task-034-configuring-environment-variables-in-application

Configuring the environment variables in applications

• plain test

env:
  - name: APP_NAME
    value: test-app

• configmap

env:
  - name: APP_NAME
    valueFrom:
      configMapKeyRef: ...

• secrets

env:
  - name: APP_NAME
    valueFrom:
      secretKeyRef: ...

Creating configmaps Imperative Approach

• Here is the command format

kubectl create configmap \
  <config-name>  --from-literal=<key>=<value>

• Consider the following example

kubectl create configmap \
  app-config --from-literal=APP_NAME=test-app

• If you want to take input from the file

kubectl create configmap \
  app-config --from-file=<path_to_file>

kubectl create configmap \
  app-config --from-file=app_config.properties

Creating configmaps Declarative Approach

my-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-configmap
data:
    APP_NAME: test_app
    APP_ENV: dev

• Apply the configmap

kubectl apply -f my-configmap.yaml

• To view the configmap

kubectl get configmaps

How to inject the config map in pods

• Env

    envFrom:
      - configMapRef:
          name: app-config

• Single Env

env:
  name: APP_COLOR
  valueFrom:
    configMapKeyRef:
      name: app-config
      key: APP_COLOR

• Volume

volumes:
- name: app-config-volume
  secret:
    secretName: app-config

For example

• Injecting the above app-configmap in the pod

apiVersion: v1
kind: Pod
metadata:
  name: pod-name
spec:
  containers:
  - name: container-name
    image: ubuntu
    envFrom:
      - configMapRef:
          name: app-configmap

What is the environment variable name set on the container in the pod?

$ kubectl describe pod webapp-color  | grep -A 2 -i env
    Environment:
      APP_COLOR:  pink
    Mounts:

Describe the configmap db-config

controlplane $ kubectl describe configmap db-config
Name:         db-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
DB_HOST:
----
SQL01.example.com
DB_NAME:
----
SQL01
DB_PORT:
----
3306
Events:  <none>

Create a new ConfigMap for the 'webapp-color' POD. Use the spec given on the right.

• ConfigName Name: webapp-config-map
• Data: APP_COLOR=darkblue

$ kubectl create configmap webapp-config-map --from-literal=APP_COLOR=darkblue
configmap/webapp-config-map created

Update the environment variable on the POD use the newly created ConfigMap

• Pod Name: webapp-color
• EnvFrom: webapp-config-map

controlplane $ kubectl get pod webapp-color -o yaml > pod.yaml

controlplane $ kubectl apply -f pod.yaml
pod/webapp-color created

controlplane $ cat pod.yaml | grep -A 3 -i envfrom
    envFrom:
      - configMapRef:
          name: webapp-config-map
    name: webapp-color