Definition - What does Apache ZooKeeper mean?
Apache ZooKeeper is an open-source Apache project that is meant to allow clusters to distribute information such as configuration, naming and group services over large clusters. The project was originally a sub-project of Apache Hadoop, but was made a major project in its own right managed by the Apache Software Foundation.
Techopedia explains Apache ZooKeeper
Apache ZooKeeper is a service for providing configuration information, naming, synchronization and group services over distributed systems, including Hadoop. The rationale for the project is to make distributed systems easier to manage since many applications skimp on services that make propagating changes reliable. ZooKeeper uses a key-value store in a hierarchical fashion. It is used for high availability environments.
Apache ZooKeeper is written in Java and licensed under the Apache License 2.0. It is used by some major companies, including Rackspace, Yahoo, eBay and Reddit.