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Apache ZooKeeper

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Apache ZooKeeper Project

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The standard for distributed coordination

Naming, configuration management, synchronization, and group services battle-tested coordination primitives in a simple, highly reliable interface.

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zkCli.sh

$ bin/zkCli.sh -server 127.0.0.1:2181

Connecting to 127.0.0.1:2181

Welcome to ZooKeeper!

JLine support is enabled

[zk: 127.0.0.1:2181(CONNECTED) 0] create /myapp "config_data"

Created /myapp

[zk: 127.0.0.1:2181(CONNECTED) 1] get /myapp

config_data

[zk: 127.0.0.1:2181(CONNECTED) 2] ls /

[myapp, zookeeper]

[zk: 127.0.0.1:2181(CONNECTED) 3]

Why ZooKeeper

A proven coordination kernel trusted by Kafka, Hadoop, HBase, and many other distributed systems.

High Performance

In-memory messaging with sub-millisecond latency; handles tens of thousands of requests per second.

Simple & Reliable

A clean hierarchical namespace modeled after a file system makes coordination logic easy to reason about.

Ordered Operations

Every update is stamped with a monotonically increasing zxid, giving clients a total ordering guarantee.

Fault-Tolerant

Replicated across an ensemble of servers; survives node failures automatically with no data loss.

Use Cases

Common patterns and distributed systems problems where ZooKeeper excels.

Leader Election

Elect a single master among distributed workers reliably using ephemeral znodes and watches.

Distributed Locking

Implement mutexes and read/write locks across cluster nodes without a single point of failure.

Service Discovery

Configuration Management

Propagate config changes to all nodes instantly with watches no polling required.

Cluster Membership

Track which nodes are alive in real time using ephemeral nodes and group membership recipes.

Barrier Synchronization

Coordinate phased computations so all workers start and finish a phase together.

A Vibrant Community

ZooKeeper is a top-level Apache project with an active community of users and contributors. Join discussions, read the documentation, and help shape the roadmap.

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Getting Started

Up and running with ZooKeeper in a few simple steps.

1. Download

Grab the latest stable release and verify checksums.

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2. Quick Start

Set up a single ZooKeeper server and learn the basics of the CLI.

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3. Write a Client

Follow the basic tutorial to implement distributed primitives like barriers and queues.

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Apache ZooKeeper

Open-source coordination service for distributed applications naming, synchronization, and group services made simple.

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Copyright 2007-2026 The Apache Software Foundation. All rights reserved. Apache ZooKeeper, ZooKeeper, Apache, the Apache ZooKeeper logo and the ASF logo are either registered trademarks or trademarks of the Apache Software Foundation. All other marks mentioned may be trademarks or registered trademarks of their respective owners.

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