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kubernetes-hands-on/15-hpa-vpa/README.md

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HPA, VPA

HPA

HPA means Horizontal Pod Autoscaler. It automatically scales the number of pods in a replication controller, deployment or replica set based on observed CPU utilization (or, with custom metrics support, on some other application-provided metrics).

Let's take an example with CPU usage:

apiVersion: autoscaling/v1
kind: HorizontalPodAutoscaler
metadata:
  name: simple-hpa
spec:
  maxReplicas: 10
  minReplicas: 3
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: my-deployment
targetCPUUtilizationPercentage: 80
  • spec: the spec for the HPA
    • maxReplicas: the maximum number of pods running
    • minReplicas: the minimum number of pods running
    • scaleTargetRef: what this HPA targets, here a Deployment named simple-deployment
  • targetCPUUtilizationPercentage: the percentage of CPU utilization to cross to activate the HPA

Let's see an HPA in action. This exemple is inspired by the official Kubernetes documentation.

To see it in action, we need to have a workload that consumes some CPU. We'll use an image that is CPU intensive: https://hub.docker.com/r/googlecontainer/hpa-example.

This image computes the square root of numbers:

<?php
  $x = 0.0001;
  for ($i = 0; $i <= 1000000; $i++) {
    $x += sqrt($x);
  }
  echo "OK!";
?>

First, you need to active the metric-server on minikube:

minikube addons enable metrics-server

Review and apply the file 01-hpa.yml.

Now let's generate some load on our service:

kubectl run -i --tty load-generator --image=busybox /bin/sh

Then run in this terminal:

while true; do wget -q -O- http://hpa-example; done

In another terminal look at the state of the pods and the hpa, remember the -w flag on kubectl.

Wait a bit and see how it changes the pods and the hpa.

Stop the load generator, again, wait a bit and see how it changes the pods and the hpa.

VPA

VPA means Vertical Pod Autoscaler. It automatically find the right resources for pods in a replication controller, deployment or replica set based on observed CPU utilization.

This feature is in beta, understand you can install it in your cluster but it's not integrate with the standard k8s source code.

If you are adventurous you can try it by:

  1. Install metrics-server.
  2. Install the vpa.
  3. Try the exemple from the vpa github repo

Exercices

Nothing to see here.

Clean up

kubectl delete service,deployment,pod,crd,vpa --all

Links