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Reconfigure Memcached Database

This guide will show you how to use KubeDB Ops-manager operator to reconfigure a Memcached database.

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.
Install KubeDB Provisioner and Ops-manager operator in your cluster following the steps here.
You should be familiar with the following KubeDB concepts:

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.

Now, we are going to deploy a Memcached database using a supported version by KubeDB operator. Then we are going to apply MemcachedOpsRequest to reconfigure its configuration.

Prepare Memcached Database

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

Deploy Memcached

At first, we will create secret named mc-configuration containing required configuration settings.

apiVersion: v1
stringData:
  memcached.conf: |
    --conn-limit=500    
kind: Secret
metadata:
  name: mc-configuration
  namespace: demo
  resourceVersion: "4505"

Here, maxclients is set to 500, whereas the default value is 1024.

Now, we will apply the secret with custom configuration.

$ kubectl create -f mc-configuration
secret/mc-configuration created

In this section, we are going to create a Memcached object specifying spec.configSecret field to apply this custom configuration. Below is the YAML of the Memcahced CR that we are going to create,

apiVersion: kubedb.com/v1
kind: Memcached
metadata:
  name: memcd-quickstart
  namespace: demo
spec:
  replicas: 1
  version: "1.6.22"
  configSecret:
    name: mc-configuration
  deletionPolicy: WipeOut

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

$ kubectl create -f https://github.com/kubedb/docs/raw/v2025.2.6-rc.0/docs/examples/memcached/reconfigure/sample-memcached-config.yaml
memcached.kubedb.com/memcd-quickstart created

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

$ kubectl get mc -n demo
NAME               VERSION     STATUS    AGE
memcd-quickstart   1.6.22      Ready     23s

Now, we will check if the database has started with the custom configuration we have provided.

We will connect to memcd-quickstart-0 pod from local-machine using port-frowarding.

$ kubectl port-forward -n demo memcd-quickstart-0 11211
Forwarding from 127.0.0.1:11211 -> 11211
Forwarding from [::1]:11211 -> 11211

Now, connect to the memcached server from a different terminal through telnet.

$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
stats
...
STAT max_connections 500
...
END

As we can see from the configuration of running memcached, the value of maxclients has been set to 500.

Reconfigure using new secret

Now we will reconfigure this database to set maxclients to 2000.

At first, we will create secret named new-configuration containing required configuration settings.

apiVersion: v1
stringData:
  memcached.conf: |
    --conn-limit=2000    
kind: Secret
metadata:
  name: new-configuration
  namespace: demo
  resourceVersion: "4505"

Here, maxclients is set to 2000.

Now, we will apply the secret with custom configuration.

$ kubectl create -f new-configuration
secret/new-configuration created

Create MemcachedOpsRequest

Now, we will use this secret to replace the previous secret using a MemcachedOpsRequest CR. The MemcachedOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: MemcachedOpsRequest
metadata:
  name: memcd-reconfig
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: memcd-quickstart
  configuration:
    configSecret:
      name: new-configuration

Here,

spec.databaseRef.name specifies that we are reconfiguring memcd-quickstart database.
spec.type specifies that we are performing Reconfigure on our database.
spec.configuration.configSecret.name specifies the name of the new secret.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2025.2.6-rc.0/docs/examples/memcached/reconfigure/ops-request-reconfigure.yaml
memcachedopsrequest.ops.kubedb.com/memcd-reconfig created

Verify the new configuration is working

If everything goes well, KubeDB Ops-manager operator will update the configSecret of Memcached object.

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

$ watch kubectl get memcahcedopsrequest -n demo
Every 2.0s: kubectl get memcachedopsrequest -n demo
NAME                          TYPE          STATUS       AGE
memcd-reconfig                Reconfigure   Successful   1m

We can see from the above output that the MemcachedOpsRequest has succeeded. If we describe the MemcachedOpsRequest we will get an overview of the steps that were followed to reconfigure the database.

