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Hazelcast Volume Expansion

This guide will give an overview on how KubeDB Ops-manager operator expand the volume of Hazelcast cluster members.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • Hazelcast
  • HazelcastOpsRequest

How Volume Expansion Process Works

The following diagram shows how KubeDB Ops-manager operator expand the volumes of Hazelcast 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 Hazelcast Custom Resource (CR).

2. KubeDB Provisioner operator watches the Hazelcast CR.

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

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

5. Then, in order to expand the volume of the Hazelcast database the user creates a HazelcastOpsRequest CR with desired information.

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

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

8. Then the KubeDB Ops-manager operator will expand the related PersistentVolumeClaims to reach the expected size defined in the HazelcastOpsRequest CR.

9. After the successful expansion of the related PersistentVolumeClaims, the KubeDB Ops-manager operator updates the related statefulset so that the new volumes can be mounted.

10. After successfully updating statefulsets, the KubeDB Ops-manager operator resumes the Hazelcast 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 expanding volume of various Hazelcast cluster members using HazelcastOpsRequest CRD.