crunchie84 / kubernetes-example-custom-hpa

Example custom horizontal pod autoscaler for Kubernetes

Demo/Example custom horizontal pod autoscaler

This repository contains a demo app + custom hpa to show how to utilize the Kubernetes API for retrieval and modification of the state of kubernetes as a whole.

demo app

The demo app is a simple webserver which does request/sec counting and exposes this metric at the /rate endpoint.

development

• npm install
• npm start

The following urls are available:

• curl localhost:8080/ to have requests counting
• curl localhost:8080/rate to retrieve the current rate of requests to the pod

custom hpa

The custom HPA retrieves the list of pods from the kubernetes master and for each pod fetches the /rate endpoint to retrieve its current rate of requests.

development

• npm install
• npm start

Fast iterating kubernetes deploy + development

You can use the following concatinated expression to build the container, delete current pods and have it be used. Because we are re-using the same version after deleting the pod in the cluster it uses the new image.

• APP: docker build -t example-custom-hpa/app:1.0.0 -f app/Dockerfile ./app && kubectl get pods | grep my-app | awk '{print $1}' | xargs kubectl delete pod
• HPA: docker build -t example-custom-hpa/hpa:1.0.0 -f hpa/Dockerfile ./hpa && kubectl get pods | grep hpa | awk '{print $1}' | xargs kubectl delete pod

Get the demo running (using minikube)

minikube setup

• get minikube up and running locally using this guide
• link your docker commandline to the docker daemon inside minikube by invoking eval $(minikube docker-env). That way the images you build using docker are immediately available on the minikube node as if they are cached from the repository and no further setup is required.

demo app

• Build the app container docker build -t example-custom-hpa/app:1.0.0 -f app/Dockerfile ./app
• Deploy the app to kubernetes kubectl create -f app/deployment.yaml
• Deploy the service to kubernetes kubectl create -f app/service.yaml so you can route traffic to the pods
• Observe that it works by invoking minikube service my-app which connects you to the service
• Observe that it works by looking at the logs kubectl get pods | grep my-app | awk '{print $1}' | xargs kubectl logs -f

custom hpa

• Build the hpa container docker build -t example-custom-hpa/hpa:1.0.0 -f hpa/Dockerfile ./hpa
• Deploy the hpa to kubernetes kubectl create -f app/deployment.yaml
• Observe that it works by looking at the logs kubectl get pods | grep my-custom-hpa | awk '{print $1}' | xargs kubectl logs -f

scale traffic using ab

Lets hit it with some traffic. The IP address + port of the demo app is retrieved using minikube service my-app

• ab -n 1000 -c 3 http://192.168.99.100:31284/ update the ip address as returned from the above command
• Observe the logs of the HPA using kubectl get pods | grep my-custom-hpa | awk 'END {print $1}' | xargs kubectl logs -f