Kubernetes Rolling Update Strategy Guide

💡 Quick Answer: Configure rolling update strategies for zero-downtime deployments in Kubernetes. Covers maxSurge, maxUnavailable, rollback, and deployment health checks.

The Problem

This is one of the most searched Kubernetes topics. Having a comprehensive, well-structured guide helps both beginners and experienced users quickly find what they need.

The Solution

Rolling Update Configuration

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
spec:
  replicas: 10
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 25%          # Max extra pods during update (2-3 extra)
      maxUnavailable: 25%    # Max pods unavailable during update
  template:
    spec:
      containers:
        - name: app
          image: web-app:v2
          readinessProbe:     # Critical for safe rollouts!
            httpGet:
              path: /ready
              port: 8080
            initialDelaySeconds: 5
            periodSeconds: 5
          livenessProbe:
            httpGet:
              path: /healthz
              port: 8080
            initialDelaySeconds: 15
  minReadySeconds: 10         # Wait 10s after ready before continuing
  revisionHistoryLimit: 10    # Keep 10 ReplicaSets for rollback

Perform a Rolling Update

# Update image
kubectl set image deployment/web-app app=web-app:v2

# Watch rollout
kubectl rollout status deployment/web-app

# Rollout history
kubectl rollout history deployment/web-app

# Rollback
kubectl rollout undo deployment/web-app
kubectl rollout undo deployment/web-app --to-revision=3

# Pause/resume (canary-like)
kubectl rollout pause deployment/web-app
# Check new pods manually
kubectl rollout resume deployment/web-app

Strategy Comparison

graph LR
    A[v1: 10 pods] --> B[Start: create 2 v2 pods]
    B --> C[v2 pods ready → terminate 2 v1]
    C --> D[Create 2 more v2 pods]
    D --> E[Continue until all v2]
    E --> F[v2: 10 pods - done]

Frequently Asked Questions

What happens if a rolling update fails?

If new pods fail readiness probes, the rollout stalls (doesn’t proceed). Existing v1 pods keep serving traffic. Run kubectl rollout undo to roll back.

How do I do blue-green deployments?

Switch the Service selector between v1 and v2 Deployments. Or use Argo Rollouts for automated blue-green with analysis.

Best Practices

• Start simple — use the basic form first, add complexity as needed
• Be consistent — follow naming conventions across your cluster
• Document your choices — add annotations explaining why, not just what
• Monitor and iterate — review configurations regularly

Key Takeaways

• This is fundamental Kubernetes knowledge every engineer needs
• Start with the simplest approach that solves your problem
• Use kubectl explain and kubectl describe when unsure
• Practice in a test cluster before applying to production