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k8s-learning

A repository created to learn kubernetes concepts.

Pre-requisites

  • Install docker, kubernetes
  • Install minikube
  • Enable the following addons on minikube
    • minikube addons enable ingress
    • minikube addons enable registry

Components in the project

The project contains the following components:

  • Frontend - Written in javascript and requires an nginx server
  • Backend - Written in go

The frontend and backend are packaged into docker images that are then used in the kubernetes deployment

K8s Cluster architecture

The K8s cluster has the following configuration

  • Single node cluster
  • 3 replicas of frontend
  • 3 replicas of backend
  • 1 LoadBalancer service each for frontend and backend
  • 1 nginx Ingress controller configured with dns configured for test-app.local domain

Detailed description of each component

Frontend

  • Deployment configured to have 3 replicas with labels app: test-react-app and tier: frontend
  • Container image: localhost:5000/testapp:latest
  • Image created using the frontend Dockerfile
  • nginx server + react app

Backend

  • Deployment configured to have 3 replicas with labels app: test-backend-app and tier: backend
  • Container image: localhost:5000/testbackend:latest
  • Image created using the backend Dockerfile
  • Go + Gin

How to generate images

  • Enable the registry addon for minikube by running minikube addons enable registry

  • Run docker build for either the frontend or backend by running:

    cd testapp
docker build -t testapp .
docker tag testapp localhost:5000/testapp
    cd backend
docker build -t testbackend .
docker tag testbackend localhost:5000/testbackend

  • Redirect port 5000 to point to the container registry in the minikube cluster by running the following script in a different terminal

    scripts/registry-port-forward.sh

    Then, run the following scripts to push the docker images to the container registry

    docker push localhost:5000/testapp
docker push localhost:5000/testbackend

Setup hosts

The host test-app.local needs to be added to the system's hosts file.

Get the IP address of the minikube host:

> minikube ip
192.168.58.2

Use this IP to bind it to the test-app.local domain

vi /etc/hosts

Add the following line to the hosts file (use the minikube host IP address)

192.168.58.2	test-app.local

Run the K8s deployment

At this point, the K8s deployment can be run by running the following:

cd deployment
kubectl apply -f test-deployment.yaml
  • This creates 6 pods for frontend and backend
  • test-app.local/* will always point to one of the frontend pods depending on availability and load
  • test-app.local/backend/* will always point to one of the backend pods depending on availability and load - in these requests, the /backend/ is stripped off and the rest of the path is passed on to the pods

The frontend screenshot at http://test-app.local/ Frontend

The backend screenshot at http://test-app.local/backend/albums Backend