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Druid Volume Expansion

This guide will give an overview on how KubeDB Ops-manager operator expand the volume of various component of Druid like:. (Combined and Topology).

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • Druid
  • DruidOpsRequest

How Volume Expansion Process Works

The following diagram shows how KubeDB Ops-manager operator expand the volumes of Druid database components. Open the image in a new tab to see the enlarged version.

  

The Volume Expansion process consists of the following steps:

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

2. KubeDB Provisioner operator watches the Druid CR.

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

4. Each PetSet creates a Persistent Volume according to the Volume Claim Template provided in the petset configuration. This Persistent Volume will be expanded by the KubeDB Ops-manager operator.

5. Then, in order to expand the volume of the druid data components (ie. Historicals, MiddleManagers) of the Druid, the user creates a DruidOpsRequest CR with desired information.

6. KubeDB Ops-manager operator watches the DruidOpsRequest CR.

7. When it finds a DruidOpsRequest CR, it halts the Druid object which is referred from the DruidOpsRequest. So, the KubeDB Provisioner operator doesn’t perform any operations on the Druid object during the volume expansion process.

8. Then the KubeDB Ops-manager operator will expand the persistent volume to reach the expected size defined in the DruidOpsRequest CR.

9. After the successful Volume Expansion of the related PetSet Pods, the KubeDB Ops-manager operator updates the new volume size in the Druid object to reflect the updated state.

10. After the successful Volume Expansion of the Druid components, the KubeDB Ops-manager operator resumes the Druid 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 Volume Expansion of various Druid database components using DruidOpsRequest CRD.