Guides

Horizontal Pod Autoscaler: Load के नीचे Scale

By Ravindra Bagale, DevOps trainer · LinkedIn · Published: 28 October 2026 · Last updated: 28 October 2026

metrics-server, CPU requests, HPA min/max+target, load, replicas बढ़ना+cool down.

Language: English · मराठी · हिंदी

HPA क्यों

Spike पर ज़्यादा pods.

Why: Fixed replicas = रात बेकार / sale टूटे. What: HPA replicas बदलता है. How: CPU resource metric.

Example 1: Confirm metrics-server idea

Type this:

printf '%s\n' 'kubectl get apiservice v1beta1.metrics.k8s.io -o jsonpath="{.status.conditions[0].status}" 2>/dev/null || echo NEED_METRICS_SERVER'

You will see:

NEED_METRICS_SERVER

What it means: HPA needs metrics-server (or equivalent) before CPU targets work.

Example 2: Deployment with resources

Type this:

mkdir -p /tmp/hpa && printf '%s\n' 'apiVersion: apps/v1' 'kind: Deployment' 'metadata: {name: web}' 'spec:' '  replicas: 1' '  selector: {matchLabels: {app: web}}' '  template:' '    metadata: {labels: {app: web}}' '    spec:' '      containers:' '      - name: web' '        image: public.ecr.aws/docker/library/nginx:1.27-alpine' '        resources:' '          requests: {cpu: "100m"}' '          limits: {cpu: "200m"}' > /tmp/hpa/deploy.yaml && grep -A2 requests /tmp/hpa/deploy.yaml

You will see:

requests: {cpu: "100m"}

What it means: Requests give HPA a baseline; without them CPU % is meaningless.

Example 3: HPA YAML

Type this:

printf '%s\n' 'apiVersion: autoscaling/v2' 'kind: HorizontalPodAutoscaler' 'metadata: {name: web}' 'spec:' '  scaleTargetRef:' '    apiVersion: apps/v1' '    kind: Deployment' '    name: web' '  minReplicas: 1' '  maxReplicas: 5' '  metrics:' '  - type: Resource' '    resource: {name: cpu, target: {type: Utilization, averageUtilization: 50}}' > /tmp/hpa/hpa.yaml && head -4 /tmp/hpa/hpa.yaml

You will see:

apiVersion: autoscaling/v2

What it means: min/max and CPU target — Flipkart-style web tier pattern.

Concept 1: Apply/watch

Object पहले.

Why: बिना HPA load एक pod जलाता है. What: apply; get -w. How: TARGETS आते हैं.

Example 4: Apply commands

Type this:

printf '%s\n' 'kubectl apply -f deploy.yaml -f hpa.yaml && kubectl get hpa'

You will see:

kubectl apply -f deploy.yaml -f hpa.yaml && kubectl get hpa

What it means: TARGETS column fills once metrics arrive.

Example 5: Watch HPA

Type this:

printf '%s\n' 'kubectl get hpa web -w'

You will see:

kubectl get hpa web -w

What it means: REPLICAS climbs when utilization stays above the target.

Example 6: Generate load sketch

Type this:

printf '%s\n' 'kubectl run load --rm -it --image=public.ecr.aws/docker/library/busybox:1.36 -- /bin/sh -c "while true; do wget -q -O- http://web/; done"'

You will see:

kubectl run load --rm -it --image=public.ecr.aws/docker/library/busybox:1.36 -- /bin/sh -c "while true; do wget -q -O- http://web/; done"

What it means: Steady traffic — Infosys labs use a loop, not one curl.

Concept 2: Load/events

Traffic + describe.

Why: बिना Events अनुमान. What: busybox loop. How: Events पढ़ें.

Example 7: Describe HPA events

Type this:

printf '%s\n' 'kubectl describe hpa web | sed -n "/Events/,+12p"'

You will see:

kubectl describe hpa web | sed -n "/Events/,+12p"

What it means: Events explain why it scaled or stayed put.

Example 8: Scale bounds

Type this:

printf '%s\n' 'minReplicas: 1' 'maxReplicas: 5  # cost ceiling for labs and startups'

You will see:

minReplicas: 1
maxReplicas: 5  # cost ceiling for labs and startups

What it means: Max is a bill guardrail as much as a capacity knob.

Example 9: Cool-down note

Type this:

printf '%s\n' 'After load stops, wait for the stabilization window before replicas drop'

You will see:

After load stops, wait for the stabilization window before replicas drop

What it means: Do not panic if scale-down is slower than scale-up.

Concept 3: Bounds

max = cost cap.

Why: Lab भूलना महँगा. What: max; delete -f. How: HPA vs VPA.

Example 10: Custom metric hint

Type this:

printf '%s\n' 'CPU first; custom metrics (queue depth) come after metrics-server works'

You will see:

CPU first; custom metrics (queue depth) come after metrics-server works

What it means: Beginners should prove Resource metrics before custom adapters.

Example 11: Delete lab

Type this:

printf '%s\n' 'kubectl delete -f hpa.yaml -f deploy.yaml'

You will see:

kubectl delete -f hpa.yaml -f deploy.yaml

What it means: Clean labs keep shared clusters tidy.

Example 12: Interview one-liner

Type this:

printf '%s\n' 'HPA changes replica count; VPA changes pod size — different knobs'

You will see:

HPA changes replica count; VPA changes pod size — different knobs

What it means: Amazon/TCS interviews love this contrast.

HPA card

1 metrics-server 2 requests 3 HPA 4 apply 5 load 6 watch

Suppose: unknown targets

Fix metrics-server.

Suppose: no scale

requests + real load.

Check yourself (quiz)

metrics → HPA → load → scale → cool down. Did you understand? Let us try it once more.