Feature flags in Kubernetes - Commands & Configuration

Introduction

Feature flags let you turn parts of your app on or off without changing code. In Kubernetes, you can use ConfigMaps to manage these flags easily and update your app behavior without redeploying.

When you want to enable a new feature for testing without redeploying your app

When you need to quickly disable a feature causing issues in production

When you want to gradually roll out a feature to some users by changing config

When you want to keep one app version but change behavior based on flags

When you want to separate feature control from app code for easier updates

Config File - feature-flags-configmap.yaml

feature-flags-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: feature-flags
  namespace: default
data:
  newFeatureEnabled: "true"
  betaFeature: "false"

This ConfigMap stores feature flags as key-value pairs.

newFeatureEnabled controls if the new feature is active.

betaFeature controls a beta feature toggle.

Your app reads these values to decide which features to run.

Commands

Create or update the ConfigMap with feature flags in Kubernetes.

Terminal

kubectl apply -f feature-flags-configmap.yaml

Expected Output

configmap/feature-flags created

Check the current feature flags stored in the ConfigMap.

Terminal

kubectl get configmap feature-flags -o yaml

Expected Output

apiVersion: v1

data:

  betaFeature: "false"

  newFeatureEnabled: "true"

kind: ConfigMap

metadata:

  name: feature-flags

  namespace: default

  resourceVersion: "12345"

  uid: abcdef12-3456-7890-abcd-ef1234567890

→

-o yaml - Outputs the ConfigMap in YAML format for easy reading

Restart the app deployment to pick up updated feature flags if your app reads them on startup.

Terminal

kubectl rollout restart deployment my-app

Expected Output

deployment.apps/my-app restarted

View detailed information about the feature flags ConfigMap.

Terminal

kubectl describe configmap feature-flags

Expected Output

Name:         feature-flags

Namespace:    default

Labels:       <none>

Annotations:  <none>

Data

====

betaFeature:

false

newFeatureEnabled:

true

Events:       <none>

Key Concept

If you remember nothing else from this pattern, remember: use ConfigMaps to store feature flags so you can change app behavior without changing code or rebuilding images.

Common Mistakes

Changing the ConfigMap but not restarting the app pods

The app may not reload the new flags until restarted, so changes have no effect.

Restart the deployment or pods after updating the ConfigMap if your app reads flags only on startup.

Storing feature flags inside the app code instead of ConfigMaps

You lose flexibility to toggle features without redeploying the app.

Use ConfigMaps to separate feature flags from code for easy updates.

Using non-string values in ConfigMap data

ConfigMap data must be strings; other types cause errors or unexpected behavior.

Always store feature flag values as strings like "true" or "false".

Summary

Create a ConfigMap to hold feature flags as key-value pairs.

Apply the ConfigMap with kubectl apply -f to create or update it.

Check the ConfigMap contents with kubectl get or describe commands.

Restart your app deployment to apply new flags if your app reads them on startup.