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Node Selector

Node selector make a scheduling decision to place a pod on a subset of nodes.

  • nodeSelector - assign Pods to Nodes using Labels and Selectors
  • Apply Labels to Nodes
  • Scheduler will assign Pods a to a Node with a matching Label
  • Simple key/value check based on matchLabels
  • Often used to map Pods to Nodes based on...
    • Special hardware requirements
    • Workload isolation

Scheduling​

Scheduling

They are two Nodes, one with labels S and G, and one with just label S.

  • If I create a pod with label S, the pod is scheduled normally.
  • If I create a pod with label G, the pod is scheduled only is the first node
  • If I create a pod with no label, the pod is scheduled normally
  • If I create a pod with a label R, the pod is not scheduled and pending, because the label is a requirement spec in the pod

Assigning Pods to Nodes using Node Selectors​

They are two steps

Assign a label to a node

kubectl label node c1-node2 hardware=local_gpu

Inside the pod specs

spec:
    containers:
    - name: hello-world
      image: gcr.io/google-samples/hello-app:1.0
      ports:
      - containerPort: 8080
    nodeSelector:
      hardware: local_gpu

Demo

Checks labels for more information