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Configuring Redis using a ConfigMap

This page provides a real world example of how to configure Redis using a ConfigMap and builds upon the Configure Containers Using a ConfigMap task.

Objectives

  • Create a kustomization.yaml file containing:
    • a ConfigMap generator
    • a Pod resource config using the ConfigMap
  • Apply the directory by running kubectl apply -k ./
  • Verify that the configuration was correctly applied.

Before you begin

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 Minikube, or you can use one of these Kubernetes playgrounds:

To check the version, enter kubectl version.

Real World Example: Configuring Redis using a ConfigMap

You can follow the steps below to configure a Redis cache using data stored in a ConfigMap.

First create a kustomization.yaml containing a ConfigMap from the redis-config file:

pods/config/redis-config 
maxmemory 2mb
maxmemory-policy allkeys-lru

curl -OL https://k8s.io/examples/pods/config/redis-config

cat <<EOF >./kustomization.yaml
configMapGenerator:
- name: example-redis-config
  files:
  - redis-config
EOF

Add the pod resource config to the kustomization.yaml:

pods/config/redis-pod.yaml 
apiVersion: v1
kind: Pod
metadata:
  name: redis
spec:
  containers:
  - name: redis
    image: redis:5.0.4
    command:
      - redis-server
      - "/redis-master/redis.conf"
    env:
    - name: MASTER
      value: "true"
    ports:
    - containerPort: 6379
    resources:
      limits:
        cpu: "0.1"
    volumeMounts:
    - mountPath: /redis-master-data
      name: data
    - mountPath: /redis-master
      name: config
  volumes:
    - name: data
      emptyDir: {}
    - name: config
      configMap:
        name: example-redis-config
        items:
        - key: redis-config
          path: redis.conf

curl -OL https://raw.githubusercontent.com/kubernetes/website/master/content/en/examples/pods/config/redis-pod.yaml

cat <<EOF >>./kustomization.yaml
resources:
- redis-pod.yaml
EOF

Apply the kustomization directory to create both the ConfigMap and Pod objects:

kubectl apply -k .

Examine the created objects by

> kubectl get -k .
NAME                                        DATA   AGE
configmap/example-redis-config-dgh9dg555m   1      52s

NAME        READY   STATUS    RESTARTS   AGE
pod/redis   1/1     Running   0          52s

In the example, the config volume is mounted at /redis-master. It uses path to add the redis-config key to a file named redis.conf. The file path for the redis config, therefore, is /redis-master/redis.conf. This is where the image will look for the config file for the redis master.

Use kubectl exec to enter the pod and run the redis-cli tool to verify that the configuration was correctly applied:

kubectl exec -it redis redis-cli
127.0.0.1:6379> CONFIG GET maxmemory
1) "maxmemory"
2) "2097152"
127.0.0.1:6379> CONFIG GET maxmemory-policy
1) "maxmemory-policy"
2) "allkeys-lru"

Delete the created pod:

kubectl delete pod redis

What's next