https://drive.google.com/file/d/1i6DcsQp3H-3PkiLRQQR5dnn5O_dCDg_b/view?usp=sharing

🔍 YAML Breakdown

apiVersion: v1
kind: Pod
metadata:
  name: nnappone
  namespace: learning
  labels:
    app: nnappone
spec:
  containers:
    - name: crackone-app
      image: nginx
      resources:
        requests:
          memory: "150Mi"   # ← Minimum guaranteed
        limits:
          memory: "250Mi"   # ← Maximum allowed
# ❌ No CPU resources defined!

🔍 Key Observation:

• Only memory has requests and limits
• CPU has no resources defined → This is enough to make the Pod Burstable (not BestEffort, not Guaranteed)

📌 What Makes a Pod "Burstable"?

A Pod is Burstable if at least one of these is true:

• It has requests ≠ limits for any resource (e.g., memory: 150Mi ≠ 250Mi), OR
• It has requests or limits defined for only some resources (e.g., memory defined, but CPU missing)

✅ Your Pod qualifies because:

• Memory: requests (150Mi) < limits (250Mi) → burst allowed
• CPU: not defined → treated as BestEffort for CPU, but Burstable overall

🎯 Kubernetes Rule:

Burstable = Not BestEffort AND Not Guaranteed

🆚 QoS Comparison (Memory Focus)

💡 Burstable Behavior:

• Gets 150Mi guaranteed at startup (scheduler reserves this).
• Can burst up to 250Mi if node has free memory.
• If memory pressure occurs:
  • Evicted after BestEffort Pods
  • Evicted before Guaranteed Pods
  • Among Burstable Pods: those using more than requested are killed first.

🧪 Lab: Deploy Burstable Pod & Verify QoS

🔧 Steps

# 1. Create namespace
kubectl create namespace learning

# 2. Apply the Pod
kubectl apply -f pod-simple-qos-burstable.yml

# 3. Check Pod status
kubectl get pods -n learning

# 4. Describe Pod → check QoS Class and resources
kubectl describe pod nnappone -n learning | grep -A 5 -B 2 "QoS\\\\|Limits\\\\|Requests"

# ✅ Expected output:
# Requests:
#   memory: 150Mi
# Limits:
#   memory: 250Mi
# QoS Class: Burstable

# 5. (Optional) Extract QoS via JSONPath
kubectl get pod nnappone -n learning -o jsonpath='{.status.qosClass}{"\\\\n"}'

# 6. Clean up
kubectl delete pod nnappone -n learning
kubectl delete namespace learning