config-map kubernetes multiple environments

Question

I am trying to deploy a Spring Boot application using configuration data from Kubernetes cluster. I have a simple RestController that prints a message by reading from a Kubernetes cluster.

    private String message = "Message not coming from Kubernetes config map";

@RequestMapping(value="/echo", method=GET)
public String printKubeConfig() {
    return message;
}

Specified the name of the config map in my application.yml

spring:
  application:
    name: echo-configmap

echo-configmap

apiVersion: v1
kind: ConfigMap
metadata:
  name: echo-configmap
data:
  application.properties: |-
    message=Hello from dev Kubernetes Configmap
  application_qa.properties: |-
    message=Hello from qa Kubernetes Configmap

I have several environments like qa, int, test etc

What's the best way to specify environment specific properties in the config map? And how to access them in Spring boot application?
Ex: if the application is deployed in qa, my service should return the message "Hello from qa Kubernetes Configmap"
We also have plans to read these configuration files from GIT in future. How to handle that usecase?

Dave Kerr Dave Kerr · Accepted Answer · 2017-12-10T04:43:44

Let me try and provide an answer which I think gives you what you need, without using any tools beyond what you'll have installed on most boxes. Maybe try this first, and if you find the approach becomes difficult to manage and scale, move onto something more sophisticated.

Step 1: Version control configmaps per environment

Create a folder like k8s/configmaps or something, and create one configmap per environment:

k8s/configmaps/properties.dev.yaml
k8s/configmaps/properties.qa.yaml
k8s/configmaps/properties.sit.yaml
k8s/configmaps/properties.uat.yaml

Each configmap should contain your environment specific settings.

Step 2: Have a namespace per environment

Create a k8s namespace per environment, such as:

 application-dev
 application-qa
 application-sit
 application-uat

Step 3: Create the configmap per environment

A little bash will help here:

#!/usr/bin/env bash
# apply-configmaps.sh
namespace="application-${ENVIRONMENT}"
for configmap in ./k8s/configmaps/*.${ENVIRONMENT}.yml; do
    echo "Processing ConfigMap $configmap"
    kubectl apply -n ${namespace} -f $configmap
done

Now all you need to do to create or update configmaps for any environment is:

ENVIRONMENT=dev ./update-configmaps.sh

Step 4: Finish the job with CI/CD

Now you can create a CI/CD pipeline - if your configmap source changes just run the command shown above.

Summary

Based on primitive commands and no special tools you can:

Version control config
Manage config per environment
Update or create config when the config code changes
Easily apply the same approach in a CI/CD pipeline if needed

I would strongly recommend you follow this basic 'first principles' approach before jumping into more sophisticated tools to solve the same problems, in many cases you can do it yourself without much effort, learn the key concepts and save the more sophisticated tooling till later if you really need it.

Hope that helps!