Zookeeper

Introduction

Apache ZooKeeper is a centralized coordination service for distributed systems, providing primitives for configuration management, naming, distributed synchronization, and group services. It exposes a hierarchical key-value namespace (znodes) with strong ordering guarantees and is widely used as the coordination backend for Kafka, HBase, Hadoop, and many legacy distributed systems.

How to Install

Starting via Binary

Quick Start

# download source
wget https://dlcdn.apache.org/zookeeper/zookeeper-3.7.1/apache-zookeeper-3.7.1-bin.tar.gz
mv apache-zookeeper-3.7.1-bin zookeeper-3.7.1 && cd zookeeper-3.7.1

Config and Boot

Config

# create data and logs dir
mkdir -p /opt/zookeeper-3.7.1/data
mkdir -p /opt/zookeeper-3.7.1/logs
cat > /opt/zookeeper-3.7.1/conf/zoo.cfg << "EOF"
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/opt/zookeeper-3.7.1/data
dataLogDir=/opt/zookeeper-3.7.1/logs
clientPort=2181
# cluster mode: service communication and election
# server.0=1.1.1.1:2888:3888
# server.1=1.1.1.2:2888:3888
# server.2=1.1.1.3:2888:3888
maxClientCnxns=300
admin.enableServer=false
EOF

# create version_id file if cluster mode
# echo 0 > /opt/zookeeper-3.7.1/data/myid
# echo 1 > /opt/zookeeper-3.7.1/data/myid
# echo 2 > /opt/zookeeper-3.7.1/data/myid

Boot(systemd)

cat > /etc/systemd/system/zookeeper.service << "EOF"
[Unit]
Description=Zookeeper Server
Documentation=https://zookeeper.apache.org/
After=network.target
Wants=network-online.target

[Service]
Type=forking
# Environment=JAVA_HOME=/opt/jdk11
ExecStart=/opt/zookeeper-3.7.1/bin/zkServer.sh start
ExecStop=/opt/zookeeper-3.7.1/bin/zkServer.sh stop
ExecReload=/opt/zookeeper-3.7.1/bin/zkServer.sh restart
Restart=on-failure
RestartSec=5s
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target
EOF

systemctl daemon-reload
systemctl start zookeeper.service
systemctl enable zookeeper.service

Starting via Docker

# https://hub.docker.com/_/zookeeper

Starting via Kubernetes

Install by Helm

# Add and update repo
helm repo add bitnami https://charts.bitnami.com/bitnami --force-update

# Get charts package
helm pull bitnami/zookeeper --untar --version=13.8.7
cd zookeeper

# Install and verify
helm -n middleware install zookeeper . --set global.storageClass=nfs-client --set replicaCount=3 --create-namespace
kubectl -n middleware exec -it zookeeper-0 -- zkServer.sh status

Reference:

1. Official Website
2. Repository