Install, Visualize, and Use ZooKeeper as a Spring Cloud Registry

ZooKeeper is a top‑level open‑source distributed coordination project widely used by Dubbo, Kafka and other projects.

Introduction

ZooKeeper is a distributed coordination framework that provides consistency services for distributed systems. It was originally developed by Yahoo, later donated to the Apache Foundation, and is now a top‑level Apache project with over 9.5k stars on GitHub.

Distributed Coordination

Understanding ZooKeeper starts with the concept of distributed coordination. In a microservice system, many service instances exist; a registry coordinates service names and instance IPs, and ZooKeeper can act as this coordinator.

Installation

ZooKeeper can be installed on both Windows and Linux.

Windows Installation

Download the ZooKeeper binary package from https://www.apache.org/dyn/closer.lua/zookeeper/zookeeper-3.7.0/apache-zookeeper-3.7.0-bin.tar.gz .

Extract it to a chosen directory.

Create a configuration file

conf/zoo.cfg

with the following content:

<code># Set tick time in milliseconds
tickTime=2000
# Directory for snapshot data
dataDir=I:/developer/env/apache-zookeeper-3.7.0-bin/data
# Client connection port
clientPort=2181
</code>

Start the service from the

bin

directory:

<code>zkServer.cmd</code>

When the service starts successfully, the console displays startup information.

Linux Installation

Pull the Docker image:

<code>docker pull zookeeper:3.7.0</code>

Create a configuration directory and file

zoo.cfg

:

<code>mkdir -p /mydata/zookeeper/conf/
cd /mydata/zookeeper/conf/
touch zoo.cfg
</code>

Write the same configuration as above into

zoo.cfg

:

<code># Set tick time in milliseconds
tickTime=2000
# Directory for snapshot data
dataDir=/tmp/zookeeper
# Client connection port
clientPort=2181
</code>

Run the ZooKeeper container:

<code>docker run -p 2181:2181 --name zookeeper \
-v /mydata/zookeeper/conf/zoo.cfg:/conf/zoo.cfg \
-d zookeeper:3.7.0
</code>

Command‑line Operations

Use the zkCli tool to interact with ZooKeeper.

Connect:

<code>zkCli.cmd -server 127.0.0.1:2181</code>

List root znodes:

<code>[zk: 127.0.0.1:2181(CONNECTED) 1] ls /
[zookeeper]
</code>

Create a znode

/zk_test

with data

my_data

:

<code>[zk: 127.0.0.1:2181(CONNECTED) 2] create /zk_test my_data
Created /zk_test
</code>

Retrieve data:

<code>[zk: 127.0.0.1:2181(CONNECTED) 4] get /zk_test
my_data
</code>

Update data:

<code>[zk: 127.0.0.1:2181(CONNECTED) 5] set /zk_test test_data
[zk: 127.0.0.1:2181(CONNECTED) 6] get /zk_test
test_data
</code>

Delete the znode:

<code>[zk: 127.0.0.1:2181(CONNECTED) 7] delete /zk_test
[zk: 127.0.0.1:2181(CONNECTED) 8] ls /
[zookeeper]
</code>

Visual Management

PrettyZoo is a JavaFX‑based graphical client for ZooKeeper.

Download PrettyZoo from GitHub releases and install.

Create a connection to the ZooKeeper server; PrettyZoo supports SSH tunneling.

The UI shows the hierarchical data stored in ZooKeeper.

Right‑click a node to create or delete znodes, eliminating the need for command‑line operations.

PrettyZoo also provides a built‑in command‑line tab for advanced usage.

Node Types

ZooKeeper nodes (znodes) have four main types:

Persistent – remains after the session ends.

Persistent Sequential – persistent with an auto‑incremented suffix.

Ephemeral – removed when the session that created it closes.

Ephemeral Sequential – ephemeral with an auto‑incremented suffix.

When creating nodes via the CLI, the

-s

option adds the sequential flag and

-e

adds the ephemeral flag. Example:

<code># Create a persistent sequential node
create -s /test/seq segText
# Create an ephemeral node
create -e /test/tmp tmpText
# Create an ephemeral sequential node
create -s -e /test/seqTmp setTmpText
</code>

Using ZooKeeper as a Service Registry

ZooKeeper follows the CP model of the CAP theorem, making it suitable for service registration.

Add the Spring Cloud ZooKeeper discovery starter to

pom.xml

:

<code><dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
</dependency>
</code>

Configure

application.yml

:

<code>spring:
  cloud:
    zookeeper:
      # ZooKeeper connection string
      connect-string: localhost:2181
      discovery:
        # Register services
        register: true
        # Use IP address instead of hostname
        prefer-ip-address: true
</code>

In a sample Spring Cloud project, two services (

zookeeper-ribbon-service

and

zookeeper-user-service

) register with ZooKeeper. Using PrettyZoo you can see the service names, IPs, and ports stored as temporary nodes.

When a service shuts down, its temporary node is automatically removed, ensuring high availability.

Summary

This guide covered ZooKeeper installation on Windows and Linux, management with PrettyZoo, command‑line operations, node types, and how to use ZooKeeper as a Spring Cloud service registry, laying a foundation for further exploration such as distributed locks, leader election, or unique ID generation.