Apache > Hadoop > ZooKeeper

ZooKeeper: Because Coordinating Distributed Systems is a Zoo

ZooKeeper is a high-performance coordination service for distributed applications. It exposes common services - such as naming, configuration management, synchronization, and group services - in a simple interface so you don't have to write them from scratch. You can use it off-the-shelf to implement consensus, group management, leader election, and presence protocols. And you can build on it for your own, specific needs.

The following documents describe concepts and procedures to get you started using ZooKeeper. If you have more questions, please ask the mailing list or browse the archives.