Pod Priority and Preemption

Pod Priority and Preemption An architecture diagram generated by Archify. PriorityClass · Priority class · Priority and Preemption Mechanism PriorityClass Priority class Pod · priorityClassName · Priority and Preemption Mechanism Pod priorityClassName Preemption · scheduler action · Priority and Preemption Mechanism Preemption scheduler action Lower-priority pods · removed · Priority and Preemption Mechanism Lower-priority pods removed 1. Scheduling failure · resource shortage · Preemption process 1. Scheduling failure resource shortage 2. Select target pods · Preemption process 2. Select target pods 3. Terminate target pods · termination signal sent · Preemption process 3. Terminate target pods termination signal sent 4. Schedule the pod · higher-priority pod placed · Preemption process 4. Schedule the pod higher-priority pod placed assigns priority resource shortage removes starts preemption process triggers selects completes Priority and Preemption Mechanism Preemption process Legend Scheduler / Pods Priority policy Removed pods

Priority Class Examples

  • • system-node-critical: 2000000000 (pods critical for node operation)
  • • system-cluster-critical: 1000000000 (pods critical for cluster operation)
  • • high-priority: custom, e.g. 1000000
  • • default: 0 (no PriorityClass specified)

Preemption Considerations

  • • Preempted pods terminate gracefully within terminationGracePeriodSeconds
  • • Preemption does not respect PodDisruptionBudget