What is an HPA?
- Docker & Kubernetes course
- Advanced
- Lesson 37/70
- 4 min
Learn autoscaling with a HorizontalPodAutoscaler.
What is an HPA?
A HorizontalPodAutoscaler (HPA) automatically changes a Deployment's (or StatefulSet's) replica count with load. At intervals (15 s by default) it looks at the pods' metrics and calculates the replica count needed to hit the target:
desired = ceil( current_replicas × current_value / target_value )
# 4 replicas, average CPU 90%, target 60%
ceil(4 × 90 / 60) = 6 replicas"Horizontal" scaling changes the pod count; "vertical" scaling (VPA) changes the resources per pod.
An HPA by command
A quick HPA is created with kubectl autoscale. kubectl get hpa shows the current and target values side by side:
$ kubectl autoscale deployment api --cpu-percent=70 --min=2 --max=10
horizontalpodautoscaler.autoscaling/api autoscaled
$ kubectl get hpa
NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE
api Deployment/api cpu: 35%/70% 2 10 2 1mPractice Autoscale
Write two commands: create an HPA for the api deployment with a 70% CPU target, at least 2 and at most 10 replicas; list the HPAs.
Starter code
# buraya yazSample solution
kubectl autoscale deployment api --cpu-percent=70 --min=2 --max=10
kubectl get hpaExpected output
horizontalpodautoscaler.autoscaling/api autoscaled NAME REFERENCE TARGETS MINPODS MAXPODS REPLICAS AGE api Deployment/api cpu: 35%/70% 2 10 2 30s
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 With 3 replicas, average CPU 20% and a 50% target, how many replicas does the HPA want (assuming minReplicas 1)?
- 6
- 2 Correct answer
- 3
- 1
Explanation: ceil(3 × 20 / 50) = ceil(1.2) = 2.
2 Create autoscaling for the deployment.
kubectl ____ deployment api --cpu-percent=70 --min=2 --max=10kubectl autoscale deployment api --cpu-percent=70 --min=2 --max=10Explanation: autoscale creates an HPA object.
3 Match.
| Term | Meaning |
|---|---|
HPA |
Changes the pod count |
VPA |
Changes pod resources |
TARGETS 35%/70% |
Current/target |
15 sn |
Evaluation interval |