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Upgrade version of MongoDB ReplicaSet

This guide will show you how to use KubeDB Ops-manager operator to upgrade the version of MongoDB ReplicaSet.

Before You Begin

  • At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.

  • Install KubeDB Provisioner and Ops-manager operator in your cluster following the steps here.

  • You should be familiar with the following KubeDB concepts:

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/mongodb directory of kubedb/docs repository.

Prepare MongoDB ReplicaSet Database

Now, we are going to deploy a MongoDB replicaset database with version 3.6.8.

Deploy MongoDB replicaset

In this section, we are going to deploy a MongoDB replicaset database. Then, in the next section we will upgrade the version of the database using MongoDBOpsRequest CRD. Below is the YAML of the MongoDB CR that we are going to create,

kind: MongoDB
  name: mg-replicaset
  namespace: demo
  version: "3.6.8-v1"
    name: "replicaset"
  replicas: 3
  storageType: Durable
    storageClassName: "standard"
    - ReadWriteOnce
        storage: 1Gi

Let’s create the MongoDB CR we have shown above,

$ kubectl create -f created

Now, wait until mg-replicaset created has status Ready. i.e,

$ k get mongodb -n demo                                                                                                                                             
NAME            VERSION    STATUS    AGE
mg-replicaset   3.6.8-v1   Ready     109s

We are now ready to apply the MongoDBOpsRequest CR to upgrade this database.

Upgrade MongoDB Version

Here, we are going to upgrade MongoDB replicaset from 3.6.8 to 4.0.5.

Create MongoDBOpsRequest:

In order to upgrade the replicaset database, we have to create a MongoDBOpsRequest CR with your desired version that is supported by KubeDB. Below is the YAML of the MongoDBOpsRequest CR that we are going to create,

kind: MongoDBOpsRequest
  name: mops-replicaset-upgrade
  namespace: demo
  type: UpdateVersion
    name: mg-replicaset
    targetVersion: 4.0.5-v3
    oplogMaxLagSeconds: 20
    objectsCountDiffPercentage: 10
  timeout: 5m
  apply: IfReady


  • specifies that we are performing operation on mg-replicaset MongoDB database.
  • spec.type specifies that we are going to perform Upgrade on our database.
  • spec.upgrade.targetVersion specifies the expected version of the database 4.0.5.
  • Have a look here on the respective sections to understand the readinessCriteria, timeout & apply fields.

Let’s create the MongoDBOpsRequest CR we have shown above,

$ kubectl apply -f .yaml created

Verify MongoDB version upgraded successfully

If everything goes well, KubeDB Ops-manager operator will update the image of MongoDB object and related StatefulSets and Pods.

Let’s wait for MongoDBOpsRequest to be Successful. Run the following command to watch MongoDBOpsRequest CR,

$ kubectl get mongodbopsrequest -n demo
Every 2.0s: kubectl get mongodbopsrequest -n demo
NAME                      TYPE            STATUS       AGE
mops-replicaset-upgrade   UpdateVersion   Successful   84s

We can see from the above output that the MongoDBOpsRequest has succeeded. If we describe the MongoDBOpsRequest we will get an overview of the steps that were followed to upgrade the database.

$ kubectl describe mongodbopsrequest -n demo mops-replicaset-upgrade
Name:         mops-replicaset-upgrade
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:
Kind:         MongoDBOpsRequest
  Creation Timestamp:  2022-10-26T10:19:55Z
  Generation:          1
  Managed Fields:
    API Version:
    Fields Type:  FieldsV1

    Manager:      kubectl-client-side-apply
    Operation:    Update
    Time:         2022-10-26T10:19:55Z
    API Version:
    Fields Type:  FieldsV1
    Manager:         kubedb-ops-manager
    Operation:       Update
    Subresource:     status
    Time:            2022-10-26T10:23:09Z
  Resource Version:  607814
  UID:               38053605-47bd-4d94-9f53-ce9474ad0a98
  Apply:  IfReady
  Database Ref:
    Name:  mg-replicaset
  Readiness Criteria:
    Objects Count Diff Percentage:  10
    Oplog Max Lag Seconds:          20
  Timeout:                          5m
  Type:                             UpdateVersion
    Target Version:  4.0.5-v3
    Last Transition Time:  2022-10-26T10:21:20Z
    Message:               MongoDB ops request is upgrading database version
    Observed Generation:   1
    Reason:                UpgradeVersion
    Status:                True
    Type:                  UpgradeVersion
    Last Transition Time:  2022-10-26T10:21:39Z
    Message:               Successfully updated statefulsets update strategy type
    Observed Generation:   1
    Reason:                UpdateStatefulSets
    Status:                True
    Type:                  UpdateStatefulSets
    Last Transition Time:  2022-10-26T10:23:09Z
    Message:               Successfully Updated Standalone Image
    Observed Generation:   1
    Reason:                UpdateStandaloneImage
    Status:                True
    Type:                  UpdateStandaloneImage
    Last Transition Time:  2022-10-26T10:23:09Z
    Message:               Successfully completed the modification process.
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
  Type    Reason                 Age    From                         Message
  ----    ------                 ----   ----                         -------
  Normal  PauseDatabase          2m27s  KubeDB Ops-manager Operator  Pausing MongoDB demo/mg-replicaset
  Normal  PauseDatabase          2m27s  KubeDB Ops-manager Operator  Successfully paused MongoDB demo/mg-replicaset
  Normal  Updating               2m27s  KubeDB Ops-manager Operator  Updating StatefulSets
  Normal  Updating               2m8s   KubeDB Ops-manager Operator  Successfully Updated StatefulSets
  Normal  UpdateStandaloneImage  38s    KubeDB Ops-manager Operator  Successfully Updated Standalone Image
  Normal  ResumeDatabase         38s    KubeDB Ops-manager Operator  Resuming MongoDB demo/mg-replicaset
  Normal  ResumeDatabase         38s    KubeDB Ops-manager Operator  Successfully resumed MongoDB demo/mg-replicaset
  Normal  Successful             38s    KubeDB Ops-manager Operator  Successfully Updated Database

Now, we are going to verify whether the MongoDB and the related StatefulSets and their Pods have the new version image. Let’s check,

$ kubectl get mg -n demo mg-replicaset -o=jsonpath='{.spec.version}{"\n"}'

$ kubectl get sts -n demo mg-replicaset -o=jsonpath='{.spec.template.spec.containers[0].image}{"\n"}'

$ kubectl get pods -n demo mg-replicaset-0 -o=jsonpath='{.spec.containers[0].image}{"\n"}'

You can see from above, our MongoDB replicaset database has been updated with the new version. So, the upgrade process is successfully completed.

Cleaning Up

To clean up the Kubernetes resources created by this tutorial, run:

kubectl delete mg -n demo mg-replicaset
kubectl delete mongodbopsrequest -n demo mops-replicaset-upgrade