Thanks, that helps a lot... Apparently there is something wrong with this:
event.set('subject_decoded') =Mail::Encodings.value_decode(event.get('subject'))
DEBUG: exec /usr/share/logstash/vendor/jruby/bin/jruby /usr/share/logstash/lib/bootstrap/environment.rb logstash/runner.rb --path.settings /etc/logstash/ -f .
Sending Logstash's logs to /opt/logstash/logs which is now configured via log4j2.properties
SyntaxError: (ruby filter code):1: syntax error, unexpected '='
@codeblock = lambda { |event, &new_event_block| event.set('b64_decoded') = Base64.decode64(event.get('subject')) }
^
eval at org/jruby/RubyKernel.java:1079
register at /usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-ruby-3.0.2/lib/logstash/filters/ruby.rb:38
register at /usr/share/logstash/vendor/jruby/lib/ruby/1.9/forwardable.rb:201
start_workers at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:235
each at org/jruby/RubyArray.java:1613
start_workers at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:235
run at /usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:188
start_pipeline at /usr/share/logstash/logstash-core/lib/logstash/agent.rb:302
Going to do some more digging and fiddeling...