Logstash fails at logstash-filter-cipher plugin

I am using logstash : 2.2.4 and logstash-filter-cipher : 2.0.5 on linux ubuntu 14.04. I am taking input from kafka and filtering it with cipher plugin where I am decrypting message which is encrypted using aes-128-cbc, but logstash halts at cipher after handling few messages.
Here is the logstash file
bin/logstash -e 'input { kafka {topic_id => "random" zk_connect => "" codec => "plain" } } filter { cipher { algorithm => "aes-128-cbc" key =>"<key>" key_size => xx mode => "decrypt" base64 => true iv=> "ivString" }} output {stdout{codec => rubydebug}}'

Here is the output I am getting

OpenSSL::Cipher::CipherError: key not specified reset at org/jruby/ext/openssl/Cipher.java:933 init_cipher at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-cipher-2.0.5/lib/logstash/filters/cipher.rb:217 filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-cipher-2.0.5/lib/logstash/filters/cipher.rb:208 multi_filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.2.4-java/lib/logstash/filters/base.rb:151 each at org/jruby/RubyArray.java:1613 multi_filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.2.4-java/lib/logstash/filters/base.rb:148 filter_func at (eval):41 filter_batch at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.2.4-java/lib/logstash/pipeline.rb:259 each at org/jruby/RubyArray.java:1613 inject at org/jruby/RubyEnumerable.java:852 filter_batch at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.2.4-java/lib/logstash/pipeline.rb:257 worker_loop at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.2.4-java/lib/logstash/pipeline.rb:215 start_workers at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.2.4-java/lib/logstash/pipeline.rb:193

it is a bug or am I doing anything wrong ?

There was multiple thread to handle multiple input in logstash, each input thread was trying to access same cipher resource which caused this problem. This problem is already discussed at https://github.com/logstash-plugins/logstash-filter-cipher/issues/10 and now its solved by adding mutex around the resources.