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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 8.0.31.
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: "8.0.31"
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/v2023.02.28/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/v2023.02.28/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: "8.0.31"
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/v2023.02.28/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: "8.0.31"
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/v2023.02.28/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 8.0.31 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/v2023.02.28/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
