How to guarantee even spread pod distribution across AZ in Kubernetes StatefulSet

user_15013994 0
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I deployed a K8s StatefulSet with 30 replicas (or N replicas, where N is multiple of 3) in EKS Cluster.

EKS cluster is with 3 nodes, one node for one AZ, and I want to guarantee with Kubernetes Affinity/AntiAffinity the equal distribution of pods across different AZ.

us-west-2a (n nodes) -> N/3 pods
us-west-2b (m nodes) -> N/3 pods
us-west-2c (o nodes) -> N/3 pods

Thanks

statefulset amazon-eks kubernetes
2 Answers

While this is too possible with node affinity, a straight forward way is the use of topologySpreadContraints, here's the k8s documentation, diagrams and examples to see it in action.

user_147047990

You can always use selectors and default labels which you get from AWS. A simple pod spec example is here

topologySpreadConstraints:
  - maxSkew: 1
    topologyKey: "topology.kubernetes.io/zone"
    whenUnsatisfiable: DoNotSchedule
    labelSelector:
      matchLabels:
        app: myapp

You can include skew and other options based on the need as described here: https://kubernetes.io/docs/concepts/workloads/pods/pod-topology-spread-constraints/

user_20391520
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