ZooKeeper

Apache ZooKeeper is a well-known high-performance, centralized service providing coordination primitives. It’s frequently used with distributed applications, as all of them need this kind of synchronization in one form or another.

The most important features provided by ZooKeeper include:

• Synchronization: Reliable way to coordinate access to shared resources.
• Configuration: Centralized service for configuration management.
• Naming: Distributed naming registry.
• Group Services: Facilitates group membership and leader/followers election.

ZooKeeper is engineered with ultra large-scale systems, that require high throughput, low latency, fault-tolerance, and high availability.