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Node Affinity

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In this section, we will talk about “Node Affinity” feature in kubernetes.

The primary feature of Node Affinity is to ensure that the pods are hosted on particular nodes.

• With Node Selectors we cannot provide the advance expressions. ``` apiVersion: v1 kind: Pod metadata: name: myapp-pod spec: containers:
  • name: data-processor image: data-processor nodeSelector: size: Large

    ![ns-old](/k8s.github.io/images/ns-old.PNG)
    

    apiVersion: v1 kind: Pod metadata: name: myapp-pod spec: containers:

  • name: data-processor image: data-processor affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: size operator: In values: - Large - Medium ```

  apiVersion: v1
  kind: Pod
  metadata:
   name: myapp-pod
  spec:
   containers:
   - name: data-processor
     image: data-processor
   affinity:
     nodeAffinity:
       requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: size
              operator: NotIn
              values: 
              - Small
  

  

  apiVersion: v1
  kind: Pod
  metadata:
   name: myapp-pod
  spec:
   containers:
   - name: data-processor
     image: data-processor
   affinity:
     nodeAffinity:
       requiredDuringSchedulingIgnoredDuringExecution:
          nodeSelectorTerms:
          - matchExpressions:
            - key: size
              operator: Exists
  

  

Node Affinity Types

• Available
  • requiredDuringSchedulingIgnoredDuringExecution
  • preferredDuringSchedulingIgnoredDuringExecution
• Planned
  • requiredDuringSchedulingRequiredDuringExecution
  • preferredDuringSchedulingRequiredDuringExecution

  

Node Affinity Types States

K8s Reference Docs

• https://kubernetes.io/docs/tasks/configure-pod-container/assign-pods-nodes-using-node-affinity/
• https://kubernetes.io/blog/2017/03/advanced-scheduling-in-kubernetes/