Kubernetes: Configuring Topology Spread Constraints to tune Pod scheduling

2 min read

Ensuring high availability and fault tolerance in a Kubernetes cluster is a complex task: One important feature that allows us to addresses this challenge is Topology Spread Constraints.

10/07/2023

Kubernetes: How to configure Deployment to evenly spread Pods across availability zones

5 min read

If you run Kubernetes workloads on AWS you want to make sure Pods are spread across all the available availability zones. To do so we can use podAntiAffinity to tell Kubernetes to avoid deploying all the Pods of the same deployment on the same AZ

28/03/2022

How to avoid pods of the same Deployment to be scheduled on the same node

2 min read

For some applications we might want to avoid having two or more Pods belonging to the same Deployment to be scheduled on different nodes, yet we don't need them to be a DaemonSet. Let's use as an example the cluster autoscaler: We would like to have two replicas but not on the same node, since if we are draining the node an there's not enough capacity on the other nodes with both Pods offline a manual intervention would be required to spawn a new node

$ kubectl get pods -n autoscaler -o wide
NAME                                                 READY   STATUS    RESTARTS   AGE     IP              NODE                                           NOMINATED NODE   READINESS GATES
autoscaler-aws-cluster-autoscaler-585cc546dd-jc46d   1/1     Running   0          16h     10.103.195.47   ip-10-12-16-10.eu-west-1.compute.internal    <none>           <none>
autoscaler-aws-cluster-autoscaler-585cc546dd-s4j2r   1/1     Running   0          16h     10.103.195.147  ip-10-12-16-10.eu-west-1.compute.internal    <none>           <none>

To do so we will have to configure affinity

11/08/2021