DockerCoins - Kubernetes Learning Lab

A simple cryptocurrency mining simulator for learning Kubernetes concepts.

What is DockerCoins?

DockerCoins is an educational application that simulates cryptocurrency mining. It consists of 5 microservices that work together:

• rng - Generates random bytes (Python/Flask)
• hasher - Computes SHA256 hashes (Ruby/Sinatra)
• worker - Coordinates the mining process (Python)
• webui - Shows mining statistics (Node.js/Express)
• redis - Stores data (standard Redis image)

Architecture

                     ┌──────────┐
                     │  webui   │ ◄── You view this in browser
                     └────┬─────┘
                          │ reads
                          ▼
┌────────┐  bytes   ┌──────────┐  hash   ┌──────────┐
│  rng   │ ◄─────── │  worker  │ ──────► │  hasher  │
└────────┘          └────┬─────┘         └──────────┘
                         │ writes
                         ▼
                    ┌──────────┐
                    │   redis  │
                    └──────────┘

See full walkthrough in [LAB.md]

Before You Start

Personalize Your WebUI

Edit webui/files/index.html and replace YOUR_NAME with your actual name:

<h1>DockerCoin Miner - YOUR_NAME</h1>

Change to:

<h1>DockerCoin Miner - John Smith</h1>

Building and Pushing Images

Set your Docker Hub username:

export DOCKER_USER=your_dockerhub_username

Build and push all images:

# Build all images
docker build -t $DOCKER_USER/rng:v1 ./rng
docker build -t $DOCKER_USER/hasher:v1 ./hasher
docker build -t $DOCKER_USER/worker:v1 ./worker
docker build -t $DOCKER_USER/webui:v1 ./webui

# Push to Docker Hub
docker push $DOCKER_USER/rng:v1
docker push $DOCKER_USER/hasher:v1
docker push $DOCKER_USER/worker:v1
docker push $DOCKER_USER/webui:v1

Create Deployments

kubectl create deployment redis --image=redis
kubectl create deployment rng --image=$DOCKER_USER/rng:v1
kubectl create deployment hasher --image=$DOCKER_USER/hasher:v1
kubectl create deployment worker --image=$DOCKER_USER/worker:v1
kubectl create deployment webui --image=$DOCKER_USER/webui:v1

Verify pods are running:

kubectl get pods

Wait until all pods show Running status.

Create Services

kubectl expose deployment redis --port 6379
kubectl expose deployment rng --port 80
kubectl expose deployment hasher --port 80
kubectl expose deployment webui --type=NodePort --port=80

Open Web UI

minikube service webui

Your app will be automatically opened in a web browser:

Cleanup

When you want to start fresh or clean up after the lab:

Step 1: Delete the Minikube cluster

minikube delete

This stops and removes the entire Kubernetes cluster.

Step 2: Remove local Docker images

First, set your Docker Hub username (replace with your actual username):

export DOCKER_USER=your_dockerhub_username

Then remove the images:

docker rmi $DOCKER_USER/rng:v1
docker rmi $DOCKER_USER/hasher:v1
docker rmi $DOCKER_USER/worker:v1
docker rmi $DOCKER_USER/webui:v1

If you get "image is being used" errors, force removal with -f flag:

docker rmi -f $DOCKER_USER/rng:v1
docker rmi -f $DOCKER_USER/hasher:v1
docker rmi -f $DOCKER_USER/worker:v1
docker rmi -f $DOCKER_USER/webui:v1

Step 3: Delete repositories from Docker Hub

1. Go to Docker Hub
2. Log in to your account
3. Click Repositories
4. For each repository (rng, hasher, worker, webui):
   • Click the repository name
   • Click Settings tab
   • Scroll down → Delete repository
   • Type the repository name to confirm

License

This is a modernized version of the original DockerCoins demo by Jérôme Petazzoni. Used for educational purposes.