#<NoMethodError: undefined method `invokable_worker_methods' for nil:NilClass>

Hi I am calling a worker from controller I am getting this error when I called. Can any one help me

#<NoMethodError: undefined method `invokabl开发者_开发知识库e_worker_methods' for nil:NilClass>
/home/web/a.a.com/vendor/plugins/backgroundrb/server/lib/master_worker.rb:129:in `worker_methods'
/home/web/a.a.com/vendor/plugins/backgroundrb/server/lib/master_worker.rb:107:in `async_method_invoke'
/home/web/a.a.com/vendor/plugins/backgroundrb/server/lib/master_worker.rb:38:in `receive_data'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_parser.rb:44:in `extract'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_parser.rb:26:in `loop'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_parser.rb:26:in `extract'
/home/web/a.a.com/vendor/plugins/backgroundrb/server/lib/master_worker.rb:32:in `receive_data'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:230:in `read_external_socket'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:222:in `handle_external_messages'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:196:in `handle_read_event'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:192:in `each'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:192:in `handle_read_event'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:146:in `start_reactor'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:139:in `loop'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_core.rb:139:in `start_reactor'
/usr/local/lib/ruby/gems/1.8/gems/packet-0.1.15/lib/packet/packet_master.rb:21:in `run'
/home/web/a.a.com/vendor/plugins/backgroundrb/server/lib/master_proxy.rb:14:in `initialize'
/home/web/a.a.com/vendor/plugins/backgroundrb/lib/backgroundrb/bdrb_start_stop.rb:109:in `new'
/home/web/a.a.com/vendor/plugins/backgroundrb/lib/backgroundrb/bdrb_start_stop.rb:109:in `start_bdrb'
/home/web/a.a.com/vendor/plugins/backgroundrb/lib/backgroundrb/bdrb_start_stop.rb:16:in `start'
/home/web/a.a.com/script/backgroundrb:24