Apache ZooKeeper is a distributed configuration service, synchronization service, and naming registry. Fusion uses a ZooKeeper microservice to configure and manage all Fusion components in a single Fusion deployment.

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ZooKeeper Terms

At a high level, ZooKeeper services consist of the following components:
  • znode. ZooKeeper data is organized into a hierarchal name space of data nodes called znodes.
    A znode can have data associated with it as well as child znodes.
    The data in a znode is stored in a binary format, but it is possible to import, export, and view this information as JSON data.
    Paths to znodes are always expressed as canonical, absolute, slash-separated paths; there are no relative reference.
  • ephemeral nodes. An ephemeral node is a znode which exists only for the duration of an active session.
    When the session ends the znode is deleted. An ephemeral znode cannot have children.
  • server. A ZooKeeper service consists of one or more machines; each machine is a server which runs in its own JVM and listens on its own set of ports.
    For testing, you can run several ZooKeeper servers at once on a single workstation by configuring the ports for each server.
  • quorum. A quorum is a set of ZooKeeper servers. It must be an odd number. For most deployments, only 3 servers are required.
  • client. A client is any host or process which uses a ZooKeeper service.
The Fusion UI and API handle changes to ZooKeeper’s configuration. See the ZooKeeper Import/Export API. See the official ZooKeeper documentation for details about using and managing a ZooKeeper service.