🎓 LEVEL 46 DEBRIEF: Taints & Tolerations¶

Congratulations! You've mastered taints and tolerations - the gatekeepers of node scheduling!

📊 What You Fixed¶

Problem: Node tainted, pod has no toleration

# Node: dedicated=gpu:NoSchedule
# Pod: No tolerations → Can't schedule

Solution: Added matching toleration

tolerations:
- key: "dedicated"
  operator: "Equal"
  value: "gpu"
  effect: "NoSchedule"

Result: Pod schedules successfully

🎯 Understanding Taints & Tolerations¶

Taints (Node-level)¶

Purpose: Repel pods from nodes

kubectl taint nodes node1 key=value:Effect

Effects: - NoSchedule: New pods can't schedule - PreferNoSchedule: Avoid scheduling (soft) - NoExecute: Evict existing + block new

Tolerations (Pod-level)¶

Purpose: Allow scheduling on tainted nodes

tolerations:
- key: "gpu"
  operator: "Equal"
  value: "true"
  effect: "NoSchedule"

🔧 Common Patterns¶

Dedicated Nodes¶

# Taint GPU nodes
kubectl taint nodes gpu-node dedicated=gpu:NoSchedule

# Only GPU workloads tolerate
tolerations:
- key: "dedicated"
  value: "gpu"
  effect: "NoSchedule"

Maintenance Mode¶

# Drain node (NoExecute)
kubectl taint nodes node1 maintenance=true:NoExecute

# Evicts all pods without toleration

Spot Instances¶

# Mark as spot
kubectl taint nodes spot-1 node.kubernetes.io/instance-type=spot:PreferNoSchedule

# Dev workloads tolerate
tolerations:
- key: "node.kubernetes.io/instance-type"
  operator: "Exists"

💥 Common Mistakes¶

Missing effect: Must match taint effect
Typo in key/value: Case-sensitive!
Wrong operator: "Equal" needs value, "Exists" doesn't
Forgetting NoExecute: Evicts running pods

🎯 Key Takeaways¶

Taints repel, tolerations allow
All parts must match: key, value, effect
NoExecute evicts existing pods
operator: Exists tolerates any value
Use for: dedicated nodes, maintenance, special hardware

🚀 Next Steps¶

Level 47: PodDisruptionBudget
Level 48: Admission Webhooks
Level 49: PriorityClass
Level 50: CHAOS FINALE!

Excellent work! 🎉⚡