Scale for a MySQL cluster
You can scale a MySQL cluster in two ways, vertical scaling and horizontal scaling.
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, you can change the resource class from 1C2G to 2C4G by performing vertical scaling.
Before you start
Check whether the cluster status is Running
. Otherwise, the following operations may fail.
kbcli cluster list mycluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
mycluster default mysql mysql-8.0.33 Delete Running Jul 05,2024 19:06 UTC+0800
Steps
Change configuration.
Configure the parameters
--components
,--memory
, and--cpu
and run the command.kbcli cluster vscale mycluster \
--components="mysql" \
--memory="4Gi" --cpu="2" \--components
describes the component name ready for vertical scaling.--memory
describes the requested and limited size of the component memory.--cpu
describes the requested and limited size of the component CPU.
Check the cluster status to validate the vertical scaling.
kbcli cluster list mycluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
mycluster default mysql mysql-8.0.33 Delete Updating Jul 05,2024 19:11 UTC+0800STATUS=Updating: it means the vertical scaling is in progress.
STATUS=Running: it means the vertical scaling operation has been applied.
STATUS=Abnormal: it means the vertical scaling is abnormal. The reason may be that the number of the normal instances is less than that of the total instance or the leader instance is running properly while others are abnormal.
To solve the problem, you can manually check whether this error is caused by insufficient resources. Then if AutoScaling is supported by the Kubernetes cluster, the system recovers when there are enough resources. Otherwise, you can create enough resources and troubleshoot with
kubectl describe
command.
Check whether the corresponding resources change.
kbcli cluster describe mycluster
Horizontal scaling
Horizontal scaling changes the amount of pods. For example, you can scale out replicas from three to five.
From v0.9.0, besides replicas, KubeBlocks also supports scaling in and out instances, refer to Horizontal Scale in API docs for more details and examples.
Before you start
Check whether the cluster STATUS is Running
. Otherwise, the following operations may fail.
kbcli cluster list mycluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
mycluster default mysql mysql-8.0.33 Delete Running Jul 05,2024 18:46 UTC+0800
Steps
Change configuration.
Configure the parameters
--components
and--replicas
, and run the command.kbcli cluster hscale mycluster \
--components="mysql" --replicas=3--components
describes the component name ready for horizontal scaling.--replicas
describes the replica amount of the specified components. Edit the amount based on your demands to scale in or out replicas.
Validate the horizontal scaling operation.
Check the cluster STATUS to identify the horizontal scaling status.
kbcli cluster list mycluster
- STATUS=Updating: it means horizontal scaling is in progress.
- STATUS=Running: it means horizontal scaling has been applied.
Check whether the corresponding resources change.
kbcli cluster describe mycluster
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: "2024-07-05T04:20:26Z"
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:
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
EOFDelete 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.