Affinity.md

Affinity

We are using 2 types of affinities right now. It solves architectural problems such as node selection and pod deployment on nodes.

Need better understanding on this.

podAntiAffinity

It makes sure that only one pod of deployment statys on a nod. That is only one pod per app can stay on a node.

Add following lines in deployment:template:spec

      affinity:
        podAntiAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          - labelSelector:
              matchExpressions:
              - key: app
                operator: In
                values:
                - test-aws-k8s-master
            topologyKey: "kubernetes.io/hostname"

nodeAffinity

It makes sure that the deployment goes to the specific instance group.

      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/instancegroup
                operator: In
                values:
                - nodes

Here kubernetes.io/instancegroup is key and nodes is value.