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Vertical Scaling MSSQLServer

This guide will give you an overview of how KubeDB Ops Manager updates the resources(for example Memory, CPU etc.) of the MSSQLServer.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • MSSQLServer
  • MSSQLServerOpsRequest

How Vertical Scaling Process Works

The following diagram shows how the KubeDB Ops Manager used to update the resources of the MSSQLServer. Open the image in a new tab to see the enlarged version.

  

The vertical scaling process consists of the following steps:

1. At first, a user creates a MSSQLServer CR.

2. KubeDB provisioner operator watches for the MSSQLServer CR.

3. When the operator finds a MSSQLServer CR, it creates a PetSet and related necessary stuff like secret, service, etc.

4. Then, in order to update the resources(for example CPU, Memory etc.) of the MSSQLServer cluster the user creates a MSSQLServerOpsRequest CR with desired information.

5. KubeDB Ops Manager watches for MSSQLServerOpsRequest.

6. When it finds one, it halts the MSSQLServer object so that the KubeDB provisioner operator doesn’t perform any operation on the MSSQLServer during the scaling process.

7. Then the KubeDB Ops-manager operator will update resources of the PetSet’s Pods to reach desired state.

8. After successful updating of the resources of the PetSet’s Pods, the KubeDB Ops Manager updates the MSSQLServer object resources to reflect the updated state.

9. After successful updating of the MSSQLServer resources, the KubeDB Ops Manager resumes the MSSQLServer object so that the KubeDB Provisioner operator resumes its usual operations.

Vertical Scaling Modes

KubeDB actuates vertical scaling in one of two modes, selected through the spec.verticalScaling.mode field of the MSSQLServerOpsRequest:

• Restart (default): The operator patches the PetSet with the new resources and restarts the Pods (one at a time, honoring the database’s failover rules) so they come back with the updated CPU and Memory. This works on every Kubernetes cluster.
• InPlace: The operator resizes the running containers in place using the Kubernetes in-place Pod resize (pods/resize subresource) — no Pod restart, so scaling happens without downtime or failover. If a Node cannot accommodate the new resources (the resize is reported Infeasible), the operator automatically falls back to the Restart behavior for that Pod.

If spec.verticalScaling.mode is omitted, it defaults to Restart.

Note: InPlace mode relies on the Kubernetes InPlacePodVerticalScaling feature gate, which is enabled by default from Kubernetes v1.33. On older clusters, or when the feature gate is disabled, use Restart mode.

In the next doc, we are going to show a step-by-step guide on updating resources of MSSQLServer database using vertical scaling operation.