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Upgrade version of MongoDB ReplicaSet

This guide will show you how to use KubeDB Enterprise 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 Community and Enterprise 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,

apiVersion: kubedb.com/v1alpha2
kind: MongoDB
metadata:
  name: mg-replicaset
  namespace: demo
spec:
  version: "3.6.8-v1"
  replicaSet: 
    name: "replicaset"
  replicas: 3
  storageType: Durable
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/mongodb/upgrading/mg-replicaset.yaml
mongodb.kubedb.com/mg-replicaset created

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

$ k get mongodb -n demo                                                                                                                                             
  NAME            VERSION    STATUS    AGE
  mg-replicaset   3.6.8-v1   Running   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,

apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
  name: mops-replicaset-upgrade
  namespace: demo
spec:
  type: Upgrade
  databaseRef:
    name: mg-replicaset
  upgrade:
    targetVersion: 4.0.5-v3

Here,

  • spec.databaseRef.name 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.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2020.11.12/docs/examples/mongodb/upgrading/mops-upgrade-replicaset .yaml
mongodbopsrequest.ops.kubedb.com/mops-replicaset-upgrade created

Verify MongoDB version upgraded successfully

If everything goes well, KubeDB Enterprise 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   Upgrade   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:  API Version:  ops.kubedb.com/v1alpha1
  Kind:         MongoDBOpsRequest
  Metadata:
    Creation Timestamp:  2020-08-24T14:56:39Z
    Finalizers:
      kubedb.com
    Generation:  1
    Managed Fields:
      API Version:  ops.kubedb.com/v1alpha1
      Fields Type:  FieldsV1
      fieldsV1:
        f:metadata:
          f:annotations:
            .:
            f:kubectl.kubernetes.io/last-applied-configuration:
        f:spec:
          .:
          f:databaseRef:
            .:
            f:name:
          f:type:
          f:upgrade:
            .:
            f:targetVersion:
      Manager:      kubectl
      Operation:    Update
      Time:         2020-08-24T14:56:39Z
      API Version:  ops.kubedb.com/v1alpha1
      Fields Type:  FieldsV1
      fieldsV1:
        f:metadata:
          f:finalizers:
        f:status:
          .:
          f:conditions:
          f:observedGeneration:
          f:phase:
      Manager:         kubedb-enterprise
      Operation:       Update
      Time:            2020-08-24T14:57:14Z
    Resource Version:  4812837
    Self Link:         /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-replicaset-upgrade
    UID:               99fc9dd2-11f7-44d6-9432-e93b4028ef7b
  Spec:
    Database Ref:
      Name:  mg-replicaset
    Type:    Upgrade
    Upgrade:
      Target Version:  4.0.5-v3
  Status:
    Conditions:
      Last Transition Time:  2020-08-24T14:56:39Z
      Message:               MongoDB ops request is starting to process
      Observed Generation:   1
      Reason:                UpgradingVersion
      Status:                True
      Type:                  UpgradingVersion
      Last Transition Time:  2020-08-24T14:56:39Z
      Message:               Successfully halted mongodb: mg-replicaset
      Observed Generation:   1
      Reason:                HaltDatabase
      Status:                True
      Type:                  HaltDatabase
      Last Transition Time:  2020-08-24T14:56:39Z
      Message:               Successfully updated statefulsets update strategy type
      Observed Generation:   1
      Reason:                UpdateStatefulSets
      Status:                True
      Type:                  UpdateStatefulSets
      Last Transition Time:  2020-08-24T14:57:14Z
      Message:               Successfully updated ReplicaSet images
      Observed Generation:   1
      Reason:                UpdateReplicaSetImage
      Status:                True
      Type:                  UpdateReplicaSetImage
      Last Transition Time:  2020-08-24T14:57:14Z
      Message:               Succefully Resumed mongodb: mg-replicaset
      Observed Generation:   1
      Reason:                ResumeDatabase
      Status:                True
      Type:                  ResumeDatabase
      Last Transition Time:  2020-08-24T14:57:14Z
      Message:               Successfully completed the modification process.
      Observed Generation:   1
      Reason:                Successful
      Status:                True
      Type:                  Successful
    Observed Generation:     1
    Phase:                   Successful
  Events:
    Type    Reason                 Age    From                        Message
    ----    ------                 ----   ----                        -------
    Normal  HaltDatabase          2m26s  KubeDB Enterprise Operator  Pausing Mongodb mg-replicaset in Namespace demo
    Normal  HaltDatabase          2m26s  KubeDB Enterprise Operator  Successfully Halted Mongodb mg-replicaset in Namespace demo
    Normal  Updating               2m26s  KubeDB Enterprise Operator  Updating StatefulSets
    Normal  Updating               2m26s  KubeDB Enterprise Operator  Successfully Updated StatefulSets
    Normal  UpdateReplicaSetImage  2m26s  KubeDB Enterprise Operator  Updating ReplicaSet Images
    Normal  UpdateReplicaSetImage  2m11s  KubeDB Enterprise Operator  Successfully Updated Images of Pod mg-replicaset-1
    Normal  UpdateReplicaSetImage  2m6s   KubeDB Enterprise Operator  Successfully Updated Images of Pod mg-replicaset-2
    Normal  UpdateReplicaSetImage  111s   KubeDB Enterprise Operator  Successfully Updated Images of Pod (master): mg-replicaset-0
    Normal  UpdateReplicaSetImage  111s   KubeDB Enterprise Operator  Successfully Updated ReplicaSet Images
    Normal  ResumeDatabase         111s   KubeDB Enterprise Operator  Resuming MongoDB
    Normal  ResumeDatabase         111s   KubeDB Enterprise Operator  Successfully Started Balancer
    Normal  Successful             111s   KubeDB Enterprise 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"}'                                                                                           20:59:43
  4.0.5-v3

$ kubectl get sts -n demo mg-replicaset -o=jsonpath='{.spec.template.spec.containers[0].image}{"\n"}'                                                                21:01:32
  kubedb/mongo:4.0.5-v3

$ kubectl get pods -n demo mg-replicaset-0 -o=jsonpath='{.spec.containers[0].image}{"\n"}'                                                                           21:01:57
  kubedb/mongo:4.0.5-v3

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