As a bird’s eye view, Apache Zookeeper has been leveraged to get coordination services for managing distributed applications. It holds responsibility for providing configuration information, naming, synchronization, and group services over large clusters in distributed systems. To consider as an example, Apache Kafka uses Zookeeper for choosing their leader node for the topic partitions.
zNodes
The key concept of Zookeeper is the zNode, which can be acted either as files or directories. ZNodes can be replicated between servers as they are working in a distributed file system. Znode can be described by a data structure called stats and it consolidates information about zNode context like creation time, number of changes (as version), number of children, length of stored data or zxid (ZooKeeper transaction ID) of creation, and last change. For every modification of zNodes, its version increases.