Skip to main content
Version: Preview

Scale for a MySQL cluster

You can scale a MySQL cluster in two ways, vertical scaling and horizontal scaling.

From v0.9.0, for MySQL and PostgreSQL, after vertical scaling or horizontal scaling is performed, KubeBlocks automatically matches the appropriate configuration template based on the new specification. This is the KubeBlocks dynamic configuration feature. This feature simplifies the process of configuring parameters, saves time and effort and reduces performance issues caused by incorrect configuration. For detailed instructions, refer to Configuration.

Vertical scaling​

You can vertically scale a cluster by changing resource requirements and limits (CPU and storage). For example, if you need to change the resource class from 1C2G to 2C4G, vertical scaling is what you need.

note

During the vertical scaling process, all pods restart and the pod role may change after the restarting.

Before you start​

Check whether the cluster status is Running. Otherwise, the following operations may fail.

kubectl get cluster mycluster
>
NAME        CLUSTER-DEFINITION   VERSION        TERMINATION-POLICY   STATUS    AGE
mycluster   mysql                mysql-8.0.33   Delete               Running   4d18h

Steps​

There are two ways to apply vertical scaling.

  1. Apply an OpsRequest to the specified cluster. Configure the parameters according to your needs.

    kubectl apply -f - <<EOF
    apiVersion: apps.kubeblocks.io/v1alpha1
    kind: OpsRequest
    metadata:
      name: ops-vertical-scaling
      namespace: demo
    spec:
      clusterName: mycluster
      type: VerticalScaling
      verticalScaling:
      - componentName: mysql
        requests:
          memory: "2Gi"
          cpu: "1"
        limits:
          memory: "4Gi"
          cpu: "2"
    EOF

  2. Check the operation status to validate the vertical scaling.

    kubectl get ops -n demo
    >
    NAMESPACE   NAME                   TYPE              CLUSTER     STATUS    PROGRESS   AGE
    demo        ops-vertical-scaling   VerticalScaling   mycluster   Succeed   3/3        6m

    If an error occurs to the vertical scaling operation, you can troubleshoot with kubectl describe ops -n demo command to view the events of this operation.

  3. Check whether the corresponding resources change.

    kubectl describe cluster mycluster -n demo

Horizontal scaling​

Horizontal scaling changes the amount of pods. For example, you can apply horizontal scaling to scale pods up from three to five. The scaling process includes the backup and restore of data.

Before you start​

Check whether the cluster STATUS is Running. Otherwise, the following operations may fail.

kubectl get cluster mycluster
>
NAME        CLUSTER-DEFINITION   VERSION        TERMINATION-POLICY   STATUS    AGE
mycluster   mysql                mysql-8.0.33   Delete               Running   4d19h

Steps​

There are two ways to apply horizontal scaling.

  1. Apply an OpsRequest to a specified cluster. Configure the parameters according to your needs.

    kubectl apply -f - <<EOF
    apiVersion: apps.kubeblocks.io/v1alpha1
    kind: OpsRequest
    metadata:
      name: ops-horizontal-scaling
      namespace: demo
    spec:
      clusterName: mycluster
      type: HorizontalScaling
      horizontalScaling:
      - componentName: mysql
        replicas: 1
    EOF

  2. Check the operation status to validate the horizontal scaling.

    kubectl get ops -n demo
    >
    NAMESPACE   NAME                     TYPE                CLUSTER     STATUS    PROGRESS   AGE
    demo        ops-horizontal-scaling   HorizontalScaling   mycluster   Succeed   3/3        6m

    If an error occurs to the horizontal scaling operation, you can troubleshoot with kubectl describe ops -n demo command to view the events of this operation.

  3. Check whether the corresponding resources change.

    kubectl describe cluster mycluster -n demo

Handle the snapshot exception​

If STATUS=ConditionsError occurs during the horizontal scaling process, you can find the cause from cluster.status.condition.message for troubleshooting. In the example below, a snapshot exception occurs.

Status:
  conditions: 
  - lastTransitionTime: "2023-02-08T04:20:26Z"
    message: VolumeSnapshot/mycluster-mysql-scaling-dbqgp: Failed to set default snapshot
      class with error cannot find default snapshot class
    reason: ApplyResourcesFailed
    status: "False"
    type: ApplyResources

Reason

This exception occurs because the VolumeSnapshotClass is not configured. This exception can be fixed after configuring VolumeSnapshotClass, but the horizontal scaling cannot continue to run. It is because the wrong backup (volumesnapshot is generated by backup) and volumesnapshot generated before still exist. First, delete these two wrong resources and then KubeBlocks re-generates new resources.

Steps:

  1. Configure the VolumeSnapshotClass by running the command below.

    kubectl create -f - <<EOF
    apiVersion: snapshot.storage.k8s.io/v1
    kind: VolumeSnapshotClass
    metadata:
      name: csi-aws-vsc
      annotations:
        snapshot.storage.kubernetes.io/is-default-class: "true"
    driver: ebs.csi.aws.com
    deletionPolicy: Delete
    EOF

  2. Delete the wrong backup (volumesnapshot is generated by backup) and volumesnapshot resources.

    kubectl delete backup -l app.kubernetes.io/instance=mycluster

    kubectl delete volumesnapshot -l app.kubernetes.io/instance=mycluster

Result

The horizontal scaling continues after backup and volumesnapshot are deleted and the cluster restores to running status.