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MySQLVersion

What is MySQLVersion

MySQLVersion is a Kubernetes Custom Resource Definitions (CRD). It provides a declarative configuration to specify the docker images to be used for MySQL database deployed with KubeDB in a Kubernetes native way.

When you install KubeDB, a MySQLVersion custom resource will be created automatically for every supported MySQL versions. You have to specify the name of MySQLVersion crd in spec.version field of MySQL crd. Then, KubeDB will use the docker images specified in the MySQLVersion crd to create your expected database.

Using a separate crd for specifying respective docker images, and pod security policy names allow us to modify the images, and policies independent of KubeDB operator. This will also allow the users to use a custom image for the database.

MySQLVersion Specification

As with all other Kubernetes objects, a MySQLVersion needs apiVersion, kind, and metadata fields. It also needs a .spec section.

	apiVersion: catalog.kubedb.com/v1alpha1
kind: MySQLVersion
metadata:
  labels:
    app.kubernetes.io/instance: kubedb-catalog
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: kubedb-catalog
    app.kubernetes.io/version: v0.14.0-beta.1
    helm.sh/chart: kubedb-catalog-v0.14.0-beta.1
  name: 8.0.21
spec:
  db:
    image: kubedb/mysql:8.0.21
  exporter:
    image: kubedb/mysqld-exporter:v0.11.0
  initContainer:
    image: kubedb/busybox
  podSecurityPolicies:
    databasePolicyName: mysql-db
  replicationModeDetector:
    image: kubedb/mysql-replication-mode-detector:v0.1.0-beta.1
  tools:
    image: kubedb/mysql-tools:5.7.25
  upgradeConstraints:
    denylist:
      groupReplication:
      - < 8.0.21
      standalone:
      - < 8.0.21
  version: 8.0.21

metadata.name

metadata.name is a required field that specifies the name of the MySQLVersion crd. You have to specify this name in spec.version field of MySQL crd.

We follow this convention for naming MySQLVersion crd:

  • Name format: {Original MySQL image version}-{modification tag}

We modify original MySQL docker image to support additional features. An image with higher modification tag will have more features than the images with lower modification tag. Hence, it is recommended to use MySQLVersion crd with highest modification tag to take advantage of the latest features.

spec.version

spec.version is a required field that specifies the original version of MySQL database that has been used to build the docker image specified in spec.db.image field.

spec.deprecated

spec.deprecated is an optional field that specifies whether the docker images specified here is supported by the current KubeDB operator. For example, we have modified kubedb/mysql:8.0 docker image to support custom configuration and re-tagged as kubedb/mysql:8.0-v2. Now, KubeDB 0.9.0-rc.0 supports providing custom configuration which required kubedb/mysql:8.0-v2 docker image. So, we have marked kubedb/mysql:8.0 as deprecated for KubeDB 0.9.0-rc.0.

The default value of this field is false. If spec.deprecated is set true, KubeDB operator will not create the database and other respective resources for this version.

spec.db.image

spec.db.image is a required field that specifies the docker image which will be used to create Statefulset by KubeDB operator to create expected MySQL database.

spec.exporter.image

spec.exporter.image is a required field that specifies the image which will be used to export Prometheus metrics.

spec.initContainer.image

spec.initContainer.image is a required field that specifies the image which will be used to remove lost+found directory and mount an EmptyDir data volume.

spec.replicationModeDetector.image

spec.replicationModeDetector.image is only required field for MySQL Group Replication. This field specifies that image which will be used to detect primary member/replica/node in Group Replication.

spec.tools.image

spec.tools.image is a optional field that specifies the image which will be used to take backup and initialize database from snapshot.

spec.upgradeConstraints

spec.upgradeConstraints specifies a specific database version upgrade constraints in a mathematical expression that describes whether it is possible or not to upgrade from the current version to any other valid version. This field consists of the following sub-fields:

  • denylist specifies that it is not possible to upgrade from the current version to any other version. This field has two sub-fields:
    • groupReplication : Suppose you have an expression like, < 8.0.21 under groupReplication, it indicates that it’s not possible to upgrade from the current version to any other lower version 8.0.21 for group replication.
    • standalone: Suppose you have an expression like, < 8.0.21 under standalone, it indicates that it’s not possible to upgrade from the current version to any other lower version 8.0.21 for standalone.
  • allowlist specifies that it is possible to upgrade from the current version to any other version. This field has two sub-fields:
    • groupReplication : Suppose you have an expression like, 8.0.3, it indicates that it’s possible to upgrade from the current version to 8.0.3 for group replication.
    • standalone: Suppose you have an expression like, 8.0.3, it indicates that it’s possible to upgrade from the current version to 8.0.3 for standalone.

spec.podSecurityPolicies.databasePolicyName

spec.podSecurityPolicies.databasePolicyName is a required field that specifies the name of the pod security policy required to get the database server pod(s) running.

Next Steps

  • Learn about MySQL crd here.
  • Deploy your first MySQL database with KubeDB by following the guide here.