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PerconaXtraDB Volume Expansion

This guide will show you how to use KubeDB Enterprise operator to expand the volume of a PerconaXtraDB.

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.
You must have a StorageClass that supports volume expansion.
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

Expand Volume of PerconaXtraDB

Here, we are going to deploy a PerconaXtraDB cluster using a supported version by KubeDB operator. Then we are going to apply PerconaXtraDBOpsRequest to expand its volume. The process of expanding PerconaXtraDB standalone is same as PerconaXtraDB cluster.

Prepare PerconaXtraDB 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)    rancher.io/local-path   Delete          WaitForFirstConsumer   false                  69s
topolvm-provisioner   topolvm.cybozu.com      Delete          WaitForFirstConsumer   true                   37s

We can see from the output the topolvm-provisioner storage class has ALLOWVOLUMEEXPANSION field as true. So, this storage class supports volume expansion. We will use this storage class. You can install topolvm from here.

Now, we are going to deploy a PerconaXtraDB database of 3 replicas with version 8.0.26.

Deploy PerconaXtraDB

In this section, we are going to deploy a PerconaXtraDB Cluster with 1GB volume. Then, in the next section we will expand its volume to 2GB using PerconaXtraDBOpsRequest CRD. Below is the YAML of the PerconaXtraDB CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: PerconaXtraDB
metadata:
  name: sample-pxc
  namespace: demo
spec:
  version: "8.0.26"
  replicas: 3
  storageType: Durable
  storage:
    storageClassName: "topolvm-provisioner"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2023.08.18/docs/guides/percona-xtradb/volume-expansion/volume-expansion/example/sample-pxc.yaml
perconaxtradb.kubedb.com/sample-pxc created

Now, wait until sample-pxc has status Ready. i.e,

$ kubectl get perconaxtradb -n demo
NAME             VERSION   STATUS   AGE
sample-pxc   8.0.26    Ready    5m4s

Let’s check volume size from statefulset, and from the persistent volume,

$ kubectl get sts -n demo sample-pxc -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-331335d1-c8e0-4b73-9dab-dae57920e997   1Gi        RWO            Delete           Bound    demo/data-sample-pxc-0   topolvm-provisioner            63s
pvc-b90179f8-c40a-4273-ad77-74ca8470b782   1Gi        RWO            Delete           Bound    demo/data-sample-pxc-1   topolvm-provisioner            62s
pvc-f72411a4-80d5-4d32-b713-cb30ec662180   1Gi        RWO            Delete           Bound    demo/data-sample-pxc-2   topolvm-provisioner            62s

You can see the statefulset has 1GB storage, and the capacity of all the persistent volumes are also 1GB.

We are now ready to apply the PerconaXtraDBOpsRequest CR to expand the volume of this database.

Volume Expansion

Here, we are going to expand the volume of the PerconaXtraDB cluster.

Create PerconaXtraDBOpsRequest

In order to expand the volume of the database, we have to create a PerconaXtraDBOpsRequest CR with our desired volume size. Below is the YAML of the PerconaXtraDBOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: PerconaXtraDBOpsRequest
metadata:
  name: px-online-volume-expansion
  namespace: demo
spec:
  type: VolumeExpansion  
  databaseRef:
    name: sample-pxc
  volumeExpansion:   
    mode: "Online"
    perconaxtradb: 2Gi

Here,

spec.databaseRef.name specifies that we are performing volume expansion operation on sample-pxc database.
spec.type specifies that we are performing VolumeExpansion on our database.
spec.volumeExpansion.perconaxtradb specifies the desired volume size.
spec.volumeExpansion.mode specifies the desired volume expansion mode (Online or Offline). Storageclass topolvm-provisioner supports Online volume expansion.

Note: If the Storageclass you are using doesn’t support Online Volume Expansion, Try offline volume expansion by using spec.volumeExpansion.mode:"Offline".

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2023.08.18/docs/guides/percona-xtradb/volume-expansion/volume-expansion/example/online-volume-expansion.yaml
perconaxtradbopsrequest.ops.kubedb.com/px-online-volume-expansion created

Verify PerconaXtraDB volume expanded successfully

If everything goes well, KubeDB Enterprise operator will update the volume size of PerconaXtraDB object and related StatefulSets and Persistent Volumes.

