Apache ZooKeeper
Open-source coordination service for distributed systems: config, naming, locks and leader election.
Updated · AppBreakup editorial · Linux, macOS, Windows, Self-hosted
Is Apache ZooKeeper free?
Yes, free and open source
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About Apache ZooKeeper
Apache ZooKeeper is a small, replicated data store that distributed applications use to agree on shared state. Clients read and write tiny records called znodes in a tree that looks like a file system, and can set watches to be told when something changes. On top of that, teams build leader election, distributed locks, service registration, cluster membership and shared configuration. A group of servers called an ensemble keeps copies of the data, so the service survives the loss of individual nodes. ZooKeeper has been the coordination layer behind Hadoop, HBase and older Kafka clusters for years, which is why many operators still run it. It is a free Apache project under the Apache 2.0 licence, written in Java, and you host and operate it yourself on Linux, macOS or Windows servers. Newer projects often choose etcd or Consul, and Kafka now ships its own KRaft mode, so ZooKeeper is mostly picked for stacks that already depend on it.
Best for: Teams running Hadoop, HBase, Solr or older Kafka stacks that need a proven coordination service..
Pros and cons
What works
- Long track record as the coordination layer for major Apache data projects
- Watches push changes to clients, so no polling is needed
- Free and open source under Apache 2.0, with two supported release lines
Why people leave
- Low-level primitives: locks and elections must be built with client recipes
- Running a healthy ensemble needs Java tuning and careful operations
- No built-in service mesh, health checks or DNS interface like Consul offers
Apache ZooKeeper vs etcd and Consul
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Top Apache ZooKeeper alternatives
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Apache ZooKeeper: common questions
What is Apache ZooKeeper?
Apache ZooKeeper: Open-source coordination service for distributed systems: config, naming, locks and leader election. Best for teams running Hadoop, HBase, Solr or older Kafka stacks that need a proven coordination service. Available for Linux, macOS and Windows, and you can host it yourself.
Is Apache ZooKeeper free?
Yes. Apache ZooKeeper is free, open-source software.
Is Apache ZooKeeper open source?
No, Apache ZooKeeper is not open source.
What platforms does Apache ZooKeeper run on?
Apache ZooKeeper is available for Linux, macOS, Windows and Self-hosted.
What are the best alternatives to Apache ZooKeeper?
The highest-ranked Apache ZooKeeper alternatives right now are etcd and Consul. See the full ranked list for pricing, platforms and verified facts.
Apache ZooKeeper vs etcd: what's the difference?
Both Apache ZooKeeper and etcd are free and open source. Both run on Linux, macOS and Windows.