[Feature] Config Server, Database per Service, Circuit Breaker 구현

.env.example

@@ -0,0 +1,11 @@
+# MySQL Database Credentials
+# IMPORTANT: Copy this file to .env and change the values before deploying!
+# cp .env.example .env
+
+# MySQL Root Password
+# Use a strong password with at least 16 characters including uppercase, lowercase, numbers, and special characters
+MYSQL_ROOT_PASSWORD=your-strong-root-password-here
+
+# MySQL User Password
+# Use a strong password with at least 16 characters including uppercase, lowercase, numbers, and special characters
+MYSQL_USER_PASSWORD=your-strong-user-password-here

api-gateway/build.gradle

@@ -5,4 +5,7 @@ plugins {
 dependencies {
     implementation 'org.springframework.cloud:spring-cloud-starter-gateway'
     implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client'
+    implementation 'org.springframework.cloud:spring-cloud-starter-config'  // Config Client
+    implementation 'org.springframework.cloud:spring-cloud-starter-circuitbreaker-reactor-resilience4j'  // Circuit Breaker
+    implementation 'org.springframework.boot:spring-boot-starter-actuator'  // Health check
 }

api-gateway/src/main/java/com/example/gateway/FallbackController.java

@@ -0,0 +1,62 @@
+package com.example.gateway;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.time.LocalDateTime;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Circuit Breaker가 OPEN 상태일 때 실행되는 Fallback 컨트롤러
+ * 서비스 장애 시 사용자에게 적절한 응답 제공
+ */
+@RestController
+@RequestMapping("/fallback")
+public class FallbackController {
+    private static final Logger log = LoggerFactory.getLogger(FallbackController.class);
+
+    /**
+     * User Service 장애 시 Fallback 응답
+     */
+    @GetMapping("/user-service")
+    public ResponseEntity<Map<String, Object>> userServiceFallback() {
+        return createFallbackResponse("user-service",
+            "User 서비스가 일시적으로 사용 불가능합니다. 잠시 후 다시 시도해주세요.");
+    }
+
+    /**
+     * Order Service 장애 시 Fallback 응답
+     */
+    @GetMapping("/order-service")
+    public ResponseEntity<Map<String, Object>> orderServiceFallback() {
+        return createFallbackResponse("order-service",
+            "Order 서비스가 일시적으로 사용 불가능합니다. 잠시 후 다시 시도해주세요.");
+    }
+
+    /**
+     * 공통 Fallback 응답 생성 메서드
+     *
+     * @param serviceName 서비스 이름
+     * @param message 사용자에게 표시할 메시지
+     * @return Fallback 응답
+     */
+    private ResponseEntity<Map<String, Object>> createFallbackResponse(String serviceName, String message) {
+        log.warn("Circuit breaker activated for service: {}", serviceName);
+
+        Map<String, Object> response = new HashMap<>();
+        response.put("status", "SERVICE_UNAVAILABLE");
+        response.put("message", message);
+        response.put("timestamp", LocalDateTime.now());
+        response.put("service", serviceName);
+
+        return ResponseEntity
+                .status(HttpStatus.SERVICE_UNAVAILABLE)
+                .body(response);
+    }
+}

api-gateway/src/main/resources/application.yml

@@ -1,6 +1,8 @@
 spring:
   application:
     name: api-gateway
+  config:
+    import: optional:configserver:http://localhost:8888
   cloud:
     gateway:
       routes:

build.gradle

@@ -32,8 +32,8 @@ subprojects {
 
     // 공통 의존성
     dependencies {
-        compileOnly 'org.projectlombok:lombok'
-        annotationProcessor 'org.projectlombok:lombok'
+        compileOnly 'org.projectlombok:lombok:1.18.30'  // Java 21 호환 버전
+        annotationProcessor 'org.projectlombok:lombok:1.18.30'
         testImplementation 'org.springframework.boot:spring-boot-starter-test'
     }
 

common/build.gradle

@@ -6,4 +6,13 @@ dependencies {
     implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
     compileOnly 'org.projectlombok:lombok'
     annotationProcessor 'org.projectlombok:lombok'
+}
+
+// common은 라이브러리 모듈이므로 bootJar 비활성화
+bootJar {
+    enabled = false  // 실행 가능한 JAR 만들지 않음
+}
+
+jar {
+    enabled = true  // 일반 라이브러리 JAR만 생성
 }

config-server/Dockerfile

@@ -0,0 +1,33 @@
+# Multi-stage build for optimization
+FROM gradle:8.5-jdk21 AS builder
+WORKDIR /app
+
+# Copy Gradle files
+COPY build.gradle settings.gradle ./
+COPY gradle ./gradle
+
+# Copy source code
+COPY config-server ./config-server
+
+# Build the application
+RUN gradle :config-server:bootJar --no-daemon
+
+# Runtime stage
+FROM eclipse-temurin:21-jre
+WORKDIR /app
+
+# Install curl for healthcheck
+RUN apt-get update && \
+    apt-get install -y curl && \
+    apt-get clean && \
+    rm -rf /var/lib/apt/lists/*
+
+# Create non-root user for security
+RUN addgroup --system spring && adduser --system --ingroup spring spring
+USER spring:spring
+
+# Copy JAR from builder
+COPY --from=builder /app/config-server/build/libs/*.jar app.jar
+
+EXPOSE 8888
+ENTRYPOINT ["java", "-jar", "app.jar"]

config-server/build.gradle

@@ -0,0 +1,9 @@
+plugins {
+    id 'org.springframework.boot' version '3.1.5'
+}
+
+dependencies {
+    implementation 'org.springframework.cloud:spring-cloud-config-server'
+    implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client'
+    implementation 'org.springframework.boot:spring-boot-starter-actuator'
+}

config-server/src/main/java/com/example/configserver/ConfigServerApplication.java

