Rolling Update Explained

Explanation

In a rolling update, new instances are brought up with the updated version while old instances are gradually terminated. At any point during the deployment, both old and new versions may be running simultaneously. The process continues until all instances run the new version. This contrasts with blue-green deployment (all-at-once switch) and canary deployment (small percentage first). Rolling updates are the default strategy in Kubernetes and most container orchestrators. Key parameters include max surge (how many extra instances during update), max unavailable (how many instances can be down), and health check configuration (verifying new instances are healthy before proceeding).

Bookuvai Implementation

Bookuvai uses rolling updates as the default deployment strategy for Kubernetes-hosted services. We configure health checks to verify new instances before routing traffic, set max unavailable to zero for zero-downtime deployments, and implement readiness probes that delay traffic until the application is fully initialized.

Key Facts

• Gradually replaces old instances with new ones during deployment
• Maintains availability — no downtime during the update process
• Both old and new versions run simultaneously during the transition
• Default deployment strategy in Kubernetes and most orchestrators
• Key parameters: max surge, max unavailable, health check intervals

Related Terms

• Blue-Green Deployment
• Canary Deployment
• Kubernetes

Frequently Asked Questions

What happens if the new version is broken during a rolling update?

Health checks detect unhealthy new instances and halt the rollout. Kubernetes automatically stops the update and can roll back to the previous version. Configure proper liveness and readiness probes to catch issues before they affect users.

How is a rolling update different from blue-green deployment?

Rolling updates gradually replace instances, running both versions simultaneously during transition. Blue-green deployment maintains two complete environments and switches traffic all at once. Blue-green offers instant rollback; rolling updates use fewer resources.

Can rolling updates cause compatibility issues?

Yes. During the transition, both old and new versions handle requests simultaneously. If the new version changes API contracts or database schemas, requests may fail. Ensure backward compatibility or use blue-green deployment for breaking changes.