How To Install Apache ZooKeeper on Ubuntu 24.04 LTS

In this tutorial, we will show you how to install Apache ZooKeeper on Ubuntu 24.04 LTS. Apache ZooKeeper is a crucial component in distributed systems, providing a centralized service for maintaining configuration information, naming, and distributed synchronization. This comprehensive guide will walk you through the process of installing Apache ZooKeeper on Ubuntu 24.04 LTS, ensuring you have a robust foundation for your distributed applications.

Introduction

ZooKeeper, an open-source project under the Apache Software Foundation, offers a reliable and high-performance coordination service for distributed systems. It simplifies the development of distributed applications by providing a centralized repository for configuration management, synchronization, and group services.

Key features of Apache ZooKeeper include:

• Simple distributed coordination
• Reliability through replication
• Ordered updates
• High performance for read-dominant workloads

This guide aims to provide a step-by-step approach to installing and configuring ZooKeeper on Ubuntu 24.04 LTS, catering to both beginners and experienced system administrators.

Prerequisites

Before diving into the installation process, ensure your system meets the following requirements:

• A server running Ubuntu 24.04 LTS
• Root or sudo privileges
• Access to a terminal/command line
• An active internet connection

Minimum hardware specifications for a basic ZooKeeper setup:

• 2 CPU cores
• 4 GB RAM
• 20 GB free disk space

For production environments, consider scaling these resources based on your specific use case and expected load.

Installing Java Dependencies

ZooKeeper requires Java to run. Let’s start by installing OpenJDK, an open-source implementation of the Java Platform.

Step 1: Check Existing Java Installation

First, verify if Java is already installed on your system:

java -version

If Java is not installed, you’ll see a message indicating that the command is not found.

Step 2: Update Package Repositories

Update your system’s package index:

sudo apt update

Step 3: Install OpenJDK

Install OpenJDK 17, which is compatible with the latest ZooKeeper versions:

sudo apt install openjdk-17-jdk -y

Step 4: Verify Java Installation

After installation, verify that Java is correctly installed:

java -version

You should see output similar to:

openjdk version "17.0.x" 20xx-xx-xx
OpenJDK Runtime Environment (build 17.0.x+xx-Ubuntu-x)
OpenJDK 64-Bit Server VM (build 17.0.x+xx-Ubuntu-x, mixed mode, sharing)

Creating ZooKeeper User and Directory Structure

For security and organization, it’s best to run ZooKeeper under a dedicated user account.

Step 1: Add ZooKeeper User

Create a new system user for ZooKeeper:

sudo adduser --system --no-create-home --group zookeeper

Step 2: Set Up Home Directory

Create a home directory for ZooKeeper:

sudo mkdir /opt/zookeeper
sudo chown zookeeper:zookeeper /opt/zookeeper

Step 3: Create Data Directory

Set up a directory for ZooKeeper to store its data:

sudo mkdir /var/lib/zookeeper
sudo chown zookeeper:zookeeper /var/lib/zookeeper

Downloading and Installing ZooKeeper

Now, let’s download and install the latest stable version of Apache ZooKeeper.

Step 1: Download ZooKeeper

Navigate to the /tmp directory and download the latest ZooKeeper binary:

cd /tmp
wget https://downloads.apache.org/zookeeper/zookeeper-3.9.3/apache-zookeeper-3.9.3-bin.tar.gz

Note: Check the Apache ZooKeeper website for the latest version number and update the URL accordingly.

Step 2: Extract Archive Files

Extract the downloaded archive:

sudo tar -xzf apache-zookeeper-3.9.3-bin.tar.gz -C /opt/zookeeper --strip-components=1

Step 3: Configure Ownership and Permissions

Set the correct ownership and permissions:

sudo chown -R zookeeper:zookeeper /opt/zookeeper

Step 4: Verify Installation Files

Ensure all necessary files are present:

ls -l /opt/zookeeper

You should see directories like bin, conf, and lib, among others.

Configuring ZooKeeper

Proper configuration is crucial for ZooKeeper’s performance and security.

