🚀 1-Click Demo — Replicable Guide

Turn any Spring Boot web app into a "1-Click Demo" SaaS trial system.

Users sign up → click "Start Trial" → get a live, isolated instance with its own subdomain and SSL certificate. Fully automated.

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⚠️ Placeholders

Throughout this guide, the following placeholders are used. Replace them with your actual values:

Placeholder	Description	Example
{{APP_NAME}}	Your app name (lowercase, no spaces)	factoryplatform
{{APP_DISPLAY_NAME}}	Your app's display name	Factory Platform
{{MANAGER_PORT}}	Manager spring boot app port	8885
{{APP_PORT}}	The port for containers	8080
{{DOMAIN}}	Your base domain	numankaraaslan.com
{{DOCKERHUB_USER}}	Your Docker Hub username	numankaraaslan
{{DOCKER_REPO}}	Docker Hub repository name for trial image	factory-trial
{{VPS_IP}}	Your VPS public IP address	178.105.213.245
{{MANAGER_VPS_IP}}	Your Manager app VPS IP (may be the same)	4.231.171.39
{{YOUR_EMAIL}}	Your email for Let's Encrypt	numan4634@gmail.com
{{DB_NAME_MANAGER}}	Database name for manager app	factoryplatform-manager
{{DB_PASSWORD_MANAGER}}	Database password for manager app	123456789
{{DB_NAME}}	Database name inside the container	factoryplatform
{{DB_PASSWORD}}	Database password inside the container	trial
{{SPRING_PROFILE}}	Spring profile for trial mode	trial

Note

For multi-module Spring Boot projects (like a reactor POM with shared modules), the Dockerfile.trial must be placed at the repo root so that the Docker build context can access all modules. The build command then uses -pl your-service -am to build only the target module and its dependencies.

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Architecture

┌─────────────────────────────┐         ┌───────────────────────────────────┐
│  Manager VPS                │         │  Trial VPS (K3s)                  │
│  ┌───────────────────────┐  │         │  ┌─────────────────────────────┐  │
│  │ Manager App            │  │ K8s API │  │ Traefik (ports 80/443)      │  │
│  │ (Spring Boot + DB)     │──────────>│  │ cert-manager (Let's Encrypt) │  │
│  │                        │  │ :6443   │  │                             │  │
│  │ Sign up → Start Trial  │  │         │  │ Trial Pods:                 │  │
│  │   → Creates K8s Pod    │  │         │  │   demo42.example.com        │  │
│  │   → Creates Service    │  │         │  │   demo99.example.com        │  │
│  │   → Creates Ingress    │  │         │  │   ...                       │  │
│  └───────────────────────┘  │         │  └─────────────────────────────┘  │
└─────────────────────────────┘         └───────────────────────────────────┘

How it works:

1. User signs up on the Manager web app
2. Clicks "Start Free Trial"
3. Manager app uses Kubernetes Java Client to create: Deployment + Service + Ingress
4. K3s Traefik routes traffic, cert-manager issues SSL
5. User gets a live instance at demo42.{{DOMAIN}} within ~60 seconds
6. Trial expires after {{TTL_HOURS}} — Manager deletes the K8s resources

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Guide Structure

#	File	What it covers
1	01-trial-dockerfile.md	Bundling your Spring Boot app + PostgreSQL into a self-contained Docker image
2	02-vps-setup.md	VPS + K3s + cert-manager + wildcard DNS + firewall
3	03-manager-app.md	The Manager app — K8s provisioning with Java Client
4	04-docker-publish-script.md	VPS-based Docker build/push script
5	05-rbac-and-templates.md	ServiceAccount, RBAC, K8s YAML templates
6	06-aks-scaling.md	Scaling to Azure AKS (managed Kubernetes)

🥔 Potatobrained Guides (real-world cheat sheets)

File	What it covers
potatobrained-vps.md	Step-by-step VPS/K3s setup with real commands and credentials
potatobrained-aks.md	Step-by-step AKS setup with real commands and credentials

⚠️ The potatobrained files contain real tokens and certificates. Do not push to a public repo.

Template files

File	Description
templates/Dockerfile.trial	Generic trial Dockerfile
templates/supervisord.conf	supervisord config
templates/init-db.sh	Database init script
templates/docker-publish.sh	VPS Docker build/push script
templates/trial-k8s-setup.yaml	Namespace + quota + RBAC + secrets

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Cost

Resource	Monthly Cost
VPS (Hetzner CX22, 4GB RAM)	~€4
K3s	€0 (open source)
cert-manager + Let's Encrypt	€0
Docker Hub (1 private repo)	€0 (free tier)
Total	~€4/month

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Scaling Path

Start cheap, scale when needed:

€4/month VPS (K3s)  →  AKS / EKS / GKE (managed Kubernetes)

Migration = change 3 config values in the Manager app:

• k8s.api-server
• k8s.token
• k8s.ca-cert

Same code, bigger infrastructure.