marshal data too short

My application requires to keep large data objects in session. There are like 3-4 data objects each created by parsing a csv containing 150 X 20 cells having strings of 3-4 characters. My application shows this error- "marshal data too short". I tried this-

• Deleting the old session table.
• Deleting the old migration for session table.
• Creating a new migration using rake db:sessions:create.
• editing the migration manually, changing text: data to longtext: data.
• running the migration using rake db:migrate.

other details of application--

In view "index.html.erb"- There is a link that makes ajax call to an action in controller, that action parses large csv file and makes an object out of it. this object is stored in session.

ERROR LOG

` ArgumentError in Scoring#index

Showing app/views/scoring/index.html.erb where line #4 raised:

marshal data too short

Extracted source (around line #4):

1: 
2: <form id="myForm">
3: 
4:   <%= link_to_remote "get csv file",
5:        :url      => { :action => 'show_static_1' },
6:        :update   => "static_score",
7:        :complete => "$('static_score').update(request.responseText)" %>

Application Trace | Framework Trace | Full Trace

/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:71:in `load'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:71:in `unmarshal'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:110:in `data'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:292:in `get_session'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1448:in `silence'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:288:in `get_session'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:168:in `load_session'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:62:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:62:in `load!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:70:in `stale_session_check!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:61:in `load!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:28:in `[]'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/request_forgery_protection.rb:106:in `form_authenticity_token'
(eval):2:in `send'
(eval):2:in `form_authenticity_token'
app/views/scoring/index.html.erb:4:in `_run_erb_app47views47scoring47index46html46erb'

/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:71:in `load'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:71:in `unmarshal'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:110:in `data'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:292:in `get_session'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1448:in `silence'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:288:in `get_session'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:168:in `load_session'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:62:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:62:in `load!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:70:in `stale_session_check!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:61:in `load!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:28:in `[]'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/request_forgery_protection.rb:106:in `form_authenticity_token'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/helpers/prototype_helper.rb:1065:in `options_for_ajax'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/helpers/prototype_helper.rb:449:in `remote_function'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/helpers/prototype_helper.rb:256:in `link_to_remote'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/renderable.rb:34:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/renderable.rb:34:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:306:in `with_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/renderable.rb:30:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/template.rb:205:in `render_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:265:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:348:in `_render_with_layout'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:262:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1250:in `render_for_file'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:945:in `render_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:10:in `realtime'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1326:in `default_render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1338:in `perform_action_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:617:in `call_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:610:in `perform_action_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:10:in `realtime'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/rescue.rb:160:in `perform_action_without_flash'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/flash.rb:146:in `perform_action'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `process_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:606:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:391:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:386:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/routing/route_set.rb:437:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:87:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:121:in `_call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:130:in `build_middleware_stack'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/head.rb:9:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/methodoverride.rb:24:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:15:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:122:in `call'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:29:in `call'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:9:in `cache'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:28:in `call'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/failsafe.rb:26:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `synchronize'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:114:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/reloader.rb:34:in `run'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:108:in `call'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/rack/static.rb:31:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:46:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `each'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `call'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/rack/log_tailer.rb:17:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/content_length.rb:13:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/chunked.rb:15:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/handler/mongrel.rb:64:in `process'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:159:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `each'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `run'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/handler/mongrel.rb:34:in `run'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/commands/server.rb:111
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
script/server:3

