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 (e.g. 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.
kubectl get cluster mycluster
>
NAME CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS AGE
mycluster mysql mysql-8.0.33 Delete Running 18m
Steps
There are two ways to apply vertical scaling.
- OpsRequest
- Edit cluster YAML file
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"
EOFCheck 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 6mIf an error occurs, you can troubleshoot with
kubectl describe ops -n demo
command to view the events of this operation.Check whether the corresponding resources change.
kubectl describe cluster mycluster
Change the configuration of
spec.componentSpecs.resources
in the YAML file.spec.componentSpecs.resources
controls the requirement and limit of resources and changing them triggers a vertical scaling.kubectl edit cluster mycluster -n demo
>
apiVersion: apps.kubeblocks.io/v1alpha1
kind: Cluster
metadata:
name: mycluster
namespace: demo
spec:
clusterDefinitionRef: mysql
clusterVersionRef: mysql-8.0.30
componentSpecs:
- name: mysql
componentDefRef: mysql
replicas: 2
resources: # Change the values of resources.
requests:
memory: "2Gi"
cpu: "1"
limits:
memory: "4Gi"
cpu: "2"
volumeClaimTemplates:
- name: data
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 40Gi
terminationPolicy: DeleteCheck whether the corresponding resources change.
kubectl describe cluster 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 for more details and examples.
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 19m
Steps
There are two ways to apply horizontal scaling.
- OpsRequest
- Edit cluster YAML file
Apply an OpsRequest to a specified cluster. Configure the parameters according to your needs.
The example below means adding two replicas.
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
scaleOut:
replicaChanges: 2
EOFIf you want to scale in replicas, replace
scaleOut
withscaleIn
.The example below means deleting two replicas.
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
scaleIn:
replicaChanges: 2
EOFCheck 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 6mIf an error occurs, you can troubleshoot with
kubectl describe ops -n demo
command to view the events of this operation.Check whether the corresponding resources change.
kubectl describe cluster mycluster -n demo
Change the configuration of
spec.componentSpecs.replicas
in the YAML file.spec.componentSpecs.replicas
stands for the pod amount and changing this value triggers a horizontal scaling of a cluster.kubectl edit cluster mycluster -n demo
>
apiVersion: apps.kubeblocks.io/v1alpha1
kind: Cluster
metadata:
name: mycluster
namespace: demo
spec:
clusterDefinitionRef: mysql
clusterVersionRef: mysql-8.0.30
componentSpecs:
- name: mysql
componentDefRef: mysql
replicas: 1 # Change the amount
volumeClaimTemplates:
- name: data
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
terminationPolicy: DeleteCheck 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: "2024-04-28T04:20:26Z"
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.