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Vertical Scale ClickHouse Standalone

This guide will show you how to use KubeDB Ops-manager operator to update the resources of a ClickHouse standalone.

Before You Begin

  • At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.

  • Install KubeDB Provisioner and Ops-manager operator in your cluster following the steps here.

  • You should be familiar with the following KubeDB concepts:

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/clickhouse directory of kubedb/docs repository.

Apply Vertical Scaling on ClickHouse Standalone

Here, we are going to deploy a ClickHouse cluster using a supported version by KubeDB operator. Then we are going to apply vertical scaling on it.

Prepare ClickHouse Standalone

Now, we are going to deploy a ClickHouse cluster database with version 24.4.1.

Deploy ClickHouse Standalone

In this section, we are going to deploy a ClickHouse standalone. Then, in the next section we will update the resources of the database using ClickHouseOpsRequest CRD. Below is the YAML of the ClickHouse CR that we are going to create,

apiVersion: kubedb.com/v1alpha2
kind: ClickHouse
metadata:
  name: clickhouse-prod
  namespace: demo
spec:
  version: 24.4.1
  replicas: 1
  storage:
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 2Gi
  deletionPolicy: WipeOut

Let’s create the ClickHouse CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.8.31/docs/examples/clickhouse/scaling/clickhouse-standalone.yaml
clickhouse.kubedb.com/clickhouse-prod created

Now, wait until clickhouse-prod has status Ready. i.e,

➤ kubectl get clickhouse -n demo -w
NAME              TYPE                  VERSION   STATUS         AGE
clickhouse-prod   kubedb.com/v1alpha2   24.4.1    Provisioning   4s
clickhouse-prod   kubedb.com/v1alpha2   24.4.1    Provisioning   50s
.
.
clickhouse-prod   kubedb.com/v1alpha2   24.4.1    Ready          2m5s

Let’s check the Pod containers resources of the ClickHouse cluster. Run the following command to get the resources of the containers of the ClickHouse cluster

➤ kubectl get pod -n demo clickhouse-prod-0 -o json | jq '.spec.containers[].resources'
{
  "limits": {
    "memory": "4Gi"
  },
  "requests": {
    "cpu": "1",
    "memory": "4Gi"
  }
}

We are now ready to apply the ClickHouseOpsRequest CR to update the resources of this database.

Vertical Scaling

Here, we are going to update the resources of the clickhouse standalone to meet the desired resources after scaling.

Create ClickHouseOpsRequest

In order to update the resources of the database, we have to create a ClickHouseOpsRequest CR with our desired resources. Below is the YAML of the ClickHouseOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: ClickHouseOpsRequest
metadata:
  name: ch-vertical-scale-standalone
  namespace: demo
spec:
  type: VerticalScaling
  databaseRef:
    name: clickhouse-prod
  verticalScaling:
    node:
      resources:
        requests:
          memory: "3Gi"
          cpu: "3"
        limits:
          memory: "3Gi"
          cpu: "3"

Here,

  • spec.databaseRef.name specifies that we are performing vertical scaling operation on clickhouse-prod cluster.
  • spec.type specifies that we are performing VerticalScaling on clickhouse.
  • spec.verticalScaling.standalone specifies the desired resources after scaling.

Let’s create the ClickHouseOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2025.8.31/docs/examples/clickhouse/scaling/vertical-scaling/ch-vertical-ops-standalone.yaml
clickhouseopsrequest.ops.kubedb.com/ch-vertical-scale-standalone created

Verify ClickHouse standalone resources updated successfully

If everything goes well, KubeDB Ops-manager operator will update the resources of ClickHouse object and related PetSets and Pods.

Let’s wait for ClickHouseOpsRequest to be Successful. Run the following command to watch ClickHouseOpsRequest CR,

➤ kubectl get clickhouseopsrequest -n demo ch-vertical-scale-standalone 
NAME                           TYPE              STATUS       AGE
ch-vertical-scale-standalone   VerticalScaling   Successful   68s

We can see from the above output that the ClickHouseOpsRequest has succeeded. If we describe the ClickHouseOpsRequest we will get an overview of the steps that were followed to scale the clickhouse standalone.