@@ -0,0 +1,13 @@
+package com.example.configserver;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.config.server.EnableConfigServer;
+
+@SpringBootApplication
+@EnableConfigServer  // Config Server 활성화
+public class ConfigServerApplication {
+    public static void main(String[] args) {
+        SpringApplication.run(ConfigServerApplication.class, args);
+    }
+}

config-server/src/main/resources/application-docker.yml

@@ -0,0 +1,31 @@
+server:
+  port: 8888
+
+spring:
+  application:
+    name: config-server
+  cloud:
+    config:
+      server:
+        native:
+          search-locations: classpath:/config
+
+management:
+  endpoints:
+    web:
+      exposure:
+        include: health,info
+  endpoint:
+    health:
+      show-details: always
+
+eureka:
+  client:
+    service-url:
+      defaultZone: http://eureka-server:8761/eureka/  # Docker 환경용
+  instance:
+    prefer-ip-address: true
+
+logging:
+  level:
+    org.springframework.cloud.config: DEBUG

config-server/src/main/resources/application.yml

@@ -0,0 +1,33 @@
+server:
+  port: 8888  # Config Server 포트
+
+spring:
+  application:
+    name: config-server
+  profiles:
+    active: native  # 파일 시스템 기반 설정 사용 (Git도 가능)
+  cloud:
+    config:
+      server:
+        native:
+          search-locations: classpath:/config  # 설정 파일 위치
+
+management:
+  endpoints:
+    web:
+      exposure:
+        include: health,info
+  endpoint:
+    health:
+      show-details: always
+
+eureka:
+  client:
+    service-url:
+      defaultZone: http://localhost:8761/eureka/
+  instance:
+    prefer-ip-address: true
+
+logging:
+  level:
+    org.springframework.cloud.config: DEBUG

config-server/src/main/resources/config/api-gateway.yml

@@ -0,0 +1,71 @@
+server:
+  port: 8080
+
+spring:
+  cloud:
+    gateway:
+      routes:
+        # User Service 라우팅
+        - id: user-service
+          uri: lb://user-service  # lb = load balanced (Eureka로 찾기)
+          predicates:
+            - Path=/api/users/**
+          filters:
+            - name: CircuitBreaker
+              args:
+                name: userServiceCircuitBreaker
+                fallbackUri: forward:/fallback/user-service
+            - RewritePath=/api/users/(?<segment>.*), /$\{segment}
+
+        # Order Service 라우팅
+        - id: order-service
+          uri: lb://order-service
+          predicates:
+            - Path=/api/orders/**
+          filters:
+            - name: CircuitBreaker
+              args:
+                name: orderServiceCircuitBreaker
+                fallbackUri: forward:/fallback/order-service
+            - RewritePath=/api/orders/(?<segment>.*), /$\{segment}
+
+      discovery:
+        locator:
+          enabled: true
+          lower-case-service-id: true
+
+eureka:
+  client:
+    service-url:
+      defaultZone: http://localhost:8761/eureka/
+  instance:
+    prefer-ip-address: true
+
+# Resilience4j Circuit Breaker 설정
+resilience4j:
+  circuitbreaker:
+    configs:
+      default:
+        registerHealthIndicator: true
+        slidingWindowSize: 10  # 최근 10개 요청 기준으로 판단
+        minimumNumberOfCalls: 5  # 최소 5번 호출 후 동작
+        failureRateThreshold: 50  # 실패율 50% 이상이면 OPEN
+        waitDurationInOpenState: 10000  # OPEN 상태에서 10초 대기
+        permittedNumberOfCallsInHalfOpenState: 3  # HALF_OPEN에서 3번 테스트
+        slowCallDurationThreshold: 2000  # 2초 이상이면 느린 호출
+        slowCallRateThreshold: 50  # 느린 호출 50% 이상이면 OPEN
+    instances:
+      userServiceCircuitBreaker:
+        baseConfig: default
+      orderServiceCircuitBreaker:
+        baseConfig: default
+
+  timelimiter:
+    configs:
+      default:
+        timeoutDuration: 3s  # 3초 타임아웃
+
+logging:
+  level:
+    org.springframework.cloud.gateway: DEBUG
+    io.github.resilience4j: DEBUG

config-server/src/main/resources/config/order-service.yml

@@ -0,0 +1,35 @@
+server:
+  port: 8082
+
+spring:
+  datasource:
+    url: jdbc:mysql://mysql-order:3306/orderdb?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC
+    driverClassName: com.mysql.cj.jdbc.Driver
+    username: user
+    password: password
+
+  jpa:
+    hibernate:
+      ddl-auto: update
+    show-sql: true
+    properties:
+      hibernate:
+        dialect: org.hibernate.dialect.MySQLDialect
+        format_sql: true
+
+eureka:
+  client:
+    service-url:
+      defaultZone: http://localhost:8761/eureka/
+  instance:
+    prefer-ip-address: true
+
+logging:
+  level:
+    com.example: DEBUG
+
+# 추가 설정: 비즈니스 로직 관련
+app:
+  order:
+    max-order-amount: 1000000
+    delivery-fee: 3000