Logstash ruby filter to truncate messages that are too long to make it to elasticsearch

logstash.conf

filter {
   ruby {
        code => "event.set('message_size', event.get('message').bytesize) if event.get('message')"
    }
    ruby {
        code => "
          if (event.get('message_size'))
                event.set('message', event.get('message')[0..9999]) if event.get('message_size') > 32000
                event.tag 'long message'  if event.get('message_size') > 32000
          end
        "
    }
}