➤ kubectl describe clickhouseopsrequest -n demo ch-vertical-scale-standalone 
Name:         ch-vertical-scale-standalone
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         ClickHouseOpsRequest
Metadata:
  Creation Timestamp:  2025-08-26T06:50:05Z
  Generation:          1
  Resource Version:    924257
  UID:                 1556f9bd-3728-4c5c-97cb-12396ab71cfb
Spec:
  Apply:  IfReady
  Database Ref:
    Name:  clickhouse-prod
  Type:    VerticalScaling
  Vertical Scaling:
    Standalone:
      Resources:
        Limits:
          Cpu:     3
          Memory:  3Gi
        Requests:
          Cpu:     3
          Memory:  3Gi
Status:
  Conditions:
    Last Transition Time:  2025-08-26T06:50:05Z
    Message:               ClickHouse ops-request has started to vertically scaling the ClickHouse nodes
    Observed Generation:   1
    Reason:                VerticalScaling
    Status:                True
    Type:                  VerticalScaling
    Last Transition Time:  2025-08-26T06:50:08Z
    Message:               Successfully updated PetSets Resources
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2025-08-26T06:50:33Z
    Message:               Successfully Restarted Pods With Resources
    Observed Generation:   1
    Reason:                RestartPods
    Status:                True
    Type:                  RestartPods
    Last Transition Time:  2025-08-26T06:50:13Z
    Message:               get pod; ConditionStatus:True; PodName:clickhouse-prod-0
    Observed Generation:   1
    Status:                True
    Type:                  GetPod--clickhouse-prod-0
    Last Transition Time:  2025-08-26T06:50:13Z
    Message:               evict pod; ConditionStatus:True; PodName:clickhouse-prod-0
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--clickhouse-prod-0
    Last Transition Time:  2025-08-26T06:50:18Z
    Message:               running pod; ConditionStatus:False
    Observed Generation:   1
    Status:                False
    Type:                  RunningPod
    Last Transition Time:  2025-08-26T06:50:33Z
    Message:               Successfully completed the vertical scaling for ClickHouse
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                                                      Age   From                         Message
  ----     ------                                                      ----  ----                         -------
  Normal   Starting                                                    2m    KubeDB Ops-manager Operator  Start processing for ClickHouseOpsRequest: demo/ch-vertical-scale-standalone
  Normal   Starting                                                    2m    KubeDB Ops-manager Operator  Pausing ClickHouse databse: demo/clickhouse-prod
  Normal   Successful                                                  2m    KubeDB Ops-manager Operator  Successfully paused ClickHouse database: demo/clickhouse-prod for ClickHouseOpsRequest: ch-vertical-scale-standalone
  Normal   UpdatePetSets                                               117s  KubeDB Ops-manager Operator  Successfully updated PetSets Resources
  Warning  get pod; ConditionStatus:True; PodName:clickhouse-prod-0    112s  KubeDB Ops-manager Operator  get pod; ConditionStatus:True; PodName:clickhouse-prod-0
  Warning  evict pod; ConditionStatus:True; PodName:clickhouse-prod-0  112s  KubeDB Ops-manager Operator  evict pod; ConditionStatus:True; PodName:clickhouse-prod-0
  Warning  running pod; ConditionStatus:False                          107s  KubeDB Ops-manager Operator  running pod; ConditionStatus:False
  Normal   RestartPods                                                 92s   KubeDB Ops-manager Operator  Successfully Restarted Pods With Resources
  Normal   Starting                                                    92s   KubeDB Ops-manager Operator  Resuming ClickHouse database: demo/clickhouse-prod
  Normal   Successful                                                  92s   KubeDB Ops-manager Operator  Successfully resumed ClickHouse database: demo/clickhouse-prod for ClickHouseOpsRequest: ch-vertical-scale-standalone

Now, we are going to verify from one of the Pod yaml whether the resources of the clickhouse standalone has updated to meet up the desired state, Let’s check,

➤ kubectl get pod -n demo clickhouse-prod-0 -o json | jq '.spec.containers[].resources'
{
  "limits": {
    "cpu": "3",
    "memory": "3Gi"
  },
  "requests": {
    "cpu": "3",
    "memory": "3Gi"
  }
}

The above output verifies that we have successfully scaled up the resources of the ClickHouse cluster.

Cleaning Up

To clean up the Kubernetes resources created by this tutorial, run:

kubectl delete clickhouse -n demo clickhouse-prod
kubectl delete clickhouseopsrequest -n demo ch-vertical-scale-standalone
kubectl delete ns demo

Next Steps