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ZooKeeperVersion

What is ZooKeeperVersion

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

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

ZooKeeperVersion Specification

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

apiVersion: catalog.kubedb.com/v1alpha1
kind: ZooKeeperVersion
metadata:
  annotations:
    meta.helm.sh/release-name: kubedb
    meta.helm.sh/release-namespace: kubedb
  creationTimestamp: "2024-05-02T09:41:52Z"
  generation: 1
  labels:
    app.kubernetes.io/instance: kubedb
    app.kubernetes.io/managed-by: Helm
    app.kubernetes.io/name: kubedb-catalog
    app.kubernetes.io/version: v2024.4.27
    helm.sh/chart: kubedb-catalog-v2024.4.27
  name: 3.9.1
  resourceVersion: "1455"
  uid: 3c5a4714-4ce2-4b41-8ad9-4899c3127dcc
spec:
  db:
    image: ghcr.io/appscode-images/zookeeper:3.9.1
  initContainer:
    image: ghcr.io/kubedb/zookeeper-init:3.7-v1
  securityContext:
    runAsUser: 1000
  version: 3.9.1

metadata.name

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

spec.version

spec.version is a required field that specifies the original version of ZooKeeper server 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.

The default value of this field is false. If spec.deprecated is set to true, KubeDB operator will skip processing this CRD object and will add a event to the CRD object specifying that the DB version is deprecated.

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 ZooKeeper server.

spec.initContainer.image

spec.initContainer.image is a required field that specifies the image for init container.

spec.exporter.image

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

spec.stash

This holds the Backup & Restore task definitions, where a TaskRef has a Name & Params section. Params specifies a list of parameters to pass to the task. To learn more, visit stash documentation

spec.updateConstraints

updateConstraints specifies the constraints that need to be considered during version update. Here allowList contains the versions those are allowed for updating from the current version. An empty list of AllowList indicates all the versions are accepted except the denyList. On the other hand, DenyList contains all the rejected versions for the update request. An empty list indicates no version is rejected.

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. To use a user-defined policy, the name of the policy has to be set in spec.podSecurityPolicies and in the list of allowed policy names in KubeDB operator like below:

helm upgrade -i kubedb oci://ghcr.io/appscode-charts/kubedb \
  --namespace kubedb --create-namespace \
  --set additionalPodSecurityPolicies[0]=custom-db-policy \
  --set-file global.license=/path/to/the/license.txt \
  --set gloabal.featureGates.ZooKeeper=true \
  --wait --burst-limit=10000 --debug

Next Steps

• Learn about ZooKeeper crd here.
• Deploy your first ZooKeeper server with KubeDB by following the guide here.