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MemcachedVersion

What is MemcachedVersion

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

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

MemcachedVersion Specification

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

apiVersion: catalog.kubedb.com/v1alpha1
kind: MemcachedVersion
metadata:
  name: "1.5.4-v1"
  labels:
    app: kubedb
spec:
  version: "1.5.4"
  db:
    image: "${KUBEDB_DOCKER_REGISTRY}/memcached:1.5.4-v1"
  exporter:
    image: "${KUBEDB_DOCKER_REGISTRY}/memcached-exporter:v0.4.1"
  podSecurityPolicies:
    databasePolicyName: "memcached-db"

metadata.name

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

We follow this convention for naming MemcachedVersion crd:

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

We modify original Memcached 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 MemcachedVersion 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 Memcached 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. For example, we have modified kubedb/memcached:1.5.4 docker image to support custom configuration and re-tagged as kubedb/memcached:1.5.4-v1. Now, KubeDB 0.9.0-rc.0 supports providing custom configuration which required kubedb/memcached:1.5.4-v1 docker image. So, we have marked kubedb/memcached:1.5.4 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 Memcached server.

spec.exporter.image

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

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 polict has to be set in spec.podSecurityPolicies and in the list of allowed policy names in KubeDB operator like below:

helm upgrade kubedb-operator appscode/kubedb --namespace kube-system \
  --set additionalPodSecurityPolicies[0]=custom-db-policy

Next Steps

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