Kubernetes ConfigMap

Create ConfigMap for Redis Cache

kubectl create configmap example-redis-config --from-file=$HOME/core-k8s/labs/configmap/config/redis-config

Verify ConfigMap looks correct

kubectl get configmap example-redis-config -o yaml

It should look something like

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

Create Redis POD that uses ConfigMap

kubectl create -f $HOME/core-k8s/labs/configmap/manifests/redis-pod.yaml

Confirm Redis POD launched with ConfigMap settings

kubectl exec -it redis -- redis-cli

Execute the following commands:

CONFIG GET maxmemory

Output:

1) "maxmemory"
2) "2097152"

CONFIG GET maxmemory-policy

Output:

1) "maxmemory-policy"
2) "allkeys-lru"

Exit the redis container

exit

Cleanup

kubectl delete pod redis

ConfigMap Nginx

Now that you’ve had some experience creating a ConfigMap, let’s build on that and setup an Nginx reverse proxy that sends traffic to a NodeJS web application.

Doing things on your own

Create ConfigMap

Look in the config directory and you will see reverseproxy.conf which contains the configuration for our Nginx reverse proxy.

1. Create a ConfigMap with this file called nginx-config
2. Create nginx.yaml to create a Pod with the following attributes:
   • Container 1
     • name: helloworld-nginx
     • label: app: helloworld-nginx
     • image: nginx
     • port: 80
     • Mount configMap nginx-config to /etc/nginx/conf.d with
       • key of reverseproxy.conf
       • path of reverseproxy.conf
   • Container 2
     • name: k8s-demo
     • image: aslaen/k8s-demo
     • port 3000
3. Create nginx-service.yaml to expose the application
   • name: helloworld-nginx-service
   • port: 80
   • protocol: TCP
   • Selector: app: helloworld-nginx
   • type: NodePort

Validate

Now run curl to connect to server on port 80 and confirm you get:

* Rebuilt URL to: 0:80/
*   Trying 0.0.0.0...
* TCP_NODELAY set
* Connected to 0 (127.0.0.1) port 80 (#0)
> GET / HTTP/1.1
> Host: 0
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Server: nginx/1.15.9
< Date: Thu, 28 Feb 2019 05:55:55 GMT
< Content-Type: text/html; charset=utf-8
< Content-Length: 12
< Connection: keep-alive
< X-Powered-By: Express
< ETag: W/"c-7Qdih1MuhjZehB6Sv8UNjA"
<
* Connection #0 to host 0 left intact
Hello World!

We can see that it connects to Nginx and then returns Hello World! which is what we’ve defined in our Node.js app in the k8s-demo container.

Now to confirm the traffic is actually being passed through the proxy update the ConfigMap to pass traffic to port 3001 and redeploy. You should see it fail to connect.

Lab Complete!