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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 Using ConfigMap Data in Pods and Configure Containers Using a ConfigMap tasks.

• Objectives
• Before you begin
• Real World Example: Configuring Redis using a ConfigMap
• What’s next

Objectives

• Create a ConfigMap.
• Create a pod specification using the ConfigMap.
• Create the pod.
• 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:

• Katacoda

• Play with Kubernetes

• Understand Using ConfigMap Data in Pods.
• Understand Configure Containers Using a ConfigMap.

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.

1. Create a ConfigMap from the docs/user-guide/configmap/redis/redis-config file:

   kubectl create configmap example-redis-config --from-file=docs/user-guide/configmap/redis/redis-config
   
   kubectl get configmap example-redis-config -o yaml
   

   apiVersion: v1
   data:
     redis-config: |
       maxmemory 2mb
       maxmemory-policy allkeys-lru
   kind: ConfigMap
   metadata:
     creationTimestamp: 2016-03-30T18:14:41Z
     name: example-redis-config
     namespace: default
     resourceVersion: "24686"
     selfLink: /api/v1/namespaces/default/configmaps/example-redis-config
     uid: 460a2b6e-f6a3-11e5-8ae5-42010af00002
   

2. Create a pod specification that uses the config data stored in the ConfigMap:

   apiVersion: v1
   kind: Pod
   metadata:
     name: redis
   spec:
     containers:
     - name: redis
       image: kubernetes/redis:v1
       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
   

3. Create the pod:

   kubectl create -f docs/user-guide/configmap/redis/redis-pod.yaml
   

   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.

4. 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"
   

What’s next

• Learn more about ConfigMaps.
• See Using ConfigMap Data in Pods.