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ClickHouse Vertical Autoscaling

This guide will give an overview on how KubeDB Autoscaler operator autoscales the database storage using ClickHouseAutoscaler crd.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • ClickHouse
  • ClickHouseAutoscaler
  • ClickHouseOpsRequest

How Storage Autoscaling Works

  

The following diagram shows how KubeDB Autoscaler operator autoscales the resources of ClickHouse database components. Open the image in a new tab to see the enlarged version.

The Auto Scaling process consists of the following steps:

1. At first, a user creates a ClickHouse Custom Resource (CR).

2. KubeDB Provisioner operator watches the ClickHouse CR.

3. When the operator finds a ClickHouse CR, it creates required number of StatefulSets and related necessary stuff like secrets, services, etc.

• Each StatefulSet creates a Persistent Volume according to the Volume Claim Template provided in the statefulset configuration.

4. Then, in order to set up storage autoscaling of the ClickHouse cluster, the user creates a ClickHouseAutoscaler CRO with desired configuration.

5. KubeDB Autoscaler operator watches the ClickHouseAutoscaler CRO.

6. KubeDB Autoscaler operator continuously watches persistent volumes of the databases to check if it exceeds the specified usage threshold.

• If the usage exceeds the specified usage threshold, then KubeDB Autoscaler operator creates a ClickHouseOpsRequest to expand the storage of the database.

7. KubeDB Ops-manager operator watches the ClickHouseOpsRequest CRO.

8. Then the KubeDB Ops-manager operator will expand the storage of the database component as specified on the ClickHouseOpsRequest CRO.

In the next docs, we are going to show a step by step guide on Autoscaling storage of various ClickHouse database components using ClickHouseAutoscaler CRD.