Logstash error while starting!

Hi,

I am facing a logstash issue on starting it.

[amits@localhost bin]$ ./logstash -e 'input { stdin { } } output { stdout {} }'
LoadError: no such file to load -- logstash/util/wrapped_synchronous_queue
require at org/jruby/RubyKernel.java:1040
require at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/polyglot-0.3.5/lib/polyglot.rb:65
(root) at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/logstash-core-2.4.0-java/lib/logstash/outputs/base.rb:7
require at org/jruby/RubyKernel.java:1040
require at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/polyglot-0.3.5/lib/polyglot.rb:65
(root) at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/logstash-core-2.4.0-java/lib/logstash/pipeline.rb:1
require at org/jruby/RubyKernel.java:1040
(root) at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/logstash-core-2.4.0-java/lib/logstash/pipeline.rb:11
require at org/jruby/RubyKernel.java:1040
(root) at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/logstash-core-2.4.0-java/lib/logstash/agent.rb:1
call at org/jruby/RubyProc.java:281
(root) at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/logstash-core-2.4.0-java/lib/logstash/agent.rb:10
call at org/jruby/RubyProc.java:281
(root) at /home/amits/ELK/logstash-2.4.0/vendor/bundle/jruby/1.9/gems/logstash-core-2.4.0-java/lib/logstash/runner.rb:1

Please help me in this regard and explain it also why it is bothering me for .rb files in logstash/util/wrapped_synchronous_queue folder.

Actually, their extension is NOT .rb by default its .r and I changed it to .rb, then it is working.

@magnusbaeck: How to resolve this issue?

thanks in advance.

Now it is giving following ERROR:

[amits@localhost bin]$ ./logstash -f logstash.conf
fetched an invalid config {:config=>"input { stdin { } } output { stdout {} }\n\n", :reason=>"uninitialized constant LogStash::Util::WrappedSynchronousQueue", :level=>:error}

What can be the reason?