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MySQL

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

Different vs stable/mysql

stable/mysql is deployment. k8s-mysql use the statefulset and can be deploy multi cluster with replicas.

Introduction

This chart bootstraps a single node MySQL statefulset on a Kubernetes cluster using the Helm package manager.

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 stable/mysql

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

By default a random password will be generated for the root user. If you'd like to set your own password change the mysqlRootPassword in the values.yaml.

You can retrieve your root password by running the following command. Make sure to replace [YOUR_RELEASE_NAME]:

printf $(printf '\%o' `kubectl get secret [YOUR_RELEASE_NAME]-mysql -o jsonpath="{.data.mysql-root-password[*]}"`)

Tip: List all releases using helm list

Uninstalling the Chart

To uninstall/delete the my-release :

$ helm delete --purge my-release

The command removes all the Kubernetes components associated with the chart and deletes the release completely.

Configuration

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

Parameter Description Default
args Additional arguments to pass to the MySQL container. []
initContainer.resources initContainer resource requests/limits Memory: 10Mi, CPU: 10m
image mysql image repository. mysql
imageTag mysql image tag. 5.7.30
busybox.image busybox image repository. busybox
busybox.tag busybox image tag. 1.32
testFramework.enabled test-framework switch. true
testFramework.image test-framework image repository. bats/bats
testFramework.tag test-framework image tag. 1.2.1
testFramework.imagePullPolicy test-framework image pull policy. IfNotPresent
testFramework.securityContext test-framework securityContext {}
imagePullPolicy Image pull policy IfNotPresent
existingSecret Use Existing secret for Password details nil
extraVolumes Additional volumes as a string to be passed to the tpl function
extraVolumeMounts Additional volumeMounts as a string to be passed to the tpl function
extraInitContainers Additional init containers as a string to be passed to the tpl function
extraEnvVars Additional environment variables as a string to be passed to the tpl function
mysqlRootPassword Password for the root user. Ignored if existing secret is provided Random 10 characters
mysqlUser Username of new user to create. nil
mysqlPassword Password for the new user. Ignored if existing secret is provided Random 10 characters
mysqlDatabase Name for new database to create. nil
livenessProbe.initialDelaySeconds Delay before liveness probe is initiated 30
livenessProbe.periodSeconds How often to perform the probe 10
livenessProbe.timeoutSeconds When the probe times out 5
livenessProbe.successThreshold Minimum consecutive successes for the probe to be considered successful after having failed. 1
livenessProbe.failureThreshold Minimum consecutive failures for the probe to be considered failed after having succeeded. 3
readinessProbe.initialDelaySeconds Delay before readiness probe is initiated 5
readinessProbe.periodSeconds How often to perform the probe 10
readinessProbe.timeoutSeconds When the probe times out 1
readinessProbe.successThreshold Minimum consecutive successes for the probe to be considered successful after having failed. 1
readinessProbe.failureThreshold Minimum consecutive failures for the probe to be considered failed after having succeeded. 3
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 8Gi RW
persistence.storageClass Type of persistent volume claim nil
persistence.accessMode ReadWriteOnce or ReadOnly ReadWriteOnce
persistence.existingClaim Name of existing persistent volume nil
persistence.subPath Subdirectory of the volume to mount nil
persistence.annotations Persistent Volume annotations {}
nodeSelector Node labels for pod assignment {}
affinity Affinity rules for pod assignment {}
tolerations Pod taint tolerations for deployment {}
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 nil
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
metrics.flags Additional flags for the mysql exporter to use []
metrics.serviceMonitor.enabled Set this to true to create ServiceMonitor for Prometheus operator false
metrics.serviceMonitor.additionalLabels Additional labels that can be used so ServiceMonitor will be discovered by Prometheus {}
resources CPU/Memory resource requests/limits Memory: 256Mi, CPU: 100m
configurationFiles List of mysql configuration files nil
configurationFilesPath Path of mysql configuration files /etc/mysql/conf.d/
securityContext.enabled Enable security context (mysql pod) false
securityContext.fsGroup Group ID for the container (mysql pod) 999
securityContext.runAsUser User ID for the container (mysql pod) 999
service.annotations Kubernetes annotations for mysql {}
service.type Kubernetes service type ClusterIP
service.loadBalancerIP LoadBalancer service IP ""
serviceAccount.create Specifies whether a ServiceAccount should be created false
serviceAccount.name The name of the ServiceAccount to create Generated using the mysql.fullname template
ssl.enabled Setup and use SSL for MySQL connections false
ssl.secret Name of the secret containing the SSL certificates mysql-ssl-certs
ssl.certificates[0].name Name of the secret containing the SSL certificates nil
ssl.certificates[0].ca CA certificate nil
ssl.certificates[0].cert Server certificate (public key) nil
ssl.certificates[0].key Server key (private key) nil
imagePullSecrets Name of Secret resource containing private registry credentials nil
initializationFiles List of SQL files which are run after the container started nil
timezone Container and mysqld timezone (TZ env) nil (UTC depending on image)
podAnnotations Map of annotations to add to the pods {}
podLabels Map of labels to add to the pods {}
priorityClassName Set pod priorityClassName {}
statefulsetAnnotations Map of annotations for statefulset {}
strategy Update strategy policy {type: "Recreate"}

Some of the parameters above map to the env variables defined in the MySQL DockerHub image.

