[Logstash] Event, Fields 데이터 사용방법

logstash 사용 시 event, fields 데이터 사용방법에 대한 공홈 레퍼런스 문서 입니다.
처음 사용하시는 분들에게는 유용한 자료라고 생각 되어서 공유 합니다.

https://www.elastic.co/guide/en/logstash/current/event-api.html
https://www.elastic.co/guide/en/logstash/current/event-dependent-configuration.html