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

$ kubectl get perconaxtradbopsrequest -n demo
NAME                         TYPE              STATUS       AGE
px-online-volume-expansion   VolumeExpansion   Successful   96s

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

$ kubectl describe perconaxtradbopsrequest -n demo px-online-volume-expansion
Name:         px-online-volume-expansion
Namespace:    demo
Labels:       <none>
Annotations:  API Version:  ops.kubedb.com/v1alpha1
Kind:         PerconaXtraDBOpsRequest
Metadata:
  UID:               09a119aa-4f2a-4cb4-b620-2aa3a514df11
Spec:
  Database Ref:
    Name:  sample-pxc
  Type:    VolumeExpansion
  Volume Expansion:
    PerconaXtraDB:  2Gi
    Mode:     Online
Status:
  Conditions:
    Last Transition Time:  2022-01-07T06:38:29Z
    Message:               Controller has started to Progress the PerconaXtraDBOpsRequest: demo/px-online-volume-expansion
    Observed Generation:   1
    Reason:                OpsRequestProgressingStarted
    Status:                True
    Type:                  Progressing
    Last Transition Time:  2022-01-07T06:39:49Z
    Message:               Online Volume Expansion performed successfully in PerconaXtraDB pod for PerconaXtraDBOpsRequest: demo/px-online-volume-expansion
    Observed Generation:   1
    Reason:                SuccessfullyVolumeExpanded
    Status:                True
    Type:                  VolumeExpansion
    Last Transition Time:  2022-01-07T06:39:49Z
    Message:               Controller has successfully expand the volume of PerconaXtraDB demo/px-online-volume-expansion
    Observed Generation:   1
    Reason:                OpsRequestProcessedSuccessfully
    Status:                True
    Type:                  Successful
  Observed Generation:     3
  Phase:                   Successful
Events:
  Type    Reason      Age   From                        Message
  ----    ------      ----  ----                        -------
  Normal  Starting    2m1s  KubeDB Enterprise Operator  Start processing for PerconaXtraDBOpsRequest: demo/px-online-volume-expansion
  Normal  Starting    2m1s  KubeDB Enterprise Operator  Pausing PerconaXtraDB databse: demo/sample-pxc
  Normal  Successful  2m1s  KubeDB Enterprise Operator  Successfully paused PerconaXtraDB database: demo/sample-pxc for PerconaXtraDBOpsRequest: px-online-volume-expansion
  Normal  Successful  41s   KubeDB Enterprise Operator  Online Volume Expansion performed successfully in PerconaXtraDB pod for PerconaXtraDBOpsRequest: demo/px-online-volume-expansion
  Normal  Starting    41s   KubeDB Enterprise Operator  Updating PerconaXtraDB storage
  Normal  Successful  41s   KubeDB Enterprise Operator  Successfully Updated PerconaXtraDB storage
  Normal  Starting    41s   KubeDB Enterprise Operator  Resuming PerconaXtraDB database: demo/sample-pxc
  Normal  Successful  41s   KubeDB Enterprise Operator  Successfully resumed PerconaXtraDB database: demo/sample-pxc
  Normal  Successful  41s   KubeDB Enterprise Operator  Controller has Successfully expand the volume of PerconaXtraDB: demo/sample-pxc

Now, we are going to verify from the Statefulset, and the Persistent Volumes whether the volume of the database has expanded to meet the desired state, Let’s check,

$ kubectl get sts -n demo sample-pxc -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-331335d1-c8e0-4b73-9dab-dae57920e997   2Gi        RWO            Delete           Bound    demo/data-sample-pxc-0   topolvm-provisioner            12m
pvc-b90179f8-c40a-4273-ad77-74ca8470b782   2Gi        RWO            Delete           Bound    demo/data-sample-pxc-1   topolvm-provisioner            12m
pvc-f72411a4-80d5-4d32-b713-cb30ec662180   2Gi        RWO            Delete           Bound    demo/data-sample-pxc-2   topolvm-provisioner            12m

The above output verifies that we have successfully expanded the volume of the PerconaXtraDB database.

Cleaning Up

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

$ kubectl delete perconaxtradb -n demo sample-pxc
$ kubectl delete perconaxtradbopsrequest -n demo px-online-volume-expansion

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