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Kubernetes: 10. Node Selector

Scheduler

  • By default Pods gets scheduled based on node availability for the scheduler
  • There may be cases where in one of the node has more resources and the pod required to be scheduled on this node
  • There are two ways to achieve this
    1. Node Selector
    2. Node Affinity
Node Selector
  • Update the pod definition file with the node selector label
  • Pod will be scheduled on the node matching the label
  • But first, Node has to be labelled. 
  • Within the pod definition spec.nodeSelector is the property to map a pod to a node
  • With node selector, you can only have a simple key-value selection
  • There are no options for advanced selectors like label in certain values, or label not-in a value
pod-definition.yaml
apiVersion: v1
kind: Pod
metadata:
    name: myapp-pod
    labels:
        app: myapp

spec:
    containers:
    - name: nginx-container
      image: nginx

    nodeSelector:
        size: Large
  
kubectl label node <node-name> <label-key>=<label-value> 
-> Set a node label with key value pair

kubectl label node node01 size=Large 
-> Set node01 label size to Large value
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