/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:71:in `load'
/usr/lib/ruby/ge开发者_开发技巧ms/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:71:in `unmarshal'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:110:in `data'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:292:in `get_session'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1448:in `silence'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/session_store.rb:288:in `get_session'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:168:in `load_session'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:62:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:62:in `load!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:70:in `stale_session_check!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:61:in `load!'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:28:in `[]'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/request_forgery_protection.rb:106:in `form_authenticity_token'
(eval):2:in `send'
(eval):2:in `form_authenticity_token'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/helpers/prototype_helper.rb:1065:in `options_for_ajax'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/helpers/prototype_helper.rb:449:in `remote_function'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/helpers/prototype_helper.rb:256:in `link_to_remote'
/app/views/scoring/index.html.erb:4:in `_run_erb_app47views47scoring47index46html46erb'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/renderable.rb:34:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/renderable.rb:34:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:306:in `with_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/renderable.rb:30:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/template.rb:205:in `render_template'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:265:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:348:in `_render_with_layout'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_view/base.rb:262:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1250:in `render_for_file'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:945:in `render_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:10:in `realtime'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:51:in `render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1326:in `default_render'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:1338:in `perform_action_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:617:in `call_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:610:in `perform_action_without_benchmark'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:10:in `realtime'
/usr/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/core_ext/benchmark.rb:17:in `ms'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/benchmarking.rb:68:in `perform_action_without_rescue'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/rescue.rb:160:in `perform_action_without_flash'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/flash.rb:146:in `perform_action'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `send'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:532:in `process_without_filters'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/filters.rb:606:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:391:in `process'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/base.rb:386:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/routing/route_set.rb:437:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:87:in `dispatch'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:121:in `_call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:130:in `build_middleware_stack'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/string_coercion.rb:25:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/head.rb:9:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/methodoverride.rb:24:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/params_parser.rb:15:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/session/abstract_store.rb:122:in `call'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:29:in `call'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in `cache'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:9:in `cache'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/query_cache.rb:28:in `call'
/usr/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/connection_adapters/abstract/connection_pool.rb:361:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/failsafe.rb:26:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `synchronize'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/lock.rb:11:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:114:in `call'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/reloader.rb:34:in `run'
/usr/lib/ruby/gems/1.8/gems/actionpack-2.3.5/lib/action_controller/dispatcher.rb:108:in `call'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/rack/static.rb:31:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:46:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `each'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:40:in `call'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/rack/log_tailer.rb:17:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/content_length.rb:13:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/chunked.rb:15:in `call'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/handler/mongrel.rb:64:in `process'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:159:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `each'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:158:in `process_client'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:285:in `run'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `initialize'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `new'
/usr/lib/ruby/gems/1.8/gems/mongrel-1.1.5/lib/mongrel.rb:268:in `run'
/usr/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/handler/mongrel.rb:34:in `run'
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/commands/server.rb:111
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require'
/usr/local/lib/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'
script/server:3

Request

Parameters:

None

Show session dump

Response

Headers:

{"Content-Type"=>"text/html",
 "Cache-Control"=>"no-cache"}

`

I met the exactly same problem.

My Rails version is 4.1.4.

I solved this problem by running:

rake tmp:clear                                      

Clear session, cache, and socket files from tmp/ (narrow w/ tmp:sessions:clear, tmp:cache:clear, tmp:sockets:clear)

Instead of the manual ALTER TABLE you could also do a migration with a limit, like this:

class FixSessionStore < ActiveRecord::Migration
  def self.up
    change_column :sessions, :data, :text, :limit => 4.megabytes
  end

  def self.down
  end
end

This will turn the column into a MEDIUMTEXT and also show up correctly in your schema.rb.

In Rails 4 development mode I had the same error and the solution was the following:

Delete all cache file from /tmp/cache/assets folder.

(Unfortunately rake assets:clean just haven't solved this problem.)

What shows up in the error log after you access the page that gives that error?

Also, what is the column type for your session information in MySQL? TEXT?

------------- EDIT BELOW ----------------

Ok, as far as I've been able to determine, this error generally means that the size of the content that you are shoving in the session is too large for the MySQL column. The most common solution cited seems to point towards a solution of changing the column from TEXT to LONGTEXT.

Try running something like this in MySQL and see if it gives you any improvement:

ALTER TABLE sessions CHANGE COLUMN data data LONGTEXT

The obvious solution is to not store the CSV data in the session as that's probably not the best place to put it, but I don't know your reasons behind what you're doing, so maybe you have no other options.

Give that a try and let me know if it worked.

The previous solutions didn't work for me. What did work for me was to clear the session's cache with

rake db:sessions:clear

This worked for me

rm -rf tmp/cache