🌀 Saga Design Pattern (Orchestration vs Choreography)

Distributed transaction management using Orchestration and Choreography patterns with MassTransit, RabbitMQ, and Quartz.NET in .NET 9.

Overview

This project demonstrates two approaches to implementing the Saga pattern for managing distributed transactions:

• Orchestration: Central state machine (OrderStateMachine) coordinates all steps
• Choreography: Services react to events independently without central coordination

Both handle an e-commerce order flow: Payment → Inventory → Shipping with full compensation on failures.

Orchestration vs Choreography

Aspect	Orchestration	Choreography
Control	Centralized state machine	Decentralized events
Coordination	Orchestrator manages flow	Services react to events
Compensation	Explicit by orchestrator	Implicit by services
Complexity	Easier to understand	Harder to trace
Timeout	Managed by Quartz.NET	Per-service handling
Best For	Complex workflows	Simple, autonomous services

Technologies

• .NET 9 - Application framework
• MassTransit 8 - Saga state machine & messaging
• RabbitMQ - Message broker
• Quartz.NET - Timeout management (orchestration)
• Docker - Containerization

State Machine (Orchestration)

Flow:

Initial → PaymentProcessing → InventoryReserving → Shipping → Completed
             ↓                      ↓                  ↓
           Failed ←──────────────  Failed  ←────────  Failed

States: Initial, PaymentProcessing, InventoryReserving, Shipping, Completed, Failed

Timeouts: Payment (30s), Inventory (15s), Shipping (60s)

Compensation: On failure, orchestrator triggers refunds and inventory releases

Key Features

Retry Mechanism

cfg.UseMessageRetry(r => r.Interval(3, TimeSpan.FromSeconds(5)));

• 3 retry attempts
• 5-second intervals
• Handles transient failures

Timeout Management (Orchestration)

cfg.UseMessageScheduler(new Uri("queue:quartz"));

Quartz.NET manages timeouts and triggers compensation on expiry.

Getting Started

Quick Start with Docker

# 1. Start RabbitMQ
docker run -d --name rabbitmq -p 5672:5672 -p 15672:15672 rabbitmq:3-management

# 2. Run services
docker-compose up --build

API Endpoints

Create Order - Orchestration:

POST http://localhost:5000/orders/orchestration

Create Order - Choreography:

POST http://localhost:5000/orders/choreography

Response:

{
  "orderId": "3fa85f64-5717-4562-b3fc-2c963f66afa6"
}

Testing Failures

The implementation includes simulated failures:

• Payment: 10% failure rate
• Inventory: 20% failure rate
• Shipping: 5% failure rate

Monitor:

• RabbitMQ Management UI: http://localhost:15672 (guest/guest)
• Application logs for compensation events
• Retry attempts in action

Example Flow:

✅ Success: Order → Payment → Inventory → Shipping → Completed
❌ Failure: Order → Payment → Inventory FAILED → Refund → Failed
⏱️ Timeout: Order → Payment timeout (30s) → Failed

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