Bits of .NET

⭐ DNS Pods Should Evict Batch Jobs

When cluster is full, which pods get evicted? Priority Classes define importance. Critical pods survive. Batch jobs go first.

📝 Define Priority Classes

apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: critical
value: 1000000000
globalDefault: false
description: "Critical system pods that must never be evicted"

---
apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: high
value: 1000000
globalDefault: false
description: "High priority user workloads"

---
apiVersion: scheduling.k8s.io/v1
kind: PriorityClass
metadata:
  name: low
value: 1000
globalDefault: true  # Default for all pods without priority
description: "Low priority batch jobs"

# System priorities (already exist):
# system-cluster-critical (2B)
# system-node-critical (2B)

🎯 Using Priority Classes

apiVersion: v1
kind: Pod
metadata:
  name: critical-dns
spec:
  priorityClassName: critical  # Never evicted
  containers:
  - name: dns
    image: coredns

---
apiVersion: batch/v1
kind: Job
metadata:
  name: data-processing
spec:
  template:
    spec:
      priorityClassName: low  # Will be evicted first
      containers:
      - name: processor
        image: processor:latest
      restartPolicy: Never

💡 Eviction Order (Lowest to Highest)

• Batch jobs (priority: 1000) → evicted first
• User workloads (priority: 1000000)
• Critical system (priority: 1000000000)
• DaemonSet pods (never evicted)
• Static pods (never evicted)