Kubernetes pod level configuration externalization in spring boot app - kubernetes

Question

I need some help from the community, I'm still new to K8 and Spring Boot. Thanks all in advance.
what I need is to have 4 K8 pods running in K8 environment and each pod have slightly different configuration from each other, for example, I have a property in one of my java class called regions, it extract it's value from Application.yml, like
#Value("${regions}")
Private String regions;
Now after deploy it to K8 env I want to have 4 pods(I can configure it in helm file) running and in each pod the regions field should have different value.
Is this something achievable ? Can anyone please give any advice ?

Answer 1

If you want to run 4 different pods with different configurations, you have to deploy the 4 different deployments in kubernetes.
You can create the different configmap as per need storing the whole Application.yaml file or environment variables and inject it to different deployments.
how to store whole application.yaml inside config map
apiVersion: v1
kind: ConfigMap
metadata:
name: yaml-region-first
data:
application.yaml: |-
data: test,
region: first-region
the same way you can create the config map with the second deployment.
apiVersion: v1
kind: ConfigMap
metadata:
name: yaml-region-second
data:
application.yaml: |-
data: test,
region: second-region
you can inject this configmap to each deployment
example :
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: hello-app
name: hello-app
namespace: default
spec:
progressDeadlineSeconds: 600
replicas: 1
revisionHistoryLimit: 10
selector:
matchLabels:
app: hello-app
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
creationTimestamp: null
labels:
app: hello-app
spec:
containers:
- name: nginx
image: nginx
imagePullPolicy: IfNotPresent
volumeMounts:
- mountPath: /etc/nginx/app.yaml
name: yaml-file
readOnly: true
volumes:
- configMap:
name: yaml-region-second
optional: false
name: yaml-file
accordingly, you can also create the helm chart.
If you just to pass the single environment instead of storing the whole file inside the configmap you can directly add value to the deployment.
Example :
apiVersion: v1
kind: Pod
metadata:
name: print-greeting
spec:
containers:
- name: env-print-demo
image: bash
env:
- name: REGION
value: "one"
- name: HONORIFIC
value: "The Most Honorable"
- name: NAME
value: "Kubernetes"
command: ["echo"]
args: ["$(GREETING) $(HONORIFIC) $(NAME)"]
https://kubernetes.io/docs/tasks/inject-data-application/define-environment-variable-container/
for each deployment, your environment will be different and in helm, you can dynamically also update or overwrite it using CLI command.