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Memcached Vertical Scaling Overview

This guide will give you an overview on how KubeDB Ops Manager updates the resources(CPU and Memory) of the Memcached database.

Before You Begin

• You should be familiar with the following KubeDB concepts:
  • Memcached
  • MemcachedOpsRequest

How Vertical Scaling Process Works

The following diagram shows how KubeDB Ops Manager updates the resources of the Memcached database. Open the image in a new tab to see the enlarged version.

  

The updating process consists of the following steps:

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

2. KubeDB Community operator watches the Memcached CR.

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

4. Then, in order to update the version of the Memcached database the user creates a MemcachedOpsRequest CR with the desired version.

5. KubeDB Enterprise operator watches the MemcachedOpsRequest CR.

6. When it finds a MemcachedOpsRequest CR, it halts the Memcached object which is referred from the MemcachedOpsRequest. So, the KubeDB Community operator doesn’t perform any operations on the Memcached object during the updating process.

7. After the successful update of the resources of the PetSet’s replica, the KubeDB Enterprise operator updates the Memcached object to reflect the updated state.

8. After successfully updating of Memcachedobject, the KubeDB Enterprise operator resumes the Memcached object so that the KubeDB Community operator can resume its usual operations.

Vertical Scaling Modes

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

• 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 of a Memcached database using update operation.