What is pod affinity and node affinity

Question

Hey i'm a newbie to Kubernetes. Could somebody help me in understanding Pod affinity and Node affinity? Thanks in advance.

Answer 1

• Node Affinity ensures that pods are hosted on particular nodes.

• Pod Affinity ensures two pods to be co-located in a single node.

Node Affinity

apiVersion: v1
kind: Pod
metadata:
name: with-node-affinity
spec:
affinity:
nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: Kubernetes.io/e2e-az-name
            operator: In
            values:
            - e2e-az1

Pod Affinity

apiVersion: v1
kind: Pod
metadata:
name: with-pod-affinity
spec:
  affinity:
    podAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
      - labelSelector:
          matchExpressions:
          - key: security
            operator: In
            values:
            - S1

The pod affinity rule says that the pod can be scheduled to a node only if that node is in the same zone as at least one already-running pod that has a label with key “security” and value “S1”

For a better understanding refer to: https://kubernetes.io/docs/concepts/configuration/assign-pod-node/