#053 Kubernetes - Environment Variables

Introduction

this is part 53 from the journey it's a long journey(360 day) so go please check previous parts , and if you need to walk in the journey with me please make sure to follow because I may post more than once in 1 Day but surely I will post daily at least one 😍.

And I will cover lot of tools as we move on.

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Environment Variables

if we remember the example of voting app we have something in the yml file > spec called env , it's our environment variables it's same as docker where you can pass variables between container in case of docker and Pods in case of Kubernetes.

# db-deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: db
  name: db
spec:
  replicas: 1
  selector:
    matchLabels:
      app: db
  template:
    metadata:
      labels:
        app: db
    spec:
      containers:
      - image: postgres:9.4
        name: postgres
        env:
        - name: POSTGRES_USER
          value: postgres
        - name: POSTGRES_PASSWORD
          value: postgres
        ports:
        - containerPort: 5432
          name: postgres
        volumeMounts:
        - mountPath: /var/lib/postgresql/data
          name: db-data
      volumes:
      - name: db-data
        emptyDir: {} 

this is the old file from voting app , if we just focus on this part

 env:
        - name: POSTGRES_USER
          value: postgres
        - name: POSTGRES_PASSWORD
          value: postgres

we can see that we are passing the username and the password as variables so we didn't hard coded inside our code.
but wait we have now 2 variables one in docker and one in Kubernetes with same env names ?
Kubernetes will override your environment variables in the docker file.
example let's say that we specify an environment variable inside of docker

ENV DBURL mongodb://localhost:27017/OrdersDB

and inside our Kubernetes config we override it

env:
  - name: DBURL
    value: mongodb://mongo:80/OdersDB

mongo is the name of our service in this case and 80 is the port of the service.

we can control our environment variables , in big projects we have lot of environment variables so it's very hard to manage them in this way , also maybe some of them are secretes like tokens.