[zookeeper] TTL 기능 추가된 3.6.0

zookeeper node에 ttl 기능이 생길 예정이다. 아직 릴리즈 되지 않은 3.6.0에 추가되었다. 

https://issues.apache.org/jira/browse/ZOOKEEPER-1925

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  Fix Version/s:3.6.0

Here are only some problems with app-level cleaning:
– Slow for large trees. If the network latency is high it takes a very long time for the app to walk whole tree (e.g. 1M nodes).
– Risky. If the cleanup application crash (or becomes unreachable) it puts whole ZK cluster to danger.
– The implementation might be error-prone if multiple cleanup threads are used.

– Has to be implemented separately by each developer (until a proven implementation shared as a library).

여러 이슈가 있어서. 3.6.0으로 미룬 상태이다..

zookeeper에 ttl이 있고 성능만 좋다면 앞으로 많이 사용할 듯 싶다.