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MySQL Volume Expansion

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

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 MySQL

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

Prepare MySQL 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 MySQL database of 3 replicas with version 8.0.35.

Deploy MySQL

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

apiVersion: kubedb.com/v1alpha2
kind: MySQL
metadata:
  name: sample-mysql
  namespace: demo
spec:
  version: "8.0.35"
  replicas: 3
  topology:
    mode: GroupReplication
  storageType: Durable
  storage:
    storageClassName: "topolvm-provisioner"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.1.26-rc.0/docs/guides/mysql/volume-expansion/volume-expansion/example/group_replication.yaml
mysql.kubedb.com/sample-mysql created

apiVersion: kubedb.com/v1alpha2
kind: MySQL
metadata:
  name: sample-mysql
  namespace: demo
spec:
  version: "8.0.31-innodb"
  replicas: 3
  topology:
    mode: InnoDBCluster
    innoDBCluster:
      router:
        replicas: 1
  storageType: Durable
  storage:
    storageClassName: "topolvm-provisioner"
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.1.26-rc.0/docs/guides/mysql/volume-expansion/volume-expansion/example/innodb.yaml
mysql.kubedb.com/sample-mysql created

apiVersion: kubedb.com/v1alpha2
kind: MySQL
metadata:
  name: sample-mysql
  namespace: demo
spec:
  version: "8.0.35"
  replicas: 3
  topology:
    mode: SemiSync
    semiSync:
      sourceWaitForReplicaCount: 1
      sourceTimeout: 23h
      errantTransactionRecoveryPolicy: PseudoTransaction
  storageType: Durable
  storage:
    storageClassName: "topolvm-provisioner"
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.1.26-rc.0/docs/guides/mysql/volume-expansion/volume-expansion/example/semi-sync.yaml
mysql.kubedb.com/sample-mysql created

apiVersion: kubedb.com/v1alpha2
kind: MySQL
metadata:
  name: sample-mysql
  namespace: demo
spec:
  version: "8.0.35"
  storageType: Durable
  storage:
    storageClassName: "topolvm-provisioner"
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi
  terminationPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.1.26-rc.0/docs/guides/mysql/volume-expansion/volume-expansion/example/standalone.yaml
mysql.kubedb.com/sample-mysql created

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

$ kubectl get mysql -n demo
NAME             VERSION   STATUS   AGE
sample-mysql     8.0.35    Ready    5m4s

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

$ kubectl get sts -n demo sample-mysql -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-mysql-0   topolvm-provisioner            63s
pvc-b90179f8-c40a-4273-ad77-74ca8470b782   1Gi        RWO            Delete           Bound    demo/data-sample-mysql-1   topolvm-provisioner            62s
pvc-f72411a4-80d5-4d32-b713-cb30ec662180   1Gi        RWO            Delete           Bound    demo/data-sample-mysql-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 MySQLOpsRequest CR to expand the volume of this database.

Volume Expansion

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

Create MySQLOpsRequest

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

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

Here,

spec.databaseRef.name specifies that we are performing volume expansion operation on sample-mysql database.
spec.type specifies that we are performing VolumeExpansion on our database.
spec.volumeExpansion.mysql 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 MySQLOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.1.26-rc.0/docs/guides/mysql/volume-expansion/volume-expansion/example/online-volume-expansion.yaml
mysqlopsrequest.ops.kubedb.com/my-online-volume-expansion created

Verify MySQL volume expanded successfully

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

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

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

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

$ kubectl describe mysqlopsrequest -n demo my-online-volume-expansion
Name:         my-online-volume-expansion
Namespace:    demo
Labels:       <none>
Annotations:  API Version:  ops.kubedb.com/v1alpha1
Kind:         MySQLOpsRequest
Metadata:
  UID:               09a119aa-4f2a-4cb4-b620-2aa3a514df11
Spec:
  Database Ref:
    Name:  sample-mysql
  Type:    VolumeExpansion
  Volume Expansion:
    mysql:  2Gi
    Mode:     Online
Status:
  Conditions:
    Last Transition Time:  2022-01-07T06:38:29Z
    Message:               Controller has started to Progress the MySQLOpsRequest: demo/my-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 MySQL pod for MySQLOpsRequest: demo/my-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 MySQL demo/my-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 MySQLOpsRequest: demo/my-online-volume-expansion
  Normal  Starting    2m1s  KubeDB Enterprise Operator  Pausing MySQL databse: demo/sample-mysql
  Normal  Successful  2m1s  KubeDB Enterprise Operator  Successfully paused MySQL database: demo/sample-mysql for MySQLOpsRequest: my-online-volume-expansion
  Normal  Successful  41s   KubeDB Enterprise Operator  Online Volume Expansion performed successfully in MySQL pod for MySQLOpsRequest: demo/my-online-volume-expansion
  Normal  Starting    41s   KubeDB Enterprise Operator  Updating MySQL storage
  Normal  Successful  41s   KubeDB Enterprise Operator  Successfully Updated MySQL storage
  Normal  Starting    41s   KubeDB Enterprise Operator  Resuming MySQL database: demo/sample-mysql
  Normal  Successful  41s   KubeDB Enterprise Operator  Successfully resumed MySQL database: demo/sample-mysql
  Normal  Successful  41s   KubeDB Enterprise Operator  Controller has Successfully expand the volume of MySQL: demo/sample-mysql

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-mysql -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-mysql-0   topolvm-provisioner            12m
pvc-b90179f8-c40a-4273-ad77-74ca8470b782   2Gi        RWO            Delete           Bound    demo/data-sample-mysql-1   topolvm-provisioner            12m
pvc-f72411a4-80d5-4d32-b713-cb30ec662180   2Gi        RWO            Delete           Bound    demo/data-sample-mysql-2   topolvm-provisioner            12m

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

Cleaning Up

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

$ kubectl delete mysql -n demo sample-mysql
$ kubectl delete mysqlopsrequest -n demo my-online-volume-expansion

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MySQL Volume Expansion

Before You Begin

Expand Volume of MySQL

Prepare MySQL Database

Deploy MySQL

Volume Expansion

Create MySQLOpsRequest

Verify MySQL volume expanded successfully

Cleaning Up

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