…by/2.1.0/gems/rack-cache-1.2/lib/rack/cache/

context.rb:  66:in `call!'
…by/2.1.0/gems/rack-cache-1.2/lib/rack/cache/

context.rb:  51:in `call'
…dle/ruby/2.1.0/gems/warden-1.1.1/lib/warden/

manager.rb:  35:in `block in call'
…dle/ruby/2.1.0/gems/warden-1.1.1/lib/warden/

manager.rb:  34:in `catch'
…dle/ruby/2.1.0/gems/warden-1.1.1/lib/warden/

manager.rb:  34:in `call'
…b/action_dispatch/middleware/

best_standards_support.rb:  17:in `call'
…dor/bundle/ruby/2.1.0/gems/rack-1.4.5/lib/rack/

etag.rb:  23:in `call'
…/ruby/2.1.0/gems/rack-1.4.5/lib/rack/

conditionalget.rb:  25:in `call'
…tionpack-3.2.21/lib/action_dispatch/middleware/

head.rb:  14:in `call'
…3.2.21/lib/action_dispatch/middleware/

params_parser.rb:  21:in `call'
…ionpack-3.2.21/lib/action_dispatch/middleware/

flash.rb: 242:in `call'
…/2.1.0/gems/rack-1.4.5/lib/rack/session/abstract/

id.rb: 210:in `context'
…/2.1.0/gems/rack-1.4.5/lib/rack/session/abstract/

id.rb: 205:in `call'
…npack-3.2.21/lib/action_dispatch/middleware/

cookies.rb: 341:in `call'
…s/activerecord-3.2.21/lib/active_record/

query_cache.rb:  64:in `call'
…record/connection_adapters/abstract/

connection_pool.rb: 479:in `call'
…ack-3.2.21/lib/action_dispatch/middleware/

callbacks.rb:  28:in `block in call'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb: 405:in `_run__2305709260636702136__call__3264484816793770857__callbacks'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb: 405:in `__run_callback'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb: 385:in `_run_call_callbacks'
…s/activesupport-3.2.21/lib/active_support/

callbacks.rb:  81:in `run_callbacks'
…ack-3.2.21/lib/action_dispatch/middleware/

callbacks.rb:  27:in `call'
…ack-3.2.21/lib/action_dispatch/middleware/

remote_ip.rb:  31:in `call'
…0/gems/airbrake-4.1.0/lib/airbrake/rails/

middleware.rb:  13:in `call'
….21/lib/action_dispatch/middleware/

debug_exceptions.rb:  16:in `call'
…2.21/lib/action_dispatch/middleware/

show_exceptions.rb:  56:in `call'
…by/2.1.0/gems/railties-3.2.21/lib/rails/rack/

logger.rb:  32:in `call_app'
…by/2.1.0/gems/railties-3.2.21/lib/rails/rack/

logger.rb:  16:in `block in call'
…ivesupport-3.2.21/lib/active_support/

tagged_logging.rb:  22:in `tagged'
…by/2.1.0/gems/railties-3.2.21/lib/rails/rack/

logger.rb:  16:in `call'

[Nick Coyne]

We also get these errors on heroku from time to time. I wish I knew what was causing them. A restart always solves the problem.

N.

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