Master Distributed Locks with Zookeeper: A Step‑by‑Step Guide

In distributed systems, when multiple hosts share a resource, mutual exclusion is required to prevent interference and maintain consistency; this is achieved with a distributed lock.

Idea

Use Zookeeper to implement a simple distributed lock.

Preparation

Create a root node (e.g., Locks ) in Zookeeper for all client lock operations.

Lock Acquisition Process

Each client creates an incrementally numbered child node under Locks , receiving a sequence number that acts as a queue position. The client with the smallest number obtains the lock.

If a client’s number is not the smallest, it watches the node with the immediate smaller number; when that node disappears, the client becomes the smallest and acquires the lock.

Lock Release Process

The client releases the lock by deleting its own node; the next node in the queue receives a notification and can acquire the lock.

For example, when client A deletes its node node1 , client B, which was watching node1 , is notified that it now holds the smallest sequence number and can obtain the lock.