MySQL - Single Master, Multiple Slaves

MySQL is one of the most popular database servers in the world. Notable users include Wikipedia, Facebook and Google.

Introduction

This chart bootstraps a single master and multiple slave MySQL deployment on a Kubernetes cluster using the Helm package manager. Largely inspired by this tutorial, further work was made to 'production-ize' the example.

Prerequisites

• Kubernetes 1.10+ with Beta APIs enabled
• PV provisioner support in the underlying infrastructure

Installing the Chart

To install the chart with the release name my-release:

$ helm install --name my-release incubator/mysqlha

The command deploys MySQL cluster on the Kubernetes cluster in the default configuration. The configuration section lists the parameters that can be configured during installation.

Uninstall

To uninstall/delete the my-release deployment:

$ helm delete my-release

Configuration

The following table lists the configurable parameters of the MySQL chart and their default values.

Parameter	Description	Default
mysqlImage	mysql image and tag.	mysql:5.7.13
xtraBackupImage	xtrabackup image and tag.	gcr.io/google-samples/xtrabackup:1.0
imagePullPolicy	Image pull policy.	IfNotPresent
nameOverride	String to partially override mysqlha.fullname template with a string (will prepend the release name)	nil
fullnameOverride	String to fully override mysqlha.fullname template with a string	nil
replicaCount	Number of MySQL replicas	3
mysqlRootPassword	Password for the root user.	Randomly generated
mysqlUser	Username of new user to create.	nil
mysqlPassword	Password for the new user.	Randomly generated
mysqlReplicationUser	Username for replication user	repl
mysqlReplicationPassword	Password for replication user.	Randomly generated
mysqlDatabase	Name of the new Database to create	nil
configFiles.master.cnf	Master configuration file	See values.yaml
configFiles.slave.cnf	Slave configuration file	See values.yaml
podAnnotations	Pod annotations	nil
schedulerName	Name of the k8s scheduler (other than default)	nil
persistence.enabled	Create a volume to store data	true
persistence.size	Size of persistent volume claim	10Gi
persistence.storageClass	Type of persistent volume claim	nil
persistence.accessModes	Persistent volume access modes	[ReadWriteOnce]
persistence.annotations	Persistent volume annotations	{}
resources	CPU/Memory resource requests/limits	Memory: 128Mi, CPU: 100m
metrics.enabled	Start a side-car prometheus exporter	false
metrics.image	Exporter image	prom/mysqld-exporter
metrics.imageTag	Exporter image	v0.10.0
metrics.imagePullPolicy	Exporter image pull policy	IfNotPresent
metrics.resources	Exporter resource requests/limit	See values.yaml
metrics.livenessProbe.initialDelaySeconds	Delay before metrics liveness probe is initiated	15
metrics.livenessProbe.timeoutSeconds	When the probe times out	5
metrics.readinessProbe.initialDelaySeconds	Delay before metrics readiness probe is initiated	5
metrics.readinessProbe.timeoutSeconds	When the probe times out	1

Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,

Persistence

The MySQL image stores the MySQL data and configurations at the /var/lib/mysql path of the container.

By default persistence is enabled, and a PersistentVolumeClaim is created and mounted in that directory. As a result, a persistent volume will need to be defined:

# https://kubernetes.io/docs/user-guide/persistent-volumes/#azure-disk
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: fast
provisioner: kubernetes.io/azure-disk
parameters:
  skuName: Premium_LRS
  location: westus

In order to disable this functionality you can change the values.yaml to disable persistence and use an emptyDir instead.

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