$ kubectl describe memcachedopsrequest -n demo memcd-reconfig
Name:         memcd-reconfig
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MemcachedOpsRequest
Metadata:
  Creation Timestamp:  2024-09-02T11:59:59Z
  Generation:          1
  Resource Version:    166566
  UID:                 bb4a1057-ccfa-49c9-8d07-e03cb631a0c9
Spec:
  Apply:  IfReady
  Configuration:
    Config Secret:
      Name:  new-configuration
  Database Ref:
    Name:  memcd-quickstart
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2024-09-02T11:59:59Z
    Message:               Memcached ops request is reconfiguring the cluster
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2024-09-02T12:00:02Z
    Message:               reconfiguring memcached
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2024-09-02T12:00:07Z
    Message:               evict pod; ConditionStatus:True; PodName:memcd-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--memcd-quickstart-0
    Last Transition Time:  2024-09-02T12:00:07Z
    Message:               is pod ready; ConditionStatus:False
    Observed Generation:   1
    Status:                False
    Type:                  IsPodReady
    Last Transition Time:  2024-09-02T12:00:12Z
    Message:               is pod ready; ConditionStatus:True; PodName:memcd-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  IsPodReady--memcd-quickstart-0
    Last Transition Time:  2024-09-02T12:00:12Z
    Message:               Restarted pods after reconfiguration
    Observed Generation:   1
    Reason:                RestartPods
    Status:                True
    Type:                  RestartPods
    Last Transition Time:  2024-09-02T12:00:13Z
    Message:               Successfully completed the modification process.
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason                                                          Age   From                         Message
  ----     ------                                                          ----  ----                         -------
  Normal   PauseDatabase                                                   51s   KubeDB Ops-manager Operator  Pausing Memcached demo/memcd-quickstart
  Normal   RestartPods                                                     38s   KubeDB Ops-manager Operator  Restarted pods after reconfiguration
  Normal   ResumeDatabase                                                  38s   KubeDB Ops-manager Operator  Resuming Memcached demo/memcd-quickstart
  Normal   ResumeDatabase                                                  38s   KubeDB Ops-manager Operator  Successfully resumed Memcached demo/memcd-quickstart
  Normal   Successful                                                      38s   KubeDB Ops-manager Operator  Successfully Reconfigured Database

Now need to check the new configuration we have provided.

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

$ kubectl get mc -n demo
NAME               VERSION     STATUS    AGE
memcd-quickstart   1.6.22      Ready     20s

Now, we will check if the database has started with the custom configuration we have provided.

We will connect to memcd-quickstart-0 pod from local-machine using port-frowarding.

$ kubectl port-forward -n demo memcd-quickstart-0 11211
Forwarding from 127.0.0.1:11211 -> 11211
Forwarding from [::1]:11211 -> 11211

Now, connect to the memcached server from a different terminal through telnet.

$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
stats
...
STAT max_connections 2000
...
END

As we can see from the configuration of running memcached, the value of maxclients has been updated to 2000.

As we can see from the configuration of running memcached, the value of maxclients has been changed from 500 to 2000. So, the reconfiguration of the database is successful.

Reconfigure using apply config

Now we will reconfigure this database again to set maxclients to 3000. This time we won’t use a new secret. We will use the applyConfig field of the MemcachedOpsRequest. This will merge the new config in the existing secret.

Create MemcachedOpsRequest

Now, we will use the new configuration in the data field in the MemcahcedOpsRequest CR. The MemcachedOpsRequest yaml is given below,

apiVersion: ops.kubedb.com/v1alpha1
kind: MemcachedOpsRequest
metadata:
  name: memcd-reconfig
  namespace: demo
spec:
  type: Reconfigure
  databaseRef:
    name: memcd-quickstart
  configuration:
    applyConfig:
      memcached.conf: |
        --conn-limit=3000

Here,

spec.databaseRef.name specifies that we are reconfiguring memcd-quickstart database.
spec.type specifies that we are performing Reconfigure on our database.
spec.configuration.applyConfig specifies the new configuration that will be merged in the existing secret.

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

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2025.2.6-rc.0/docs/examples/memcached/reconfigure/ops-request-reconfigure.yaml
memcachedopsrequest.ops.kubedb.com/memcd-reconfig created

Verify the new configuration is working

If everything goes well, KubeDB Ops-manager operator will merge this new config with the existing configuration.

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

$ watch kubectl get memcachedopsrequest -n demo
Every 2.0s: kubectl get memcachedopsrequest -n demo
NAME                   TYPE          STATUS       AGE
memcd-apply-reconfig   Reconfigure   Successful   38s

We can see from the above output that the MemcachedOpsRequest has succeeded. If we describe the MemcahcedOpsRequest we will get an overview of the steps that were followed to reconfigure the database.

