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Reconfiguring ClickHouse

This guide will give an overview on how KubeDB Ops-manager operator reconfigures ClickHouse cluster.

Before You Begin

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

How Reconfiguring ClickHouse Process Works

The following diagram shows how KubeDB Ops-manager operator reconfigures ClickHouse components. Open the image in a new tab to see the enlarged version.

  

The Reconfiguring ClickHouse 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 PetSets and related necessary stuff like secrets, services, etc.

4. Then, in order to reconfigure the ClickHouse database the user creates a ClickHouseOpsRequest CR with desired information.

5. KubeDB Ops-manager operator watches the ClickHouseOpsRequest CR.

6. When it finds a ClickHouseOpsRequest CR, it halts the ClickHouse object which is referred from the ClickHouseOpsRequest. So, the KubeDB Provisioner operator doesn’t perform any operations on the ClickHouse object during the reconfiguring process.

7. Then the KubeDB Ops-manager operator will replace the existing configuration with the new configuration provided or merge the new configuration with the existing configuration according to the ClickHouseOpsRequest CR.

8. Then the KubeDB Ops-manager operator will restart the related PetSet Pods so that they restart with the new configuration defined in the ClickHouseOpsRequest CR.

9. After the successful reconfiguring of the ClickHouse components, the KubeDB Ops-manager operator resumes the ClickHouse object so that the KubeDB Provisioner operator resumes its usual operations.

In the next docs, we are going to show a step by step guide on reconfiguring ClickHouse components using ClickHouseOpsRequest CRD.