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Horizontal Scale Memcached

This guide will give an overview on how KubeDB Ops-manager operator scales up or down Memcached database replicas.

Before You Begin

• At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.

• Install KubeDB Community and Enterprise operator in your cluster following the steps here.

• You should be familiar with the following KubeDB concepts:

  • Memcached
  • MemcachedOpsRequest
  • Horizontal Scaling Overview

To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.

$ kubectl create ns demo
namespace/demo created

Note: YAML files used in this tutorial are stored in docs/examples/memcached directory of kubedb/docs repository.

Apply Horizontal Scaling on Memcached

Here, we are going to deploy a Memcached database using a supported version by KubeDB operator. Then we are going to apply horizontal scaling on it.

Prepare Memcached Database

Now, we are going to deploy a Memcached database with version 1.6.22.

Deploy Memcached Database

In this section, we are going to deploy a Memcached database. Then, in the next section we will update the resources of the database using MemcachedOpsRequest CRD. Below is the YAML of the Memcached CR that we are going to create,

apiVersion: kubedb.com/v1
kind: Memcached
metadata:
  name: memcd-quickstart
  namespace: demo
spec:
  replicas: 3
  version: "1.6.22"
  podTemplate:
    spec:
      containers:
        - name: memcached
          resources:
            limits:
              cpu: 500m
              memory: 128Mi
            requests:
              cpu: 250m
              memory: 64Mi
  deletionPolicy: WipeOut

Let’s create the Memcached CR we have shown above,

$ kubectl create -f https://github.com/kubedb/docs/raw/v2024.11.8-rc.0/docs/examples/memcached/scaling/memcached-horizontal.yaml
memcached.kubedb.com/memcd-quickstart created

Now, wait until memcd-quickstart has status Ready. i.e. ,

$ kubectl get memcached -n demo
NAME               VERSION   STATUS   AGE
memcd-quickstart   1.6.22    Ready    5m

Let’s check the number of replicas this database has from the Memcached object

$ kubectl get memcached -n demo memcd-quickstart -o json | jq '.spec.replicas'
3

We are now ready to apply the MemcachedOpsRequest CR to update the resources of this database.

Horizontal Scaling

Here, we are going to scale up the replicas of the memcached database to meet the desired resources after scaling.

Create MemcachedOpsRequest

In order to scale up the replicas of the memcached database, we have to create a MemcachedOpsRequest CR with our desired number of replicas. Below is the YAML of the MemcachedOpsRequest CR that we are going to create,

apiVersion: ops.kubedb.com/v1alpha1
kind: MemcachedOpsRequest
metadata:
  name: memcd-horizontal-up
  namespace: demo
spec:
  type: HorizontalScaling
  databaseRef:
    name: memcd-quickstart
  horizontalScaling:
    replicas: 5

Here,

• spec.databaseRef.name specifies that we are performing horizontal scaling operation on memcd-quickstart database.
• spec.type specifies that we are performing HorizontalScaling on our database.
• spec.horizontalScaling.replicas specifies the desired number of replicas after scaling.

Let’s create the MemcachedOpsRequest CR we have shown above,

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.8-rc.0/docs/examples/memcached/scaling/horizontal-scaling.yaml
memcachedopsrequest.ops.kubedb.com/memcd-horizontal-up created

Verify Memcached resources updated successfully

If everything goes well, KubeDB Enterprise operator will update the replicas of Memcached object and related PetSets.

Let’s wait for MemcachedOpsRequest to be Successful. Run the following command to watch MemcachedOpsRequest CR,

$ watch kubectl get memcachedopsrequest -n demo memcd-horizontal-up
NAME                  TYPE                STATUS       AGE
memcd-horizontal-up   HorizontalScaling   Successful   3m

Now, we are going to verify if the number of replicas the memcached database has updated to meet up the desired state, Let’s check,

$ kubectl get memcached -n demo memcd-quickstart -o json | jq '.spec.replicas'
5

The above output verifies that we have successfully scaled up the replicas of the Memcached database.

Cleaning up

To clean up the Kubernetes resources created by this tutorial, run:

$ kubectl patch -n demo mc/memcd-quickstart -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
memcached.kubedb.com/memcd-quickstart patched

$ kubectl delete -n demo memcached memcd-quickstart
memcached.kubedb.com "memcd-quickstart" deleted

$ kubectl delete -n demo memcachedopsrequest memcd-horizontal-up 
memcachedopsrequest.ops.kubedb.com "memcd-horizontal-up" deleted