Reduce Downtime with Rolling Updates and maxSurge in Kubernetes Deployments.
One of the biggest challenges in managing modern applications is keeping services available during updates. Kubernetes solves this challenge elegantly with Rolling Updates and a powerful configuration option called maxSurge.
In this blog, we will explore how these features work together to ensure zero downtime deployments, improve application reliability, and offer a better user experience.
What is a Rolling Update?
A Rolling Update is a deployment strategy in Kubernetes where pods are updated gradually, instead of all at once.
This ensures that some pods with the old version are always available to serve traffic, while the new version is being rolled out.
How does it work?
When you apply a new version of your application, Kubernetes doesn’t destroy all existing pods.
Instead, it creates new pods one by one and removes the old ones only after the new ones are ready.
This keeps the service running, helps avoid disruptions, and offers a smooth user experience.
But what if your traffic load is already at maximum?
How do you make sure new pods come online before old ones are terminated?
That’s where maxSurge plays a key role.
What is maxSurge?
maxSurge is a setting in the Kubernetes Deployment strategy that allows extra pods to be created temporarily during updates.
By default, Kubernetes replaces old pods with new ones while sticking to the original number of replicas.
But when you enable maxSurge, you allow Kubernetes to exceed the desired number of pods just during the update.
Understanding maxSurge: 1
Let’s say your application is running with 3 replicas (pods).
If you set maxSurge: 1, Kubernetes will allow 1 extra pod to be created during the update.
So during the rollout:
You’ll have 4 pods running for a short time.
Once a new pod is ready, Kubernetes will remove one of the old pods.
This continues until all old pods are replaced.
This strategy ensures that there is no gap in service availability and no interruption in user experience.
How maxSurge Helps
Ensures zero downtime during app updates.
Allows Kubernetes to create extra pods temporarily to keep your app running smoothly.
Makes deployments safer by handling live traffic alongside new rollouts.
Prevents performance issues caused by under-provisioning during updates.
Reduces the risk of failed updates by rolling out changes gradually.
Best Practices
To get the most out of maxSurge and Rolling Updates, follow these best practices:
Start with small values like maxSurge: 1 to test the behavior.
Monitor resource limits , creating extra pods may use more CPU/memory temporarily.
Combine with readiness probes to ensure new pods are fully ready before traffic is routed.
Use horizontal pod autoscalers (HPA) to manage workloads more dynamically.
Always test the rollout on staging before applying to production.
YAML Snippet Example
maxSurge: 1 means one extra pod is allowed during update.
maxUnavailable: 0 means no pod should be down at any time during update.
Conclusion
Kubernetes Rolling Updates combined with maxSurge offer a reliable and flexible approach to updating your applications without causing downtime. By temporarily allowing a few extra pods during the deployment process, you can maintain continuous service availability, ensure safer rollouts, and deliver a smoother experience to your users. This approach not only minimizes risks during updates but also keeps your application responsive and resilient. If uptime and seamless deployments are important to your business, leveraging maxSurge should be an essential part of your Kubernetes deployment strategy.