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Using Custom Configuration File

KubeDB supports providing custom configuration for Redis. This tutorial will show you how to use KubeDB to run Redis 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/redis folder in GitHub repository kubedb/docs.

Overview

Redis allows configuration via a config file. When redis docker image starts, it executes redis-server command. If we provide a .conf file directory as an argument of this command, Redis server will use configuration specified in the file. To know more about configuring Redis see here.

At first, you have to create a config file named redis.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 Redis crd. KubeDB will mount this volume into /usr/local/etc/redis directory of the pod and the redis.conf file path will be sent as an argument of redis-server command.

In this tutorial, we will configure databases and maxclients via a custom config file. We will use Secret as volume source.

Custom Configuration

At first, let’s create redis.conf file setting databases and maxclients parameters. Default value of databases is 16 and maxclients is 10000.

$ cat <<EOF >redis.conf
databases 10
maxclients 500
EOF

$ cat redis.conf
databases 10
maxclients 500

Note that config file name must be redis.conf

Now, create a Secret with this configuration file.

$ kubectl create secret generic -n demo rd-configuration --from-file=./redis.conf
secret/rd-configuration created

Verify the Secret has the configuration file.

$ kubectl get secret -n demo rd-configuration -o yaml

apiVersion: v1
stringData:
  redis.conf: |
    databases 10
    maxclients 500    
kind: Secret
metadata:
  name: rd-configuration
  namespace: demo

Now, create Redis crd specifying spec.configSecret field.

$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.12.21/docs/examples/redis/configuration/redis-custom.yaml
redis.kubedb.com "custom-redis" created

Below is the YAML for the Redis crd we just created.

apiVersion: kubedb.com/v1alpha2
kind: Redis
metadata:
  name: custom-redis
  namespace: demo
spec:
  version: 6.0.6
  configSecret:
    name: rd-configuration
  storage:
    storageClassName: "standard"
    accessModes:
    - ReadWriteOnce
    resources:
      requests:
        storage: 1Gi

Now, wait a few minutes. KubeDB operator will create necessary statefulset, services etc. If everything goes well, we will see that a pod with the name custom-redis-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo custom-redis-0
NAME             READY     STATUS    RESTARTS   AGE
custom-redis-0   1/1       Running   0          25s

Check the pod’s log to see if the database is ready

$ kubectl logs -f -n demo custom-redis-0
1:C 01 Oct 08:07:45.274 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
1:C 01 Oct 08:07:45.274 # Redis version=4.0.6, bits=64, commit=00000000, modified=0, pid=1, just started
1:C 01 Oct 08:07:45.274 # Configuration loaded
1:M 01 Oct 08:07:45.275 * Running mode=standalone, port=6379.
1:M 01 Oct 08:07:45.275 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
1:M 01 Oct 08:07:45.275 # Server initialized
1:M 01 Oct 08:07:45.275 * Ready to accept connections

Once we see Ready to accept connections in the log, the database is ready.

Now, we will check if the database has started with the custom configuration we have provided. We will exec into the pod and use CONFIG GET command to check the configuration.

 $ kubectl exec -it -n demo custom-redis-0 sh
/data # redis-cli
127.0.0.1:6379> ping
PONG
127.0.0.1:6379> config get databases
1) "databases"
2) "10"
127.0.0.1:6379> config get maxclients
1) "maxclients"
2) "500"
127.0.0.1:6379> exit
/data #

Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo rd/custom-redis -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo rd/custom-redis

kubectl patch -n demo drmn/custom-redis -p '{"spec":{"wipeOut":true}}' --type="merge"
kubectl delete -n demo drmn/custom-redis

kubectl delete -n demo secret rd-configuration

kubectl delete ns demo

Next Steps

• Learn how to use KubeDB to run a Redis server here.
• Want to hack on KubeDB? Check our contribution guidelines.