[Microservices] 마이크로서비스 패턴 완벽 가이드 — 개요부터 실전(Java·Docker·K8s)까지

1Order Service DB    <-- 독립
2Payment Service DB  <-- 독립
3Shipping Service DB <-- 독립

1Client → API Gateway → Order Service
2                     → Payment Service
3                     → Shipping Service

1try {
2    paymentService.pay(order);
3} catch (ServiceUnavailableException e) {
4    fallbackPayment(order); // 캐시/기본값/지연 큐 등 의미 있는 대체
5}

1Order → Payment → Shipping
2  실패 → Payment 취소 → Order 취소

1OrderCreatedEvent → Payment Service → PaymentProcessedEvent → Shipping Service

1microservice-app/
2├── order-service/      (src/, database/)
3├── payment-service/    (src/, database/)
4├── shipping-service/   (src/, database/)
5└── api-gateway/        (src/)

 1public class Order {
 2    private final String id;
 3    private final String customerId;
 4    private final List<OrderItem> items = new ArrayList<>();
 5    private String status = "PENDING";
 6
 7    public void addItem(String productId, int quantity) {
 8        items.add(new OrderItem(productId, quantity));
 9    }
10
11    public void confirm() { status = "CONFIRMED"; }
12}

1public class PaymentService {
2    public boolean pay(Order order, String method) {
3        if (!order.getStatus().equals("CONFIRMED")) {
4            throw new IllegalStateException("결제 전 주문만 처리 가능");
5        }
6        return true; // 실제 결제 로직
7    }
8}

1public class OrderCreatedEvent {
2    private final String orderId;
3    public OrderCreatedEvent(String orderId) { this.orderId = orderId; }
4}

 1// 주문 생성 → 결제 → 배송
 2OrderService.createOrder(order);
 3eventBus.publish(new OrderCreatedEvent(order.getId()));
 4
 5// PaymentService subscribes OrderCreatedEvent
 6//   → 결제 성공 시 PaymentCompletedEvent 발행
 7//   → 실패 시 OrderCancelledEvent 발행 (보상 트랜잭션)
 8
 9// ShippingService subscribes PaymentCompletedEvent
10//   → 배송 처리

1FROM openjdk:17-jdk-slim
2WORKDIR /app
3COPY target/order-service.jar .
4ENTRYPOINT ["java", "-jar", "order-service.jar"]

 1version: '3'
 2services:
 3  order-service:
 4    build: ./order-service
 5    ports: ["8081:8081"]
 6    networks: [micro-net]
 7  payment-service:
 8    build: ./payment-service
 9    ports: ["8082:8082"]
10    networks: [micro-net]
11  shipping-service:
12    build: ./shipping-service
13    ports: ["8083:8083"]
14    networks: [micro-net]
15networks:
16  micro-net:

 1apiVersion: apps/v1
 2kind: Deployment
 3metadata:
 4  name: order-service
 5spec:
 6  replicas: 2
 7  selector:
 8    matchLabels:
 9      app: order-service
10  template:
11    metadata:
12      labels:
13        app: order-service
14    spec:
15      containers:
16        - name: order-service
17          image: order-service:latest
18          ports:
19            - containerPort: 8081