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MongoDB Standalone Volume Expansion
This guide will show you how to use KubeDB Ops-manager operator to expand the volume of a MongoDB standalone database.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectlcommand-line tool must be configured to communicate with your cluster.You must have a
StorageClassthat supports volume expansion.Install
KubeDBProvisioner and Ops-manager operator in your cluster following the steps here.You should be familiar with the following
KubeDBconcepts:
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: The yaml files used in this tutorial are stored in docs/examples/mongodb folder in GitHub repository kubedb/docs.
Expand Volume of Standalone Database
Here, we are going to deploy a MongoDB standalone using a supported version by KubeDB operator. Then we are going to apply MongoDBOpsRequest to expand its volume.
Prepare MongoDB Standalone Database
At first verify that your cluster has a storage class, that supports volume expansion. Let’s check,
$ kubectl get storageclass
NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE
standard (default) kubernetes.io/gce-pd Delete Immediate true 2m49s
We can see from the output the standard storage class has ALLOWVOLUMEEXPANSION field as true. So, this storage class supports volume expansion. We can use it.
Now, we are going to deploy a MongoDB standalone database with version 4.4.26.
Deploy MongoDB standalone
In this section, we are going to deploy a MongoDB standalone database with 1GB volume. Then, in the next section we will expand its volume to 2GB using MongoDBOpsRequest CRD. Below is the YAML of the MongoDB CR that we are going to create,
apiVersion: kubedb.com/v1
kind: MongoDB
metadata:
name: mg-standalone
namespace: demo
spec:
version: "4.4.26"
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/v2024.8.21/docs/examples/mongodb/volume-expansion/mg-standalone.yaml
mongodb.kubedb.com/mg-standalone created
Now, wait until mg-standalone has status Ready. i.e,
$ kubectl get mg -n demo
NAME VERSION STATUS AGE
mg-standalone 4.4.26 Ready 2m53s
Let’s check volume size from petset, and from the persistent volume,
$ kubectl get sts -n demo mg-standalone -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"1Gi"
$ kubectl get pv -n demo
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-d0b07657-a012-4384-862a-b4e437774287 1Gi RWO Delete Bound demo/datadir-mg-standalone-0 standard 49s
You can see the petset has 1GB storage, and the capacity of the persistent volume is also 1GB.
We are now ready to apply the MongoDBOpsRequest CR to expand the volume of this database.
Volume Expansion
Here, we are going to expand the volume of the standalone database.
Create MongoDBOpsRequest
In order to expand the volume of the database, we have to create a MongoDBOpsRequest CR with our desired volume size. Below is the YAML of the MongoDBOpsRequest CR that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: MongoDBOpsRequest
metadata:
name: mops-volume-exp-standalone
namespace: demo
spec:
type: VolumeExpansion
databaseRef:
name: mg-standalone
volumeExpansion:
standalone: 2Gi
mode: Online
Here,
spec.databaseRef.namespecifies that we are performing volume expansion operation onmg-standalonedatabase.spec.typespecifies that we are performingVolumeExpansionon our database.spec.volumeExpansion.standalonespecifies the desired volume size.spec.volumeExpansion.modespecifies the desired volume expansion mode(OnlineorOffline).
During Online VolumeExpansion KubeDB expands volume without pausing database object, it directly updates the underlying PVC. And for Offline volume expansion, the database is paused. The Pods are deleted and PVC is updated. Then the database Pods are recreated with updated PVC.
Let’s create the MongoDBOpsRequest CR we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.8.21/docs/examples/mongodb/volume-expansion/mops-volume-exp-standalone.yaml
mongodbopsrequest.ops.kubedb.com/mops-volume-exp-standalone created
Verify MongoDB Standalone volume expanded successfully
If everything goes well, KubeDB Ops-manager operator will update the volume size of MongoDB object and related PetSets and Persistent Volume.
Let’s wait for MongoDBOpsRequest to be Successful. Run the following command to watch MongoDBOpsRequest CR,
$ kubectl get mongodbopsrequest -n demo
NAME TYPE STATUS AGE
mops-volume-exp-standalone VolumeExpansion Successful 75s
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 expand the volume of the database.
$ kubectl describe mongodbopsrequest -n demo mops-volume-exp-standalone
Name: mops-volume-exp-standalone
Namespace: demo
Labels: <none>
Annotations: API Version: ops.kubedb.com/v1alpha1
Kind: MongoDBOpsRequest
Metadata:
Creation Timestamp: 2020-08-25T17:48:33Z
Finalizers:
kubedb.com
Generation: 1
Resource Version: 72899
Self Link: /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mongodbopsrequests/mops-volume-exp-standalone
UID: 007fe35a-25f6-45e7-9e85-9add488b2622
Spec:
Database Ref:
Name: mg-standalone
Type: VolumeExpansion
Volume Expansion:
Standalone: 2Gi
Status:
Conditions:
Last Transition Time: 2020-08-25T17:48:33Z
Message: MongoDB ops request is being processed
Observed Generation: 1
Reason: Scaling
Status: True
Type: Scaling
Last Transition Time: 2020-08-25T17:50:03Z
Message: Successfully updated Storage
Observed Generation: 1
Reason: VolumeExpansion
Status: True
Type: VolumeExpansion
Last Transition Time: 2020-08-25T17:50:03Z
Message: Successfully Resumed mongodb: mg-standalone
Observed Generation: 1
Reason: ResumeDatabase
Status: True
Type: ResumeDatabase
Last Transition Time: 2020-08-25T17:50:03Z
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 VolumeExpansion 29s KubeDB Ops-manager operator Successfully Updated Storage
Normal ResumeDatabase 29s KubeDB Ops-manager operator Resuming MongoDB
Normal ResumeDatabase 29s KubeDB Ops-manager operator Successfully Resumed mongodb
Normal Successful 29s KubeDB Ops-manager operator Successfully Scaled Database
Now, we are going to verify from the Petset, and the Persistent Volume whether the volume of the standalone database has expanded to meet the desired state, Let’s check,
$ kubectl get sts -n demo mg-standalone -o json | jq '.spec.volumeClaimTemplates[].spec.resources.requests.storage'
"2Gi"
$ kubectl get pv -n demo
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-d0b07657-a012-4384-862a-b4e437774287 2Gi RWO Delete Bound demo/datadir-mg-standalone-0 standard 4m29s
The above output verifies that we have successfully expanded the volume of the MongoDB standalone database.
Cleaning Up
To clean up the Kubernetes resources created by this tutorial, run:
kubectl delete mg -n demo mg-standalone
kubectl delete mongodbopsrequest -n demo mops-volume-exp-standalone