Autoscaling Practice

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QUESTIONS

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🔥 Question 1 — Memory-based HPA with Custom Behavior

Objective

Configure a Horizontal Pod Autoscaler that scales only on memory utilization and uses custom scaling behavior.

Requirements

• Deployment name: mem-hpa
• Image: polinux/stress
• Command:

  ["sleep", "3600"]

• Resource requests:

  memory: 50Mi

HPA configuration:

• Metric: memory utilization
• Target: 80%
• Min replicas: 1
• Max replicas: 5

Behavior:

• Scale up: +2 pods per 30 seconds
• Scale down: −1 pod per 60 seconds
• Scale-down stabilization window: 300 seconds

Load Generation

POD=$(kubectl get pods -l app=mem-hpa -o name | shuf -n 1) && \
echo "Running stress in: $POD" && \
kubectl exec "$POD" -- sh -c \
'nohup stress --vm 1 --vm-bytes 200Mi --timeout 600 > /dev/null 2>&1 &'

Observation

watch -n 5 '
kubectl top po;
echo "-----";
kubectl get po -l app=mem-hpa
'

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🔥 Question 2 — CPU + Memory HPA with Complex Custom Behavior

Objective

Configure a multi-metric HPA that scales on CPU OR memory, using asymmetric, production-style behavior rules.

Requirements

• Deployment name: multi-hpa
• Image: polinux/stress
• Command:

  ["sleep", "3600"]

• Resource requests:

  cpu: 40m
  memory: 60Mi

HPA configuration:

• CPU target: 65%
• Memory target: 75%
• Min replicas: 2
• Max replicas: 8

Behavior:

• Scale up:

  • Max of 4 pods OR 50% per 30 seconds
  • Select policy: Max

• Scale down:

  • −1 pod per 90 seconds
  • Stabilization window: 300 seconds

Load Generation

POD=$(kubectl get pods -l app=multi-hpa -o name | shuf -n 1) && \
echo "Running stress in: $POD" && \
kubectl exec "$POD" -- sh -c \
'nohup stress --cpu 2 --vm 1 --vm-bytes 180Mi --timeout 600 > /dev/null 2>&1 &'

Observation

watch -n 10 '
kubectl describe hpa multi-hpa | grep -A15 "Metrics:";
echo "-----";
kubectl get po -l app=multi-hpa
'

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🚀 Question 3 — VPA in Off Mode

Objective

Validate that VPA Off mode only observes usage and never mutates pods.

Requirements

• Deployment name: vpa-off

• Image: polinux/stress

• Command:

  ["sleep", "3600"]

• Initial requests:

  cpu: 20m
  memory: 30Mi

• VPA configuration:

  • Update mode: Off
  • Min allowed: 30m / 40Mi
  • Max allowed: 200m / 200Mi

Load Generation

kubectl exec deploy/vpa-off -- sh -c \
'stress --cpu 2 --vm 1 --vm-bytes 100Mi --timeout 600'

Observation

kubectl describe vpa vpa-off

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🚀 Question 4 — VPA in Initial Mode

Objective

Understand how VPA Initial mode injects requests only at pod creation time.

Requirements

• Deployment name: vpa-initial

• Image: polinux/stress

• Command:

  ["sleep", "3600"]

• Initial requests:

  cpu: 10m
  memory: 20Mi

• VPA configuration:

  • Update mode: Initial
  • Min allowed: 20m / 30Mi
  • Max allowed: 100m / 100Mi

Load Generation

kubectl exec deploy/vpa-initial -- sh -c \
'stress --cpu 1 --vm 1 --vm-bytes 60Mi --timeout 600'

Observation

watch -n 30 '
kubectl describe vpa vpa-initial | grep -A8 -B6 "Recommendation"
'

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🚀 Question 5 — VPA in Auto Mode (Fully Configured)

Objective

Observe automatic pod eviction and recreation when VPA actively enforces sizing.

Requirements

• Deployment name: vpa-auto

• Image: polinux/stress

• Command:

  ["sleep", "3600"]

• Initial requests:

  cpu: 15m
  memory: 25Mi

• VPA configuration:

  • Update mode: Auto
  • Min allowed: 20m / 30Mi
  • Max allowed: 150m / 200Mi
  • Controlled resources: CPU and memory

Load Generation

POD=$(kubectl get pods -l app=vpa-auto -o name | shuf -n 1) && \
echo "Running stress in: $POD" && \
kubectl exec "$POD" -- sh -c \
'nohup stress --cpu 3 --vm 1 --vm-bytes 150Mi --timeout 300 > /dev/null 2>&1 &'

Observation

watch -n 15 '
kubectl get po -l app=vpa-auto
'

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