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

$ helm install --name my-release \
  --set mysqlRootPassword=secretpassword,mysqlUser=my-user,mysqlPassword=my-password,mysqlDatabase=my-database \
    stable/mysql

The above command sets the MySQL root account password to secretpassword. Additionally it creates a standard database user named my-user, with the password my-password, who has access to a database named my-database.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

$ helm install --name my-release -f values.yaml stable/mysql

Tip: You can use the default values.yaml

Persistence

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

By default a PersistentVolumeClaim is created and mounted into that directory. In order to disable this functionality you can change the values.yaml to disable persistence and use an emptyDir instead.

"An emptyDir volume is first created when a Pod is assigned to a Node, and exists as long as that Pod is running on that node. When a Pod is removed from a node for any reason, the data in the emptyDir is deleted forever."

Notice: You may need to increase the value of livenessProbe.initialDelaySeconds when enabling persistence by using PersistentVolumeClaim from PersistentVolume with varying properties. Since its IO performance has impact on the database initialization performance. The default limit for database initialization is 60 seconds (livenessProbe.initialDelaySeconds + livenessProbe.periodSeconds * livenessProbe.failureThreshold). Once such initialization process takes more time than this limit, kubelet will restart the database container, which will interrupt database initialization then causing persisent data in an unusable state.

Custom MySQL configuration files

The MySQL image accepts custom configuration files at the path /etc/mysql/conf.d. If you want to use a customized MySQL configuration, you can create your alternative configuration files by passing the file contents on the configurationFiles attribute. Note that according to the MySQL documentation only files ending with .cnf are loaded.

configurationFiles:
  mysql.cnf: |-
    [mysqld]
    skip-host-cache
    skip-name-resolve
    sql-mode=STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
  mysql_custom.cnf: |-
    [mysqld]

MySQL initialization files

The MySQL image accepts *.sh, *.sql and *.sql.gz files at the path /docker-entrypoint-initdb.d. These files are being run exactly once for container initialization and ignored on following container restarts. If you want to use initialization scripts, you can create initialization files by passing the file contents on the initializationFiles attribute.

initializationFiles:
  first-db.sql: |-
    CREATE DATABASE IF NOT EXISTS first DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci;
  second-db.sql: |-
    CREATE DATABASE IF NOT EXISTS second DEFAULT CHARACTER SET utf8 DEFAULT COLLATE utf8_general_ci;

SSL

This chart supports configuring MySQL to use encrypted connections with TLS/SSL certificates provided by the user. This is accomplished by storing the required Certificate Authority file, the server public key certificate, and the server private key as a Kubernetes secret. The SSL options for this chart support the following use cases:

  • Manage certificate secrets with helm
  • Manage certificate secrets outside of helm

Manage certificate secrets with helm

Include your certificate data in the ssl.certificates section. For example:

ssl:
  enabled: false
  secret: mysql-ssl-certs
  certificates:
  - name: mysql-ssl-certs
    ca: |-
      -----BEGIN CERTIFICATE-----
      ...
      -----END CERTIFICATE-----
    cert: |-
      -----BEGIN CERTIFICATE-----
      ...
      -----END CERTIFICATE-----
    key: |-
      -----BEGIN RSA PRIVATE KEY-----
      ...
      -----END RSA PRIVATE KEY-----

Note: Make sure your certificate data has the correct formatting in the values file.

Manage certificate secrets outside of helm

  1. Ensure the certificate secret exist before installation of this chart.
  2. Set the name of the certificate secret in ssl.secret.
  3. Make sure there are no entries underneath ssl.certificates.

To manually create the certificate secret from local files you can execute:

kubectl create secret generic mysql-ssl-certs \
  --from-file=ca.pem=./ssl/certificate-authority.pem \
  --from-file=server-cert.pem=./ssl/server-public-key.pem \
  --from-file=server-key.pem=./ssl/server-private-key.pem

Note: ca.pem, server-cert.pem, and server-key.pem must be used as the key names in this generic secret.

If you are using a certificate your configurationFiles must include the three ssl lines under [mysqld]

[mysqld]
    ssl-ca=/ssl/ca.pem
    ssl-cert=/ssl/server-cert.pem
    ssl-key=/ssl/server-key.pem