Progressive delivery concept in Kubernetes - Commands & Configuration

Introduction

Progressive delivery helps release new software versions slowly and safely. It reduces risks by exposing changes to a small group first, then gradually to everyone.

When you want to test a new app version with a small group of users before full release

When you want to reduce downtime or errors during software updates

When you want to monitor new features and roll back quickly if problems appear

When you want to deploy updates multiple times a day without affecting all users

When you want to gather feedback from real users on new changes before full rollout

Config File - deployment.yaml

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  labels:
    app: my-app
spec:
  replicas: 5
  selector:
    matchLabels:
      app: my-app
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app-container
        image: my-app:1.1
        ports:
        - containerPort: 80

This file defines a Kubernetes Deployment for the app.

replicas: number of app copies running.

strategy: RollingUpdate means new version replaces old gradually.

maxSurge: how many extra pods can run during update (1 here).

maxUnavailable: how many pods can be down during update (1 here).

This setup allows progressive delivery by updating pods one by one safely.

Commands

This command creates or updates the Deployment with the new app version and rolling update strategy.

Terminal

kubectl apply -f deployment.yaml

Expected Output

deployment.apps/my-app created

This command checks the progress of the rolling update to ensure pods update successfully one by one.

Terminal

kubectl rollout status deployment/my-app

Expected Output

deployment "my-app" successfully rolled out

This command lists all pods of the app to see how many are running the new version during the rollout.

Terminal

kubectl get pods -l app=my-app

Expected Output

NAME                       READY   STATUS    RESTARTS   AGE

my-app-5d8f7c7d7f-abc12   1/1     Running   0          2m

my-app-5d8f7c7d7f-def34   1/1     Running   0          1m

my-app-5d8f7c7d7f-ghi56   1/1     Running   0          30s

my-app-5d8f7c7d7f-jkl78   1/1     Running   0          10s

my-app-5d8f7c7d7f-mno90   1/1     Running   0          5s

If the new version causes problems, this command rolls back to the previous stable version quickly.

Terminal

kubectl rollout undo deployment/my-app

Expected Output

deployment.apps/my-app rolled back

Key Concept

If you remember nothing else from this pattern, remember: update your app gradually to catch problems early and keep users safe.

Common Mistakes

Setting maxUnavailable to 0 during rolling update

This prevents any pod from being unavailable, which can delay updates and cause longer rollout times.

Set maxUnavailable to at least 1 to allow one pod to update at a time for smooth progressive delivery.

Not checking rollout status after applying update

You might miss errors or failed updates causing downtime or broken app versions.

Always run 'kubectl rollout status' to monitor update progress and catch issues early.

Deploying new version to all pods at once

This causes full downtime or exposes all users to bugs at once.

Use rolling update strategy with maxSurge and maxUnavailable to update pods gradually.

Summary

Create a Deployment with rolling update strategy to update pods gradually.

Use 'kubectl apply' to deploy changes and 'kubectl rollout status' to monitor progress.

Roll back quickly with 'kubectl rollout undo' if problems occur during update.