09-Node-Affinity.md

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
  

  

  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/