Spring Kafka Microservices - SAGA Pattern with Kafka Streams

3-service microservices system implementing distributed SAGA orchestration using Kafka Streams.

Quick Start

# 1. Start Docker (Kafka + Zookeeper)
docker-compose up -d

# 2. Start all services
./start.sh

# 3. Create test order
curl -X POST http://localhost:8081/api/orders \
  -H "Content-Type: application.json" \
  -d '{
    "customerId": "CUST-001",
    "items": [
      {"productId": "PROD-001", "productName": "Laptop", "quantity": 2, "price": 1000.00}
    ]
  }'

Documentation

📖 ARCHITECTURE.md - Complete architecture, flow diagrams, and implementation details

📖 KAFKA-STREAMS-IMPLEMENTATION.md - Deep dive into Kafka Streams setup

Services

• order-service (8081) - Order management + Kafka Streams orchestrator
• payment-service (8082) - Payment processing
• stock-service (8083) - Inventory management

Key Technology

• Kafka Streams - KStream-KStream joins with 10-second time windows
• SAGA Pattern - Distributed transaction coordination
• Event-Driven - Kafka topics for inter-service communication
• Exactly-Once Semantics - Reliable processing with RocksDB state store

Architecture Overview

User → Order Service → Kafka (order-created)
                         ↓
            ┌────────────┴────────────┐
            ▼                         ▼
      Payment Service          Stock Service
            │                         │
            ▼                         ▼
    Kafka (payment-events)   Kafka (stock-events)
            │                         │
            └────────┬────────────────┘
                     ▼
        ⭐ KAFKA STREAMS JOIN ⭐
         (OrderStreamProcessor)
                     │
                     ▼
          Kafka (order-events)
                     │
        ┌────────────┼────────────┐
        ▼            ▼            ▼
   Order Svc    Payment Svc   Stock Svc
   (Update)     (Confirm/     (Confirm/
   (Status)      Rollback)     Release)

Testing

Run all SAGA test scenarios:

./test-orders.sh

Tests 5 scenarios: CONFIRMED, REJECTED, ROLLBACK (payment fails), ROLLBACK (stock fails), multi-item orders.

Logs

tail -f logs/order-service.log    # Kafka Streams join logs
tail -f logs/payment-service.log
tail -f logs/stock-service.log

Kafka UI

Browse topics and messages: http://localhost:8080