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MongoDBVersion

What is MongoDBVersion

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

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

MongoDBVersion Spec

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

apiVersion: catalog.kubedb.com/v1alpha1
kind: MongoDBVersion
metadata:
  name: "4.2.3"
  labels:
    app: kubedb
spec:
  db:
    image: mongo:4.2.3
  distribution: Official
  exporter:
    image: kubedb/mongodb_exporter:v0.32.0
  initContainer:
    image: kubedb/mongodb-init:4.2-v7
  podSecurityPolicies:
    databasePolicyName: mongodb-db
  replicationModeDetector:
    image: kubedb/replication-mode-detector:v0.16.0
  stash:
    addon:
      backupTask:
        name: mongodb-backup-4.2.3
      restoreTask:
        name: mongodb-restore-4.2.3
  updateConstraints:
    allowlist:
      - '>= 4.4.0, < 5.0.0'
  version: 4.2.3

metadata.name

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

We follow this convention for naming MongoDBVersion crd:

• Name format: {Original MongoDB image verion}-{modification tag}

We modify original MongoDB docker image to support MongoDB clustering and re-tag the image with v1, v2 etc. modification tag. An image with higher modification tag will have more features than the images with lower modification tag. Hence, it is recommended to use MongoDBVersion crd with highest modification tag to enjoy the latest features.

spec.version

spec.version is a required field that specifies the original version of MongoDB 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/mongo:3.6 docker image to support MongoDB clustering and re-tagged as kubedb/mongo:3.6-v1. So, we have marked kubedb/mongo:3.6 as deprecated for KubeDB 0.9.0-rc.0.

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 MongoDB database.

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.

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.

helm upgrade kubedb-operator appscode/kubedb --namespace kube-system \
  --set additionalPodSecurityPolicies[0]=custom-db-policy \
  --set additionalPodSecurityPolicies[1]=custom-snapshotter-policy

Next Steps

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