Kubernetes pod affinity - Scheduling pods on different nodes

Question

We are running our application with 3 pods on a 3 node kubernetes cluster. When we deploy out application, sometimes, pods are getting scheduled to the same kubernetes node.

We want our pods to scheduled in such a way that it spread our pods across nodes ( no 2 pods of the same application should be same node). Infact, as per documentation( https://kubernetes.io/docs/concepts/configuration/assign-pod-node/ ), kubernetes already does a good job in this. However, if it doesn't find resources, it schedules it to the same node. How do it make it a hard constraint ?

Requirement: We want the deployment to fail or be in pending state if the pods don't obey the constraints (no 2 pods of the same application should be same node)

Answer 1

i think this one will work

affinity:
    podAntiAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: app
            operator: In
            values:
            - <VALUE>
        topologyKey: "kubernetes.io/hostname"

For more reference you can visit : https://thenewstack.io/implement-node-and-pod-affinity-anti-affinity-in-kubernetes-a-practical-example/