Switch over a MySQL cluster

You can initiate a switchover for an ApeCloud MySQL RaftGroup by executing the kbcli or kubectl command. Then KubeBlocks switches the instance roles.

Before you start

• Make sure the cluster is running normally.

• Check whether the following role probe parameters exist to verify whether the role probe is enabled.

  kubectl get cd apecloud-mysql -o yaml
  >
  probes:
    roleProbe:
      failureThreshold: 3
      periodSeconds: 2
      timeoutSeconds: 1

Initiate the switchover

You can switch over a follower of an ApeCloud MySQL RaftGroup to the leader role, and the former leader instance to a follower.

kbcli

• Initiate a switchover with no leader instance specified.

  kbcli cluster promote mycluster

• Initiate a switchover with a specified new leader instance.

  kbcli cluster promote mycluster --instance='mycluster-mysql-2'

• If there are multiple components, you can use --component to specify a component.

  kbcli cluster promote mycluster --instance='mycluster-mysql-2' --component='apecloud-mysql'

kubectl

The value of instanceName decides whether a new leader instance is specified for the switchover.

• Initiate a switchover with no specified leader instance.

  kubectl apply -f -<<EOF
  apiVersion: apps.kubeblocks.io/v1alpha1
  kind: OpsRequest
  metadata:
    name: mycluster-switchover-jhkgl
  spec:
    clusterRef: mycluster
    type: Switchover
    switchover:
    - componentName: apecloud-mysql
      instanceName: '*'
  >>

• Initiate a switchover with a specified new leader instance.

  kubectl apply -f -<<EOF
  apiVersion: apps.kubeblocks.io/v1alpha1
  kind: OpsRequest
  metadata:
    name: mycluster-switchover-jhkgl
  spec:
    clusterRef: mycluster
    type: Switchover
    switchover:
    - componentName: apecloud-mysql
      instanceName: 'mycluster-mysql-2'
  >>

Verify the switchover

Check the instance status to verify whether the switchover is performed successfully.

kbcli cluster list-instances

Handle an exception

If an error occurs, refer to Handle an exception to troubleshoot the operation.