Vertical Scaling for ClickHouse

Vertical scaling adjusts the CPU and memory allocated to a component's pods. KubeBlocks performs a rolling restart to apply the new resource limits.

Prerequisites

• A functional Kubernetes cluster (v1.21+ recommended)
• kubectl v1.21+ installed and configured with cluster access
• KubeBlocks installed (installation guide)
• ClickHouse Add-on enabled
• A demo namespace: kubectl create ns demo

Scale the ClickHouse Component

kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: clickhouse-verticalscaling
  namespace: demo
spec:
  clusterName: clickhouse-cluster
  type: VerticalScaling
  verticalScaling:
    - componentName: clickhouse
      requests:
        cpu: "1"
        memory: "2Gi"
      limits:
        cpu: "1"
        memory: "2Gi"
EOF

Monitor progress:

kubectl get opsrequest clickhouse-verticalscaling -n demo -w

NAME                        TYPE              CLUSTER              STATUS    PROGRESS   AGE
clickhouse-verticalscaling  VerticalScaling   clickhouse-cluster   Succeed   1/1        60s

Scale the ClickHouse Keeper Component

For clusters using the cluster topology, scale the Keeper separately:

kubectl apply -f - <<EOF
apiVersion: operations.kubeblocks.io/v1alpha1
kind: OpsRequest
metadata:
  name: clickhouse-verticalscaling-keeper
  namespace: demo
spec:
  clusterName: clickhouse-cluster
  type: VerticalScaling
  verticalScaling:
    - componentName: ch-keeper
      requests:
        cpu: "0.5"
        memory: "1Gi"
      limits:
        cpu: "0.5"
        memory: "1Gi"
EOF

Verify the new resource allocation:

CH_POD=$(kubectl get pods -n demo -l app.kubernetes.io/instance=clickhouse-cluster \
  -l apps.kubeblocks.io/component-name!=ch-keeper \
  -o jsonpath='{.items[0].metadata.name}')
kubectl get pod $CH_POD -n demo \
  -o jsonpath='{.spec.containers[0].resources}' | python3 -m json.tool

Cleanup

kubectl delete opsrequest clickhouse-verticalscaling clickhouse-verticalscaling-keeper -n demo --ignore-not-found