Microservices Lab

A polyglot microservices architecture demo with an API Gateway, built using FastAPI (Python), Django REST Framework (Python), ASP.NET Core (C#), and Express.js (Node.js).

Architecture Overview

                    ┌──────────────────┐
                    │   API Gateway    │
                    │  (Express.js)    │
                    │   Port: 8080     │
                    └────────┬─────────┘
                             │
            ┌────────────────┼────────────────┐
            │                │                │
   ┌────────▼───────┐ ┌─────▼──────┐ ┌───────▼────────┐
   │  Item Service   │ │Order Service│ │Payment Service │
   │   (FastAPI)     │ │  (Django)   │ │ (ASP.NET Core) │
   │   Port: 8081    │ │ Port: 8082  │ │  Port: 8083    │
   └────────────────┘ └────────────┘ └────────────────┘

Tech Stack

Service	Framework	Language	Port
API Gateway	Express.js	JavaScript	8080
Item Service	FastAPI + Uvicorn	Python	8081
Order Service	Django REST Framework	Python	8082
Payment Service	ASP.NET Core 8	C#	8083

---

Project Structure

microservices-lab/
├── api-gateway/          # Node.js API Gateway
│   ├── index.js
│   ├── package.json
│   └── Dockerfile
├── ItemService/          # FastAPI Item Service
│   ├── main.py
│   ├── requirements.txt
│   └── Dockerfile
├── OrderService/         # Django Order Service
│   ├── manage.py
│   ├── requirements.txt
│   ├── Dockerfile
│   ├── OrderService/
│   │   ├── settings.py
│   │   └── urls.py
│   └── orders/
│       ├── views.py
│       └── urls.py
├── PaymentService/       # ASP.NET Core Payment Service
│   ├── Program.cs
│   ├── PaymentService.csproj
│   ├── appsettings.json
│   ├── Dockerfile
│   └── PaymentService/
│       ├── Controllers/
│       │   └── PaymentController.cs
│       ├── Models/
│       │   └── Payment.cs
│       └── Services/
│           └── PaymentStore.cs
└── docker-compose.yml

---

Getting Started

Prerequisites

• Docker & Docker Compose
• (Optional for local dev) Node.js, Python 3.11+, .NET 8 SDK

Run All Services with Docker Compose

# Clone the repository
git clone https://github.com/chamithusithmaka/microservices-lab.git
cd microservices-lab

# Build and start all services
docker-compose up --build

# Stop all services
docker-compose down

All services will start automatically. The API Gateway will be available at http://localhost:8080.

---

Running Services Individually (Local Development)

1. Item Service (FastAPI)

cd ItemService
pip install -r requirements.txt
uvicorn main:app --host 0.0.0.0 --port 8081

2. Order Service (Django)

cd OrderService
pip install -r requirements.txt
python manage.py migrate
python manage.py runserver 0.0.0.0:8082

3. Payment Service (ASP.NET Core)

cd PaymentService
dotnet run

4. API Gateway (Express.js)

Note: When running locally, update the proxy targets in api-gateway/index.js from Docker service names (e.g., http://item-service:8081) to http://localhost:8081, etc.

cd api-gateway
npm install
node index.js

---

API Endpoints

Via API Gateway (http://localhost:8080)

Item Service

Method	URL	Description	Request Body
GET	http://localhost:8080/items	Get all items	—
GET	http://localhost:8080/items/0	Get item by index	—
POST	http://localhost:8080/items	Add a new item	{ "name": "Tablet" }

Order Service

Method	URL	Description	Request Body
GET	http://localhost:8080/orders	Get all orders	—
GET	http://localhost:8080/orders/1	Get order by ID	—
POST	http://localhost:8080/orders/create	Create a new order	{ "item": "Laptop", "quantity": 2 }

Payment Service

Method	URL	Description	Request Body
GET	http://localhost:8080/payments	Get all payments	—
GET	http://localhost:8080/payments/1	Get payment by ID	—
POST	http://localhost:8080/payments/process	Process a payment	{ "orderId": 1, "amount": 1000, "method": "Card" }

---

Direct Service Access (without Gateway)

Item Service (http://localhost:8081)

Method	URL	Description
GET	http://localhost:8081/	Get all items
GET	http://localhost:8081/0	Get item by index
POST	http://localhost:8081/	Add a new item

Order Service (http://localhost:8082)

Method	URL	Description
GET	http://localhost:8082/	Get all orders
GET	http://localhost:8082/1	Get order by ID
POST	http://localhost:8082/create	Create a new order

Payment Service (http://localhost:8083)

Method	URL	Description
GET	http://localhost:8083/	Get all payments
GET	http://localhost:8083/1	Get payment by ID
POST	http://localhost:8083/process	Process a payment

---

Testing with Postman

Step 1: Create an Order

• Method: POST
• URL: http://localhost:8080/orders/create
• Headers: Content-Type: application/json
• Body (raw JSON):

{
  "item": "Laptop",
  "quantity": 2
}

• Expected Response (201):

{
  "item": "Laptop",
  "quantity": 2,
  "id": 1,
  "status": "PENDING"
}

Step 2: Process a Payment

• Method: POST
• URL: http://localhost:8080/payments/process
• Headers: Content-Type: application/json
• Body (raw JSON):

{
  "orderId": 1,
  "amount": 1000,
  "method": "Card"
}

• Expected Response (201):

{
  "id": 1,
  "orderId": 1,
  "amount": 1000,
  "method": "Card",
  "status": "SUCCESS"
}

Step 3: Add an Item

• Method: POST
• URL: http://localhost:8080/items
• Headers: Content-Type: application/json
• Body (raw JSON):

{
  "name": "Tablet"
}

• Expected Response (201):

{
  "message": "Item added: Tablet"
}

Step 4: Verify Data

• Get all items: GET http://localhost:8080/items
• Get all orders: GET http://localhost:8080/orders
• Get all payments: GET http://localhost:8080/payments

---

Docker Images

All services use optimized Docker images:

Service	Base Image	Optimizations
API Gateway	node:20-alpine	Alpine Linux, production-only deps
Item Service	python:3.11-slim	Slim image, no-cache pip install
Order Service	python:3.11-slim	Slim image, no-cache pip install
Payment Service	mcr.microsoft.com/dotnet/aspnet:8.0	Multi-stage build, SDK not in final image

---

Useful Docker Commands

# Build and start all services
docker-compose up --build

# Start in detached mode (background)
docker-compose up --build -d

# View running containers
docker ps

# View logs for a specific service
docker-compose logs item-service
docker-compose logs order-service
docker-compose logs payment-service
docker-compose logs api-gateway

# Stop all services
docker-compose down

# Rebuild a single service
docker-compose build payment-service