Horizontal Pod Autoscaler

Overview

What HPA does

Automatically scales the number of Pods in a replication controller, deployment, replica set or stateful set based on observed CPU utilization or with custom metrics.

API Object

API Group: autoscaling
CPU autoscaling: autoscaling/v1
memory & custom metrics: autoscaling/v2beta2

Kubectl

kubectl autoscale rs foo --min=2 --max=5 --cpu-percent=80

Examples

CPU

Install metrics-server

The HorizontalPodAutoscaler normally fetches metrics from a series of aggregated APIs (metrics.k8s.io, custom.metrics.k8s.io, and external.metrics.k8s.io). The metrics.k8s.io API is usually provided by metrics-server
```
kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
```

Apply an apache application

kubectl apply -f https://k8s.io/examples/application/php-apache.yaml

Set autoscale by kubectl

kubectl autoscale deployment php-apache --cpu-percent=50 --min=1 --max=10

kubectl get hpa
NAME         REFERENCE               TARGETS         MINPODS   MAXPODS   REPLICAS   AGE
php-apache   Deployment/php-apache   <unknown>/50%   1         10        0          9s

apiVersion: autoscaling/v1
kind: HorizontalPodAutoscaler
metadata:
  name: php-apache
  namespace: default
spec:
  maxReplicas: 10
  minReplicas: 1
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: php-apache
  targetCPUUtilizationPercentage: 50

Increase the load

kubectl run -i --tty load-generator --rm --image=busybox --restart=Never -- /bin/sh -c "while sleep 0.01; do wget -q -O- http://php-apache; done"

kubectl get hpa

NAME         REFERENCE               TARGETS   MINPODS   MAXPODS   REPLICAS   AGE
php-apache   Deployment/php-apache   76%/50%   1         10        7          4m10s