透過訂單處理流程，練習 RabbitMQ 核心概念與最佳實踐的 Spring Boot 微服務專案。
| 目標 | 說明 |
|---|---|
| Producer / Consumer 解耦 | 服務間透過message queue通訊，互不依賴 |
| 非同步流程 | 訂單、付款、庫存非同步處理 |
| 消息重送與死信 | 實現 DLX (Dead Letter Exchange) |
| 冪等性控制 | 確保重複訊息不造成重複處理 |
| 水平擴展 | 支援多個 Consumer 競爭消費 |
[客戶端]
│ POST /api/orders
▼
[Order Service] ──→ order.exchange ──→ order.queue
│
[Payment Service]
│ payment.exchange
▼
inventory.queue
│
[Inventory Service × N]
(多實例競爭消費)
| 服務 | 角色 | Port |
|---|---|---|
order-service |
Producer：建立訂單，發布 OrderCreatedEvent |
8081 |
payment-service |
Consumer + Producer：處理付款，發布 PaymentCompletedEvent |
8082 |
inventory-service |
Consumer：扣減庫存，支援多實例水平擴展 | 8083 |
Exchanges & Queues:
order.exchange (topic)
└─ routing: order.created → order.queue
│ 失敗
order.dlx.exchange → order.dlq
payment.exchange (topic)
└─ routing: payment.completed → inventory.queue
│ 失敗
inventory.dlx.exchange → inventory.dlq
mq-practice/
├── docker-compose.yml
├── order-service/
│ └── src/main/java/com/example/order/
│ ├── controller/ # OrderController
│ ├── service/ # OrderService
│ ├── entity/ # Order, OrderItem
│ ├── mq/ # OrderEventPublisher, RabbitConfig
│ └── dto/event/ # OrderCreatedEvent
├── payment-service/
│ └── src/main/java/com/example/payment/
│ ├── application/service/ # PaymentService
│ ├── entity/ # Payment, IdempotencyRecord
│ ├── mq/listener/ # OrderEventListener
│ ├── mq/publisher/ # PaymentEventPublisher
│ └── dto/event/ # OrderCreatedEvent, PaymentCompletedEvent
└── inventory-service/
└── src/main/java/com/example/inventory/
├── service/ # InventoryService（樂觀鎖扣庫存）
├── entity/ # Inventory（@Version）, IdempotencyRecord
├── mq/listener/ # PaymentEventListener（concurrency: 2-5）
└── dto/event/ # PaymentCompletedEvent
1. 啟動 RabbitMQ
docker-compose up -d rabbitmq2. 啟動各服務
# 各服務獨立啟動
cd order-service && mvn spring-boot:run
cd payment-service && mvn spring-boot:run
cd inventory-service && mvn spring-boot:run
# 或啟動多個 Inventory 實例進行水平擴展測試
docker-compose up --scale inventory-service=33. 建立訂單
curl -X POST http://localhost:8081/api/orders \
-H "Content-Type: application/json" \
-d '{
"customerId": "C001",
"items": [
{"productId": "P001", "quantity": 2, "price": 100.00}
]
}'4. 查看 RabbitMQ Management UI
http://localhost:15672
帳號: guest / 密碼: guest
@RabbitListener(queues = "order.queue")
public void handleOrderCreated(OrderCreatedEvent event, Channel channel,
@Header(AmqpHeaders.DELIVERY_TAG) long tag) {
try {
if (retryCount >= 3) {
channel.basicNack(tag, false, false); // 超過重試次數 → DLQ
return;
}
paymentService.processPayment(event);
channel.basicAck(tag, false);
} catch (RecoverableException e) {
channel.basicNack(tag, false, true); // 可重試，重新入隊
} catch (Exception e) {
channel.basicNack(tag, false, false); // 不可重試 → DLQ
}
}@Transactional
public void processPayment(OrderCreatedEvent event) {
// 已處理過則直接跳過
if (idempotencyRepository.findByEventId(event.getEventId())
.filter(r -> "PROCESSED".equals(r.getStatus())).isPresent()) {
return;
}
// 插入 PROCESSING 紀錄，防止並發重複處理
idempotencyRepository.save(new IdempotencyRecord(event.getEventId(), "PROCESSING"));
// 業務邏輯...
record.setStatus("PROCESSED");
}@Entity
public class Inventory {
private String productId;
private Integer quantity;
@Version // 並發扣庫存時，version 不符會拋出 OptimisticLockException
private Long version;
}# inventory-service application.yml
spring:
rabbitmq:
listener:
simple:
acknowledge-mode: manual
prefetch: 10 # 每個 consumer 一次最多取 10 筆
concurrency: 2 # 最小 2 個 worker thread
max-concurrency: 5 # 最大 5 個 worker thread正常流程:
客戶端 → Order Service (建立訂單) → order.queue
→ Payment Service (處理付款) → inventory.queue
→ Inventory Service (扣減庫存) ✅
失敗流程:
Payment 失敗 → NACK (requeue) → 最多重試 3 次 → order.dlq → 人工介入
庫存不足 → NACK (不 requeue) → inventory.dlq → 人工介入
冪等性:
重複訊息 (eventId: E001) → 查 idempotency_record → 已 PROCESSED → 直接 ACK，跳過
- Order Service（建立訂單 + MQ Publisher）
- Payment Service（MQ Consumer + 冪等性 + Publisher）
- Inventory Service Phase 1（基礎結構）
- Inventory Service Phase 2（MQ Consumer + DLX + 重試分流）
- Inventory Service Phase 3（冪等性機制）
- Inventory Service Phase 4（多實例消費 + 樂觀鎖並發控制）
- 加入監控和結構化日誌
- 壓力測試與調優
- Language: Java 17
- Framework: Spring Boot 3
- Message Broker: RabbitMQ
- Database: H2 (in-memory)
- Build: Maven
- Container: Docker / Docker Compose