What is Zookeeper

 1. Zookeeper provides multiple features for distributed applications:

    - Distributed configuration management

    - Self election / consensus building

    - Coordination and locks.

    - Key value store

2. Zookeeper is used in many distributed systems, such as Hadoop, Kafka, etc...

3. It's an Apache Project that's proven to be very stable and hasn't had major release in many years

4. 3.4.x is the stable channel

    3.5.x has been in development for manyu years, and it is still in beta

5. Zookeeper internal data structure is like a tree

- Each node is called a zNode

- Each zNode has a path

- zNode can be persistent or ephemeral

- Each zNode can store data

- No renaming of zNode

- Each zNode can be WATCHed for changes