Zero Downtime during AWS EKS Version upgrade

In this article we will see about how AWS ensures zero downtime during version upgrade. We have used terraform for AWS EKS (Elastic Kubernetes Service) version upgrade. We have been using automated version upgrade for versions 1.30, 1.31 and 1.32 successfully. One common observation during these upgrades is rolling update process. It ensures zero downtime during this version upgrade activity.

What is rolling update?

Rolling update ensure new version pods are created and starts running. After its successful running in ready status, the old version pods are scaled down. This is ensured for cluster worker nodes as well. New worker nodes are scaled up in new version and pods are provisioned. After the successful running of the new version pods, the old version pods are scaled down followed by scale down of old version nodes.

Can we do version upgrade without announcing downtime to stakeholders?

No, it is best practise to announce downtime during an eks version upgrade. Teams can stop planning critical activities during this period. Also, teams will be prepared with back up for any disastrous or unexpected system behaviors.