Scale for a Redis cluster
You can scale Redis DB instances in two ways, vertical scaling and horizontal scaling.
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
Run the command below to check whether the cluster STATUS is Running
. Otherwise, the following operations may fail.
kbcli cluster list redis-cluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
redis-cluster default redis redis-7.0.6 Delete Running Apr 10,2023 16:21 UTC+0800
Steps
Change configuration.
Configure the parameters
--components
,--memory
, and--cpu
and run the command.kbcli cluster vscale redis-cluster \
--components="redis" \
--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.
Validate the vertical scaling.
Check the cluster status to identify the vertical scaling status.
kbcli cluster list redis-cluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
redis-cluster default redis redis-7.0.6 Delete Updating Apr 10,2023 16:27 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 the normal instances number is less than the total instance number or the leader instance is running properly while others are abnormal.
To solve the problem, you can check manually to see whether resources are sufficient. If AutoScaling is supported, the system recovers when there are enough resources, otherwise, you can create enough resources and check the result with kubectl describe command.
noteVertical scaling does not synchronize parameters related to CPU and memory and it is required to manually call the opsRequest of configuration to change parameters accordingly. Refer to Configuration for instructions.
Check whether the corresponding resources change.
kbcli cluster describe redis-cluster
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 redis-cluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
redis-cluster default redis redis-7.0.6 Delete Running Apr 10,2023 16:50 UTC+0800
Steps
Change configuration.
Configure the parameters
--components
and--replicas
, and run the command.kbcli cluster hscale redis-cluster \
--components="redis" --replicas=2--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 redis-cluster
>
NAME NAMESPACE CLUSTER-DEFINITION VERSION TERMINATION-POLICY STATUS CREATED-TIME
redis-cluster default redis redis-7.0.6 Delete Updating Apr 10,2023 16:58 UTC+0800- STATUS=Updating: it means horizontal scaling is in progress.
- STATUS=Running: it means horizontal scaling has been applied.
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: "2023-04-10T18:20:26Z"
message: VolumeSnapshot/redis-cluster-redis-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. 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=redis-cluster
kubectl delete volumesnapshot -l app.kubernetes.io/instance=redis-cluster
Result
The horizontal scaling continues after the backup and volumesnapshot are deleted and the cluster restores to running status.