Saga Design Pattern - Choreography

This project demonstrates the Saga Choreography pattern using Spring Boot and Kafka.
It simulates an Order workflow across multiple microservices with event-driven communication.

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🚀 Microservices in the Project

1. Order Service

   • Accepts order requests from clients.
   • Creates orders in PENDING state.
   • Publishes OrderCreatedEvent.

2. Inventory Service

   • Consumes OrderCreatedEvent.
   • Reserves product stock if available.
   • Publishes:
     • InventoryReservedEvent (success)
     • InventoryFailedEvent (failure)

3. Payment Service

   • Consumes InventoryReservedEvent.
   • Processes payment.
   • Publishes:
     • PaymentCompletedEvent (success)
     • PaymentFailedEvent (failure → triggers inventory release)

4. Shipping Service

   • Consumes PaymentCompletedEvent.
   • Prepares shipping.
   • Publishes OrderShippedEvent.

5. Order Service Compensation

   • Consumes:
     • InventoryFailedEvent → updates order as CANCELLED
     • PaymentFailedEvent → updates order as CANCELLED
     • OrderShippedEvent → updates order as COMPLETED

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🛠 Event Flow

1. Client → Order Service

   • API call: POST /orders
   • Order status = PENDING
   • Publishes OrderCreatedEvent

2. OrderCreatedEvent → Inventory Service

   • If stock available → Publishes InventoryReservedEvent
   • If stock not available → Publishes InventoryFailedEvent

3. InventoryReservedEvent → Payment Service

   • If payment successful → Publishes PaymentCompletedEvent
   • If payment failed → Publishes PaymentFailedEvent

4. PaymentCompletedEvent → Shipping Service

   • Shipping prepared → Publishes OrderShippedEvent

5. Failure Handling

   • InventoryFailedEvent → Order Service updates status to CANCELLED
   • PaymentFailedEvent → Order Service updates status to CANCELLED and Inventory Service releases stock

6. Success Handling

   • OrderShippedEvent → Order Service updates status to COMPLETED

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📌 Topics Used in Kafka

• order-created
• inventory-reserved
• inventory-failed
• payment-completed
• payment-failed
• order-shipped

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✅ Final Outcome

• Happy Path → Order moves through all services → status becomes COMPLETED.
• Failure Path → Any failure (Inventory or Payment) → order becomes CANCELLED.

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⚡ Tech Stack

• Java 19
• Spring Boot 3
• Spring Kafka
• MySQL (Order DB)
• Docker / Docker Compose
• Apache Kafka & Zookeeper

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🔑 Running the Project

1. Start Kafka & Zookeeper using Docker.
2. Run all microservices (Order, Inventory, Payment, Shipping).
3. Place an order via Order Service API.
4. Observe the choreographed events in Kafka topics.

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👨‍💻 Author

Neelu Sahai