node-affinity.yaml

# 1.  Add the label role=web to one of the nodes
#
#   kubectl label nodes <node-name> role=web
#
# 2. Deploy this manifest and check which nodes the pods are deployed.
# 
#   kubectl create -f node-affinity.yaml
# 
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-node-affinity
  labels:
    run: nginx-node-affinity
spec:
  replicas: 2
  selector:
    matchLabels:
      run: nginx-node-affinity
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  template:
    metadata:
      labels:
        run: nginx-node-affinity
    spec:
      affinity:
        nodeAffinity:
          requiredDuringSchedulingIgnoredDuringExecution:
          #You can have multiple nodeSelectorTerms.  The pod will be scheduled to a
          #node if one of the nodeSelectorTerms are satisfied.
            nodeSelectorTerms:
            #you can have multiple matchExpressions
            #The pod will be scheduled to a node only if ALL matchExpressions can be satisfied.
            - matchExpressions:
              - key: role
                operator: In #valid values are: In, NotIn, Exists, DoesNotExist, Gt, Lt
                values:
                - web    
          #The node that is most preferred is the one with the greatest sum of weights
          preferredDuringSchedulingIgnoredDuringExecution:
          - weight: 1
            preference:
              matchExpressions:
              - key: role
                operator: In
                values:
                - web      
      containers:
      - name: nginx-node-affinity
        image: nginx