Kubernetes Static Vs Dynamic Config Maps

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Kubernetes Static Vs Dynamic Config Maps

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Today's use case is all about Static vs. Dynamic Configurations in Kubernetes with a real-world example to show you how to keep your deployments up-to-date with the latest changes.

To begin with, what is a ConfigMap?

It's an API object in Kubernetes used to store non-confidential configuration data as key-value pairs, enabling the decoupling of configuration artifacts from image content for better application portability.

When distinguishing between static and dynamic ConfigMaps in Kubernetes, it's all about management and updates.

Static ConfigMaps are created and updated manually, requiring users to reapply changes and possibly restart pods to apply the new configurations.

Dynamic ConfigMaps are more hands-off, updating automatically from external sources or through processes that refresh the running pods without the need for restarts. This allows for smoother and more efficient configuration management in dynamic environments.

As we see in the below example:

Static configurations are simple and easy to implement but come with significant limitations.

• No Real-time Updates: Any change in the configuration map requires a manual redeployment of the pods to pick up the changes.

• Downtime: Manually updating configurations can lead to downtime or inconsistent states during the deployment process.

• Scalability: Managing configurations manually does not scale well, especially in large and dynamic environments.

A static configuration looks like this, watch out of ‘configMapKeyRef’ :

apiVersion: apps/v1
kind: Deployment
metadata:
  name: node-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: node-app
  template:
    metadata:
      labels:
        app: node-app
    spec:
      containers:
      - name: node-app
        image: node-app:latest
        ports:
        - containerPort: 3000
        env:
        - name: DATABASE_URL
          valueFrom:
            configMapKeyRef:
              name: static-db-config
              key: DATABASE_URL

To overcome these limitations, dynamic configurations allow your deployments to pick up changes in real-time without requiring a manual redeployment.

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Let's get back to the context,

A dynamic configuration looks like this with a CONFIG_RELOAD_INTERVAL :

apiVersion: apps/v1
kind: Deployment
metadata:
  name: node-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: node-app
  template:
    metadata:
      labels:
        app: node-app
    spec:
      containers:
      - name: node-app
        image: node-app:latest
        ports:
        - containerPort: 3000
        env:
        - name: DATABASE_URL
          valueFrom:
            configMapKeyRef:
              name: dynamic-db-config
              key: DATABASE_URL
        - name: CONFIG_RELOAD_INTERVAL
          value: 30 # Reload config every 30 seconds

Points to Consider Before Implementing Dynamic Configs:

1. Application Compatibility: Ensure your application can handle configuration changes at runtime without requiring a restart.

2. Security: Dynamic updates might introduce security risks if sensitive configurations are exposed or not properly validated.

3. Performance Overhead: Continuously checking for updates might introduce some performance overhead; evaluate the impact on your application.

4. Testing: Thoroughly test dynamic configurations in a staging environment to catch potential issues before rolling them out to production.

5. Logging and Monitoring: Implement robust logging and monitoring to track configuration changes and quickly identify any issues caused by updates.

Remember, Kubernetes and peace of mind usually don't go hand in hand, but with dynamic configurations, at least we try not to lose a day of sleep on upgrade days :)

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