AWS offers a great service called “Amazon Elastic Container Service for Kubernetes” (AWS EKS).
The setup guide can be found here: Offical AWS EKS getting started guide
If you overload such a cluster it easily happens that your Kubelet gets “Out of Memory” (OOM) errors and stops working.
Once the Kubelet is down you can see
kubectl get nodes that node is in state “NotReady”.
In addition if you describe your node
kubectl describe $NODE you can see the status description is: “System OOM encountered”.
If you look on your pods
kubectl get pods --all-namespaces you can see that pods are in state “Unknown” or in “NodeLost”.
Kubelet OOM errors should be avoided by all costs.
It causes to stop all pods on that node and its quite complicated for K8s to maintain high availability for applications in some cases.
For example for stateful sets with a single replica k8s cannot immediately move that pod to another node.
The reason is that k8s does not know how long the node with all its pods stays unavailable.
Therefore i like to share some best practice to avoid OOM problems in your AWS EKS clusters.
In the first article of this series, Getting started with AWS Lambda, we used a Cloudformation template to provision and deploy all needed parts for our REST application.
In this and the following articles, we are going to explore components used in the template. The focus of this article is the network infrastructure components.
Kubernetes and OpenShift have a lot in common. Actually OpenShift is more or less Kubernetes with some additions. But what exactly is the difference?
It’s not so easy to tell as both products are moving targets. The delta changes with every release - be it of Kubernetes or OpenShift. I tried to find out and stumbled across a few blog posts here and there. But they all where based on not so recent versions - thus not really up-to-date.
So I took the effort to compare the most recent versions of Kubernetes and OpenShift. At the time of writing v1.13 of Kubernetes and v3.11 of OpenShift. I plan to update this article as new versions become available.