# Configuring Redis using a ConfigMap

Configuring Redis using a ConfigMapThis page provides a real world example of how to configure Redis using a ConfigMap and builds upon the Configure a Pod to Use a ConfigMap task.ObjectivesCreate a ConfigMap with Redis configuration valuesCreate a Redis Pod that mounts and uses the created ConfigMapVerify that the configuration was correctly applied.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesTo check the version, enter kubectl version.The example shown on this page works with kubectl 1.14 and above.Understand Configure a Pod to Use a ConfigMap.Real World Example: Configuring Redis using a ConfigMapFollow the steps below to configure a Redis cache using data stored in a ConfigMap.First create a ConfigMap with an empty configuration block:cat <<EOF >./example-redis-config.yaml apiVersion: v1 kind: ConfigMap metadata: name: example-redis-config data: redis-config: "" EOF Apply the ConfigMap created above, along with a Redis pod manifest:kubectl apply -f example-redis-config.yaml kubectl apply -f https://raw.githubusercontent.com/kubernetes/website/main/content/en/examples/pods/config/redis-pod.yaml Examine the contents of the Redis pod manifest and note the following:A volume named config is created by spec.volumes[1]The key and path under spec.volumes[1].configMap.items[0] exposes the redis-config key from the example-redis-config ConfigMap as a file named redis.conf on the config volume.The config volume is then mounted at /redis-master by spec.containers[0].volumeMounts[1].This has the net effect of exposing the data in data.redis-config from the example-redis-config ConfigMap above as /redis-master/redis.conf inside the Pod.pods/config/redis-pod.yaml apiVersion: v1 kind: Pod metadata: name: redis spec: containers: - name: redis image: redis:8.0.2 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 Examine the created objects:kubectl get pod/redis configmap/example-redis-config You should see the following output:NAME READY STATUS RESTARTS AGE pod/redis 1/1 Running 0 8s NAME DATA AGE configmap/example-redis-config 1 14s Recall that we left redis-config key in the example-redis-config ConfigMap blank:kubectl describe configmap/example-redis-config You should see an empty redis-config key:Name: example-redis-config Namespace: default Labels: <none> Annotations: <none> Data ==== redis-config: Use kubectl exec to enter the pod and run the redis-cli tool to check the current configuration:kubectl exec -it redis -- redis-cli Check maxmemory:127.0.0.1:6379> CONFIG GET maxmemory It should show the default value of 0:1) "maxmemory" 2) "0" Similarly, check maxmemory-policy:127.0.0.1:6379> CONFIG GET maxmemory-policy Which should also yield its default value of noeviction:1) "maxmemory-policy" 2) "noeviction" Now let's add some configuration values to the example-redis-config ConfigMap:pods/config/example-redis-config.yaml apiVersion: v1 kind: ConfigMap metadata: name: example-redis-config data: redis-config: | maxmemory 2mb maxmemory-policy allkeys-lru Apply the updated ConfigMap:kubectl apply -f example-redis-config.yaml Confirm that the ConfigMap was updated:kubectl describe configmap/example-redis-config You should see the configuration values we just added:Name: example-redis-config Namespace: default Labels: <none> Annotations: <none> Data ==== redis-config: ---- maxmemory 2mb maxmemory-policy allkeys-lru Check the Redis Pod again using redis-cli via kubectl exec to see if the configuration was applied:kubectl exec -it redis -- redis-cli Check maxmemory:127.0.0.1:6379> CONFIG GET maxmemory It remains at the default value of 0:1) "maxmemory" 2) "0" Similarly, maxmemory-policy remains at the noeviction default setting:127.0.0.1:6379> CONFIG GET maxmemory-policy Returns:1) "maxmemory-policy" 2) "noeviction" The configuration values have not changed because the Pod needs to be restarted to grab updated values from associated ConfigMaps. Let's delete and recreate the Pod:kubectl delete pod redis kubectl apply -f https://raw.githubusercontent.com/kubernetes/website/main/content/en/examples/pods/config/redis-pod.yaml Now re-check the configuration values one last time:kubectl exec -it redis -- redis-cli Check maxmemory:127.0.0.1:6379> CONFIG GET maxmemory It should now return the updated value of 2097152:1) "maxmemory" 2) "2097152" Similarly, maxmemory-policy has also been updated:127.0.0.1:6379> CONFIG GET maxmemory-policy It now reflects the desired value of allkeys-lru:1) "maxmemory-policy" 2) "allkeys-lru" Clean up your work by deleting the created resources:kubectl delete pod/redis configmap/example-redis-config What's nextLearn more about ConfigMaps.Follow an example of Updating configuration via a ConfigMap.