EventFlow Order Service

System 1 in the EventFlow event-driven architecture demo.

A FastAPI service that accepts customer orders via REST API and publishes OrderCreated events to Azure Service Bus for downstream processing.

Architecture Role

User → [Order Service] → Azure Service Bus → [Payment Service]
              ↓
       Application Insights

Features

• REST API for order creation and retrieval
• Event publishing to Azure Service Bus
• International currency support (USD, EUR, GBP, JPY, etc.)
• Health check and readiness endpoints
• Structured logging with correlation IDs
• OpenTelemetry instrumentation for Azure Monitor

Tech Stack

• Python 3.11+
• FastAPI
• Azure Service Bus SDK
• OpenTelemetry + Azure Monitor
• Pydantic v2 for data validation

Local Development

# Install dependencies
pip install poetry
poetry install

# Set environment variables
cp .env.example .env
# Edit .env with your values

# Run the service
poetry run uvicorn app.main:app --reload --port 8001

# Run tests
poetry run pytest -v

Environment Variables

Variable	Description	Default
AZURE_SERVICEBUS_CONNECTION_STRING	Service Bus connection string	(required)
AZURE_SERVICEBUS_QUEUE_NAME	Queue name for order events	order-events
APPLICATIONINSIGHTS_CONNECTION_STRING	App Insights connection string	(optional)
LOG_LEVEL	Logging level	INFO
ENVIRONMENT	Deployment environment	development

API Endpoints

Method	Path	Description
POST	/api/orders	Create a new order
GET	/api/orders/{order_id}	Get order by ID
GET	/api/orders	List recent orders
GET	/health	Health check
GET	/ready	Readiness check (verifies Service Bus connectivity)

Event Schema

Published to Azure Service Bus as JSON:

{
  "event_id": "uuid",
  "event_type": "OrderCreated",
  "timestamp": "2026-01-15T10:30:00Z",
  "data": {
    "order_id": "uuid",
    "customer_id": "cust-123",
    "currency": "USD",
    "amount": 4999,
    "items": [
      {
        "product_id": "prod-456",
        "name": "Widget",
        "quantity": 2,
        "unit_price": 2499
      }
    ]
  }
}

Note: amount is always in the smallest currency unit (cents for USD/EUR, yen for JPY). The downstream Payment Service is responsible for interpreting the amount based on the currency's decimal places.

Docker

docker build -t eventflow-order-service .
docker run -p 8001:8001 --env-file .env eventflow-order-service