Step 1: Create Configuration File

Create a new configuration file based on the provided template:

sudo cp /opt/zookeeper/conf/zoo_sample.cfg /opt/zookeeper/conf/zoo.cfg

Step 2: Edit Configuration File

Open the configuration file for editing:

sudo nano /opt/zookeeper/conf/zoo.cfg

Modify or add the following essential parameters:

tickTime=2000
dataDir=/var/lib/zookeeper
clientPort=2181
initLimit=5
syncLimit=2
maxClientCnxns=60

Here’s what these parameters mean:

• tickTime: The basic time unit in milliseconds used by ZooKeeper
• dataDir: The location to store the in-memory database snapshots
• clientPort: The port to listen for client connections
• initLimit: The time limit for ZooKeeper followers to connect to a leader
• syncLimit: The time limit for followers to sync with ZooKeeper
• maxClientCnxns: The maximum number of client connections

Step 3: Advanced Configuration (Optional)

For production environments, consider adding these advanced options:

autopurge.snapRetainCount=5
autopurge.purgeInterval=24

These settings enable automatic purging of old data and snapshots, helping to manage disk space.

Security Considerations

For enhanced security, consider implementing these measures:

• Enable SSL for client-server communication
• Set up access control lists (ACLs)
• Use SASL authentication for client connections

Setting Up Systemd Service

To manage ZooKeeper as a system service, we’ll create a systemd service file.

Step 1: Create Service File

Create a new file for the ZooKeeper service:

sudo nano /etc/systemd/system/zookeeper.service

Step 2: Configure Service Parameters

Add the following content to the file:

[Unit]
Description=Apache ZooKeeper service
Documentation=http://zookeeper.apache.org
Requires=network.target
After=network.target

[Service]
Type=forking
User=zookeeper
Group=zookeeper
ExecStart=/opt/zookeeper/bin/zkServer.sh start /opt/zookeeper/conf/zoo.cfg
ExecStop=/opt/zookeeper/bin/zkServer.sh stop
ExecReload=/opt/zookeeper/bin/zkServer.sh restart
WorkingDirectory=/opt/zookeeper

[Install]
WantedBy=multi-user.target

Step 3: Set Up Auto-start

Enable the ZooKeeper service to start on boot:

sudo systemctl enable zookeeper

Starting and Testing ZooKeeper

Now that we’ve configured ZooKeeper, let’s start the service and verify its operation.

Step 1: Start ZooKeeper Service

Start the ZooKeeper service:

sudo systemctl start zookeeper

Step 2: Check Service Status

Verify that ZooKeeper is running:

sudo systemctl status zookeeper

You should see output indicating that the service is active and running.

Step 3: Basic Connectivity Testing

Test the ZooKeeper connection using the command-line interface:

/opt/zookeeper/bin/zkCli.sh -server 127.0.0.1:2181

If successful, you’ll see a ZooKeeper CLI prompt.

Using ZooKeeper CLI

The ZooKeeper CLI allows you to interact with the ZooKeeper ensemble directly.

Basic CLI Commands

Here are some essential commands to get started:

• ls /: List root-level znodes
• create /mynode "data": Create a new znode
• get /mynode: Retrieve data from a znode
• set /mynode "new data": Update znode data
• delete /mynode: Delete a znode

Troubleshooting Connection Issues

If you encounter connection problems:

• Verify that the ZooKeeper service is running
• Check firewall settings
• Ensure the client is using the correct port
• Review ZooKeeper logs for any error messages

Troubleshooting Common Issues

Even with careful installation, you might encounter some issues. Here are solutions to common problems:

Port Conflicts

If the default port (2181) is already in use:

1. Check for conflicting services: sudo netstat -tulpn | grep 2181
2. Modify the clientPort in zoo.cfg to use a different port
3. Restart the ZooKeeper service

Permission Problems

If you encounter permission denied errors:

1. Verify ownership of ZooKeeper directories: ls -l /opt/zookeeper
2. Ensure the zookeeper user has appropriate permissions
3. Check systemd service file for correct User and Group settings

Configuration Errors

For configuration-related issues:

1. Double-check zoo.cfg for syntax errors
2. Verify that all specified directories exist and are accessible
3. Review ZooKeeper logs for specific error messages

Service Startup Issues

If the ZooKeeper service fails to start:

1. Check system logs: journalctl -u zookeeper
2. Verify Java installation and JAVA_HOME environment variable
3. Ensure all required ZooKeeper files are present and accessible

Congratulations! You have successfully installed Apache ZooKeeper. Thanks for using this tutorial for installing the Apache ZooKeeper on Ubuntu 24.04 LTS system. For additional help or useful information, we recommend you check the official Apache website.