Deploy a Highly Available MySQL Cluster on Kubernetes – Step‑by‑Step Guide

MySQL Overview

MySQL is a popular open‑source relational database management system, widely used in web applications for its speed, low cost, and dual licensing (community and commercial).

High‑Availability Architecture

The guide adopts a master‑slave replication with read‑write separation: a single master handles writes, multiple slaves serve reads. If the master fails, traffic can be switched to a slave. Replication is asynchronous by default and can be configured per database or table.

Kubernetes Deployment Steps

1. Create a ConfigMap containing MySQL configuration files for master and slave.

apiVersion: v1
kind: ConfigMap
metadata:
  name: mysql
  labels:
    app: mysql
data:
  master.cnf: |
    [mysqld]
    log-bin
    log_bin_trust_function_creators=1
    lower_case_table_names=1
  slave.cnf: |
    [mysqld]
    super-read-only
    log_bin_trust_function_creators=1

Apply with kubectl apply -f mysql-configmap.yaml -n kube-public.

2. Create Services for the master (mysql) and read‑only endpoint (mysql‑read).

apiVersion: v1
kind: Service
metadata:
  name: mysql
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  clusterIP: None
  selector:
    app: mysql
---
apiVersion: v1
kind: Service
metadata:
  name: mysql-read
  labels:
    app: mysql
spec:
  ports:
  - name: mysql
    port: 3306
  selector:
    app: mysql

Apply with kubectl apply -f mysql-service.yaml -n kube-public.

3. Create a StatefulSet that runs three MySQL pods, mounts the ConfigMap, and provisions a dynamic PersistentVolumeClaim using an NFS storage class.

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  selector:
    matchLabels:
      app: mysql
  serviceName: mysql
  replicas: 3
  volumeClaimTemplates:
  - metadata:
      name: data
      annotations:
        volume.beta.kubernetes.io/storage-class: "nfs"
    spec:
      accessModes: ["ReadWriteOnce"]
      resources:
        requests:
          storage: 10Gi
  template:
    metadata:
      labels:
        app: mysql
    spec:
      initContainers:
      - name: init-mysql
        image: mysql:5.7
        command:
        - bash
        - "-c"
        - |
          set -ex
          [[ `hostname` =~ -([0-9]+)$ ]] || exit 1
          ordinal=${BASH_REMATCH[1]}
          echo [mysqld] > /mnt/conf.d/server-id.cnf
          echo server-id=$((100 + $ordinal)) >> /mnt/conf.d/server-id.cnf
          if [[ $ordinal -eq 0 ]]; then
            cp /mnt/config-map/master.cnf /mnt/conf.d/
          else
            cp /mnt/config-map/slave.cnf /mnt/conf.d/
          fi
      containers:
      - name: mysql
        image: mysql:5.7
        env:
        - name: MYSQL_ALLOW_EMPTY_PASSWORD
          value: "1"
        ports:
        - name: mysql
          containerPort: 3306
        volumeMounts:
        - name: data
          mountPath: /var/lib/mysql
          subPath: mysql
        - name: conf
          mountPath: /etc/mysql/conf.d
        resources:
          requests:
            cpu: 500m
            memory: 1Gi
        livenessProbe:
          exec:
            command: ["mysqladmin", "ping"]
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
        readinessProbe:
          exec:
            command: ["mysql", "-h", "127.0.0.1", "-e", "SELECT 1"]
          initialDelaySeconds: 5
          periodSeconds: 2
          timeoutSeconds: 1
      volumes:
      - name: conf
        emptyDir: {}
      - name: config-map
        configMap:
          name: mysql

Deploy with kubectl apply -f mysql-statefulset.yaml -n kube-public and monitor pods using kubectl get pods -l app=mysql -w --namespace=kube-public.

Verification

Run a temporary MySQL client container to connect to the master and create a test database:

kubectl run mysql-client --image=mysql:5.7 -it --rm --restart=Never -- mysql -h mysql-0.mysql.kube-public
CREATE DATABASE demo;
CREATE TABLE demo.messages (message VARCHAR(250));
INSERT INTO demo.messages VALUES ('hello');

Similarly, connect to the read‑only service mysql-read to verify replication.

Dynamic PVC creation requires an NFS StorageClass:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: nfs
provisioner: example.com/nfs

Apply with kubectl apply -f class.yaml.