Apache ZooKeeper is an open-source, distributed coordination service for highly reliable distributed applications. It offers a simple set of primitives that applications can use to build higher-level services for various purposes, such as:

• Synchronization: Coordinating the actions of multiple processes within a distributed system, ensuring they work together efficiently and consistently.

• Configuration management: Storing and managing configuration data for distributed applications, allowing them to access and update configuration dynamically.

• Group services: Enabling applications to discover and join groups of other applications, facilitating communication and collaboration.

• Leader election: Choosing a single leader process from a group of candidates for specific tasks, ensuring only one process handles a particular role at a time.

Key Features:

• Highly available: Designed to be resilient to failures and maintain service even when some nodes are unavailable.

• Scalable: Can be deployed on multiple servers to handle increasing workloads and demands.

• Fast: Performs well in read-dominant workloads, making it suitable for applications requiring frequent data access.

• Simple and efficient: Uses a familiar tree-like data model and straightforward API, making it easy for developers to integrate and use.

Common Use Cases:

• Distributed databases: Coordinating data access and maintaining consistency across multiple nodes.

• Messaging systems: Enabling message queues and brokers to manage message flow and delivery.

• Service discovery: Helping applications find and connect to other services in a dynamic environment.

• Cluster management: Coordinating tasks and configuration across a cluster of nodes.

Who uses ZooKeeper?

Many prominent companies and projects utilize ZooKeeper, including:

• Facebook

• Twitter

• Netflix

• Yahoo

• Hadoop

• HDFS