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Using Custom Configuration File
KubeDB supports providing custom configuration for Memcached. This tutorial will show you how to use KubeDB to run Memcached with custom configuration.
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.
Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.
To keep things isolated, this tutorial uses a separate namespace called
demo
throughout this tutorial.$ kubectl create ns demo namespace/demo created $ kubectl get ns demo NAME STATUS AGE demo Active 5s
Note: YAML files used in this tutorial are stored in docs/examples/memcached folder in GitHub repository kubedb/docs.
Overview
Memcached does not allows to configuration via any file. However, configuration parameters can be set as arguments while starting the memcached docker image. To keep similarity with other KubeDB supported databases which support configuration through a config file, KubeDB has added an additional executable script on top of the official memcached docker image. This script parses the configuration file then set them as arguments of memcached binary.
To know more about configuring Memcached server see here.
At first, you have to create a config file named memcached.conf
with your desired configuration. Then you have to put this file into a volume. You have to specify this volume in spec.configSecret
section while creating Memcached crd. KubeDB will mount this volume into /usr/config
directory of the database pod.
In this tutorial, we will configure max_connections and limit_maxbytes via secret.
Create a secret with custom configuration file:
apiVersion: v1
stringData:
memcached.conf: |
--conn-limit=500
--memory-limit=128
kind: Secret
metadata:
name: mc-configuration
namespace: demo
resourceVersion: "4505"
Here, –con-limit means max simultaneous connections which is default value is 1024. and –memory-limit means item memory in megabytes which default value is 64.
$ kubectl apply -f mc-configuration.yaml
secret/mc-configuration created
Let’s get the mc-configuration secret
with custom configuration:
$ $ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/memcached/custom-config/mc-configuration.yaml
apiVersion: v1
data:
memcached.conf: LS1jb25uLWxpbWl0PTUwMAotLW1lbW9yeS1saW1pdD01MTIK
kind: Secret
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Secret","metadata":{"annotations":{},"name":"mc-configuration","namespace":"demo","resourceVersion":"4505"},"stringData":{"memcached.conf":"--conn-limit=500\n--memory-limit=512\n"}}
creationTimestamp: "2024-08-26T12:19:54Z"
name: mc-configuration
namespace: demo
resourceVersion: "4580860"
uid: 02d41fc0-590e-44d1-ae95-2ee8f9632d36
type: Opaque
Now, create Memcached crd specifying spec.configSecret
field.
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2024.11.18/docs/examples/memcached/configuration/mc-custom.yaml
memcached.kubedb.com/custom-memcached created
Below is the YAML for the Memcached crd we just created.
apiVersion: kubedb.com/v1
kind: Memcached
metadata:
name: custom-memcached
namespace: demo
spec:
replicas: 1
version: "1.6.22"
configSecret:
name: mc-configuration
podTemplate:
spec:
containers:
- name: memcached
resources:
limits:
cpu: 500m
memory: 128Mi
requests:
cpu: 250m
memory: 64Mi
deletionPolicy: WipeOut
Now, wait a few minutes. KubeDB operator will create necessary petset, services etc. If everything goes well, we will see that a pod with the name custom-memcached-0
has been created.
Check if the database is ready
$ kubectl get mc -n demo
NAME VERSION STATUS AGE
custom-memcached 1.6.22 Ready 17m
Now, we will check if the database has started with the custom configuration we have provided. We will use stats command to check the configuration.
We will connect to custom-memcached-0
pod from local-machine using port-frowarding.
$ kubectl port-forward -n demo custom-memcached-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
...
STAT limit_maxbytes 134217728
...
END
Here, limit_maxbytes
is represented in bytes.
Cleaning up
To cleanup the Kubernetes resources created by this tutorial, run:
kubectl patch -n demo mc/custom-memcached -p '{"spec":{"deletionPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo mc/custom-memcached
kubectl patch -n demo drmn/custom-memcached -p '{"spec":{"wipeOut":true}}' --type="merge"
kubectl delete -n demo drmn/custom-memcached
kubectl delete -n demo secret mc-configuration
kubectl delete ns demo
If you would like to uninstall KubeDB operator, please follow the steps here.
Next Steps
- Learn how to use KubeDB to run a Memcached server here.
- Want to hack on KubeDB? Check our contribution guidelines.