• Version: Logstash 5.0 alpha4
• Operating System: OSX 10.10.5
• Config File

input {
  rss {
    url => "http://stackoverflow.com/feeds/tag/elasticsearch+or+logstash+or+beats+or+kibana"
    interval => 3600
  }
}
output {
 elasticsearch {
    hosts => ["localhost:9200"]
    user => "elastic"
    password => "changeme"
  }
  stdout { }
}

• Steps to Reproduce:

1. When I run Logstash with the above config file, I get the following error as mentioned in the stack.
   This seems to be a this is a rss input specific problem.

```An unknown error occurred sending a bulk request to Elasticsearch. We will retry indefinitely {:error_message=>"Failed to load class 'org.joda.time.DateTime$Access4JacksonDeserializer6e1d0360': com.fasterxml.jackson.module.afterburner.ser.BeanPropertyAccessor", :error_class=>"LogStash::Json::GeneratorError", :backtrace=>["/Users/rashmikulkarni1/Documents/ALPHA4FINAL/logstash/logstash-5.0.0-alpha4/logstash-core/lib/logstash/json.rb:52:injruby_dump'", "/Users/rashmikulkarni1/Documents/ALPHA4FINAL/logstash/logstash-5.0.0-alpha4/vendor/bundle/jruby/1.9/gems/logstash-output-elasticsearch-4.1.1-java/lib/logstash/outputs/elasticsearch/http_client.rb:49:in bulk'", "org/jruby/RubyArray.java:1613:in`each'", "org/jruby/RubyEnumerable.java:852:in `inject'", "/Users/rashmikulkarni1/Documents/ALPHA4FINAL/logstash/logstash-5.0.0-alpha4/vendor/bundle/jruby/1.9/gems/logstash-output-elasticsearch-4.1.1-java/lib/logstash/outputs/elasticsearch/http_client.rb:38:in`bulk'", "/Users/rashmikulkarni1/Documents/ALPHA4FINAL/logstash/logstash-5.0.0-alpha4/vendor/bundle/jruby/1.9/gems/logstash-output-elasticsearch-4.1.1-java/lib/logstash/outputs/elasticsearch/common.rb:181:in `safe_bulk'", "/Users/rashmikulkarni1/Documents/ALPHA4FINAL/logstash/logstash-5.0.0-alpha4/vendor/bundle/jruby/1.9/gems/logstash-output-elasticsearch-4.1.1-java/lib/logstash/outputs/elasticsearch/common.rb:105:in`submit'",