Error: Direct event field references (i.e. event['field']) have been disabled
in favor of using event get and set methods (e.g. event.get('field')). Please
consult the Logstash 5.0 breaking changes documentation for more details
Travis build is broken: public_suffix-2.0.4 requires ruby version >= 2.0, which is incompatible with the current version, ruby 1.9.3p551 (jruby 1.7.25)
Logstash 5.0 error:
https://www.elastic.co/guide/en/logstash/5.0/breaking-changes.html#_ruby_filter_and_custom_plugin_developers