Affinity

The affinity value defines rules for node affinity and pod affinity/anti-affinity.

info

The default value for affinity is:

affinity: {}

By default the affinity field is empty.

You can add affinity rules to this field that give you a few more options for pod scheduling than nodeSelector.

Node Affinity

You can use Node affinity to achieve something very similar to the nodeSelector.

affinity:
  nodeAffinity:
    requiredDuringSchedulingIgnoredDuringExecution:
      nodeSelectorTerms:
        - matchExpressions:
            - key: topology.kubernetes.io/zone
              operator: In
              values:
                - antarctica-east1
                - antarctica-west1

With the configuration above the GoKubeDownscaler will only be scheduled on a Node where the label topology.kubernetes.io/zone exists and has either the value antarctica-east1 or antarctica-west1.

Pod Affinity

Pod affinity on the other hand will compare the labels of all pods on a Node.

affinity:
  podAntiAffinity:
    preferredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
            - key: env
              operator: In
              values:
                - test

With this configuration the GoKubeDownscaler will only try to deploy the pods on a Node where no other pod has the label env=test.

For more information on affinity you can reference the official Kubernetes documentation.