Completek8s Classroomnotes 20/Sep/2023

Scheduling and Tooling

  • K8s Cluster can contain multiple nodes and workloads are scheduled on the node by kube-schedule and there are different factors influencing the decision to select the node
    • node selector
    • node affinity
    • taints and tolerations
  • Container Resource Limits influence this decision as kube-Scheduler will sum all the requests of container in a Pod spec and schedules it on a suitable node
  • If the Pod doesnot schedule due to insufficient resources available on nodes in the Events we will see the following reasons
    • PodExceedsFreeCpu
    • PodExceedsFreeMemory


  • Refer Here for official docs
  • Lets label two nodes
    • node2:
      • labels
        • diskspeed=high
    • node3:
      • labels:
        • diskspeed=low
  • Lets create a Pod and specify the selection based on diskspeed=high which has a match and one more pod which doesnot match. Refer Here for the changeset
  • Pod will be scheduled on node matching labels but not on not matching scenarios

Node Affinity

  • Refer Here for official docs
  • Refer Here for nodeAffinity with hard and soft rules
  • Non Matching hard will not be scheduled
  • podAffinity speaks about running a pod on the same node as some other pod with matching conditions and reverse of it is podAntiAffinity
  • Refer Here for the manifests

Taints and Tolerations

  • Taint is a property of a node to repel the pods. Only pods who have toleration for the taint will be scheduled on the node.
  • Usecases:
    • Dedicated Hardware:
    • Evictions
  • Refer Here for official docs
  • Taint Effects:
    • NoSchedule
    • NoExecute
    • PreferNoShedule
  • Taint nodes kubectl taint nodes <node-name> <taint:key>=<taint:value>:<taint-effect>

Yaml Processor

  • The tool yq is used to read, modify and enhance contents of YAML file.
  • Refer Here for the docs
  • Exercise 1: Try more samples on modifying yaml files
  • Exercise 2:
  • Create a Deployment using nopCommerce Docker image
  • Create a stateful set using mysql Container

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