Background:
Currently we're using Docker and Docker Compose for our services. We have externalized the configuration for different environments into files that define environment variables read by the application. For example a prod.env file:
ENV_VAR_ONE=Something Prod
ENV_VAR_TWO=Something else Prod
and a test.env file:
ENV_VAR_ONE=Something Test
ENV_VAR_TWO=Something else Test
Thus we can simply use the prod.env or test.env file when starting the container:
docker run --env-file prod.env <image>
Our application then picks up its configuration based on the environment variables defined in prod.env.
Questions:
apiVersion: v1
kind: Pod
metadata:
labels:
context: docker-k8s-lab
name: mysql-pod
name: mysql-pod
spec:
containers:
-
env:
-
name: MYSQL_USER
value: mysql
-
name: MYSQL_PASSWORD
value: mysql
-
name: MYSQL_DATABASE
value: sample
-
name: MYSQL_ROOT_PASSWORD
value: supersecret
image: "mysql:latest"
name: mysql
ports:
-
containerPort: 3306
You can populate a container's environment variables through the use of Secrets or ConfigMaps. Use Secrets when the data you are working with is sensitive (e.g. passwords), and ConfigMaps when it is not.
In your Pod definition specify that the container should pull values from a Secret:
apiVersion: v1
kind: Pod
metadata:
labels:
context: docker-k8s-lab
name: mysql-pod
name: mysql-pod
spec:
containers:
- image: "mysql:latest"
name: mysql
ports:
- containerPort: 3306
envFrom:
- secretRef:
name: mysql-secret
Note that this syntax is only available in Kubernetes 1.6 or later. On an earlier version of Kubernetes you will have to specify each value manually, e.g.:
env:
- name: MYSQL_USER
valueFrom:
secretKeyRef:
name: mysql-secret
key: MYSQL_USER
(Note that env take an array as value)
And repeating for every value.
Whichever approach you use, you can now define two different Secrets, one for production and one for dev.
dev-secret.yaml:
apiVersion: v1
kind: Secret
metadata:
name: mysql-secret
type: Opaque
data:
MYSQL_USER: bXlzcWwK
MYSQL_PASSWORD: bXlzcWwK
MYSQL_DATABASE: c2FtcGxlCg==
MYSQL_ROOT_PASSWORD: c3VwZXJzZWNyZXQK
prod-secret.yaml:
apiVersion: v1
kind: Secret
metadata:
name: mysql-secret
type: Opaque
data:
MYSQL_USER: am9obgo=
MYSQL_PASSWORD: c2VjdXJlCg==
MYSQL_DATABASE: cHJvZC1kYgo=
MYSQL_ROOT_PASSWORD: cm9vdHkK
And deploy the correct secret to the correct Kubernetes cluster:
kubectl config use-context dev
kubectl create -f dev-secret.yaml
kubectl config use-context prod
kubectl create -f prod-secret.yaml
Now whenever a Pod starts it will populate its environment variables from the values specified in the Secret.
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