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Vertical Scaling Postgres

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

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • Postgres
  • PostgresOpsRequest

How Vertical Scaling Process Works

The following diagram shows how the KubeDB Ops Manager used to update the resources of the Postgres database server. 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 Postgres cr.

2. KubeDB community operator watches for the Postgres cr.

3. When it finds one, 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 Postgres database the user creates a PostgresOpsRequest cr.

5. KubeDB Ops Manager watches for PostgresOpsRequest.

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

7. Then the KubeDB Ops Manager operator will update resources of the PetSet replicas to reach the desired state.

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

9. After successful updating of the Postgres resources, the KubeDB Ops Manager resumes the Postgres 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 PostgresOpsRequest:

• 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. For a distributed Postgres deployment, in-place resize is not possible, so InPlace automatically degrades to Restart.

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 Postgres database using vertical scaling operation.