= ZooKeeper =

https://zookeeper.apache.org/

ZooKeeper is a centralized service for:
 * maintain configuration information 
 * naming 
 * provide distributed synchronization
 * provide group services

https://en.wikipedia.org/wiki/Apache_ZooKeeper

Is essentially a service for distributed systems offering a '''hierarchical key-value store''', which is used to provide a distributed configuration service, synchronization service, and naming registry for large distributed systems.