$ kubectl describe memcachedopsrequest -n demo memcd-apply-reconfig
Name:         memcd-apply-reconfig
Namespace:    demo
Labels:       <none>
Annotations:  <none>
API Version:  ops.kubedb.com/v1alpha1
Kind:         MemcachedOpsRequest
Metadata:
  Creation Timestamp:  2024-09-03T06:02:41Z
  Generation:          1
  Resource Version:    178039
  UID:                 d1f90151-abeb-4035-87f4-e2bc89c35b89
Spec:
  Apply:  IfReady
  Configuration:
    Apply Config:
      memcached.conf:  --conn-limit=3000

  Database Ref:
    Name:  memcd-quickstart
  Type:    Reconfigure
Status:
  Conditions:
    Last Transition Time:  2024-09-03T06:02:41Z
    Message:               Memcached ops request is reconfiguring the cluster
    Observed Generation:   1
    Reason:                Reconfigure
    Status:                True
    Type:                  Reconfigure
    Last Transition Time:  2024-09-03T06:02:44Z
    Message:               reconfiguring memcached
    Observed Generation:   1
    Reason:                UpdatePetSets
    Status:                True
    Type:                  UpdatePetSets
    Last Transition Time:  2024-09-03T06:02:49Z
    Message:               evict pod; ConditionStatus:True; PodName:memcd-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  EvictPod--memcd-quickstart-0
    Last Transition Time:  2024-09-03T06:02:49Z
    Message:               is pod ready; ConditionStatus:False
    Observed Generation:   1
    Status:                False
    Type:                  IsPodReady
    Last Transition Time:  2024-09-03T06:02:54Z
    Message:               is pod ready; ConditionStatus:True; PodName:memcd-quickstart-0
    Observed Generation:   1
    Status:                True
    Type:                  IsPodReady--memcd-quickstart-0
    Last Transition Time:  2024-09-03T06:02:54Z
    Message:               Restarted pods after reconfiguration
    Observed Generation:   1
    Reason:                RestartPods
    Status:                True
    Type:                  RestartPods
    Last Transition Time:  2024-09-03T06:02:54Z
    Message:               Successfully completed the modification process.
    Observed Generation:   1
    Reason:                Successful
    Status:                True
    Type:                  Successful
  Observed Generation:     1
  Phase:                   Successful
Events:
  Type     Reason            Age   From                         Message
  ----     ------            ----  ----                         -------
  Normal   PauseDatabase     26s   KubeDB Ops-manager Operator  Pausing Memcached demo/memcd-quickstart
  Normal   RestartPods       13s   KubeDB Ops-manager Operator  Restarted pods after reconfiguration
  Normal   ResumeDatabase    13s   KubeDB Ops-manager Operator  Resuming Memcached demo/memcd-quickstart
  Normal   ResumeDatabase    13s   KubeDB Ops-manager Operator  Successfully resumed Memcached demo/memcd-quickstart
  Normal   Successful        13s   KubeDB Ops-manager Operator  Successfully Reconfigured Database

Now let’s check the new configuration we have provided.

We will connect to memcd-quickstart-0 pod from local-machine using port-frowarding.

$ kubectl port-forward -n demo memcd-quickstart-0 11211
Forwarding from 127.0.0.1:11211 -> 11211
Forwarding from [::1]:11211 -> 11211

Now, connect to the memcached server from a different terminal through telnet.

$ telnet 127.0.0.1 11211
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
stats
...
STAT max_connections 3000
...
END

As we can see from the configuration of running memcached, the value of maxclients has been changed from 2000 to 3000. So, the reconfiguration of the database using the applyConfig field is successful.

Cleaning Up

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

kubectl delete mc -n demo memcd-quickstart
kubectl delete memcachedopsrequest -n demo memcd-reconfig memcd-apply-reconfig

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Reconfigure Memcached Database

Before You Begin

Prepare Memcached Database

Deploy Memcached

Reconfigure using new secret

Create MemcachedOpsRequest

Verify the new configuration is working

Reconfigure using apply config

Create MemcachedOpsRequest

Verify the new configuration is working

Cleaning Up

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