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ZooKeeper Horizontal Scaling

This guide will give an overview on how KubeDB Ops-manager operator scales up or down ZooKeeper cluster.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • ZooKeeper
  • ZooKeeperOpsRequest

How Horizontal Scaling Process Works

The following diagram shows how KubeDB Ops-manager operator scales up or down ZooKeeper database components. Open the image in a new tab to see the enlarged version.

  

The Horizontal scaling process consists of the following steps:

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

2. KubeDB Provisioner operator watches the ZooKeeper CR.

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

4. Then, in order to scale the ZooKeeper cluster, the user creates a ZooKeeperOpsRequest CR with desired information.

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

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

7. Then the KubeDB Ops-manager operator will scale the related PetSet Pods to reach the expected number of replicas defined in the ZooKeeperOpsRequest CR.

8. After the successfully scaling the replicas of the related PetSet Pods, the KubeDB Ops-manager operator updates the number of replicas in the ZooKeeper object to reflect the updated state.

9. After the successful scaling of the ZooKeeper replicas, the KubeDB Ops-manager operator resumes the ZooKeeper 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 horizontal scaling of ZooKeeper database using ZooKeeperOpsRequest CRD.