Book Image

Apache ZooKeeper Essentials

By : Saurav Haloi
Book Image

Apache ZooKeeper Essentials

By: Saurav Haloi

Overview of this book

Table of Contents (14 chapters)
Apache ZooKeeper Essentials
About the Author
About the Reviewers
Performing Common Distributed System Tasks

The ZooKeeper data model

As defined by the ZooKeeper wiki, ZooKeeper allows distributed processes to coordinate with each other through a shared hierarchical namespace of data registers. The namespace looks quite similar to a Unix filesystem. The data registers are known as znodes in the ZooKeeper nomenclature. You can see examples of znodes in the following image:

A ZooKeeper's hierarchical namespace

Here, you can see that znodes are organized hierarchically, much like a tree, as a standard filesystem. Some important points to take note of are as follows:

  • The root node has one child znode called /zoo, which in turn has three znodes.

  • Every znode in the ZooKeeper tree is identified by a path, and the path elements are separated by /.

  • The znodes are called data registers because they can store data. Thus, a znode can have children as well as data associated with it. It's analogous to having a filesystem that allows a file to also be a path.

The data in a znode is typically stored in a byte format...