[volume-7] 이벤트 기반 아키텍처 및 Kafka 파이프라인 구현

apps/commerce-api/build.gradle.kts

@@ -2,6 +2,7 @@ dependencies {
     // add-ons
     implementation(project(":modules:jpa"))
     implementation(project(":modules:redis"))
+    implementation(project(":modules:kafka"))
     implementation(project(":supports:jackson"))
     implementation(project(":supports:logging"))
     implementation(project(":supports:monitoring"))

apps/commerce-api/src/main/java/com/loopers/application/OutboxEventHelper.java

@@ -0,0 +1,18 @@
+package com.loopers.application;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class OutboxEventHelper {
+
+    private OutboxEventHelper() {
+    }
+
+    public static String toJson(ObjectMapper objectMapper, Object value) {
+        try {
+            return objectMapper.writeValueAsString(value);
+        } catch (JsonProcessingException e) {
+            throw new RuntimeException("Outbox payload 직렬화 실패", e);
+        }
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/coupon/CouponFacade.java

@@ -1,10 +1,20 @@
 package com.loopers.application.coupon;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.loopers.application.OutboxEventHelper;
 import com.loopers.domain.coupon.Coupon;
+import com.loopers.domain.coupon.CouponIssueRequest;
+import com.loopers.domain.coupon.CouponIssueRequestRepository;
 import com.loopers.domain.coupon.CouponService;
 import com.loopers.domain.coupon.CouponTemplate;
 import com.loopers.domain.coupon.CouponTemplateService;
+import com.loopers.domain.outbox.OutboxEvent;
+import com.loopers.domain.outbox.OutboxEventRepository;
+import com.loopers.support.error.CoreException;
+import com.loopers.support.error.ErrorMessage;
+import com.loopers.support.error.ErrorType;
 import java.util.List;
+import java.util.Map;
 import lombok.RequiredArgsConstructor;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
@@ -15,11 +25,14 @@ public class CouponFacade {
 
     private final CouponTemplateService couponTemplateService;
     private final CouponService couponService;
+    private final CouponIssueRequestRepository couponIssueRequestRepository;
+    private final OutboxEventRepository outboxEventRepository;
+    private final ObjectMapper objectMapper;
 
     @Transactional
     public CouponTemplateInfo createCouponTemplate(CreateCouponTemplateCommand command) {
         CouponTemplate template = couponTemplateService.create(
-            command.name(), command.discountType(), command.discountValue(), command.minOrderAmount(), command.expiredAt()
+            command.name(), command.discountType(), command.discountValue(), command.minOrderAmount(), command.expiredAt(), command.maxIssuanceCount()
         );
         return CouponTemplateInfo.from(template);
     }
@@ -63,4 +76,36 @@ public List<CouponInfo> getMyCoupons(Long userId) {
             .map(CouponInfo::from)
             .toList();
     }
+
+    @Transactional
+    public CouponIssueRequestInfo requestCouponIssue(Long userId, Long templateId) {
+        couponTemplateService.getById(templateId); // 템플릿 존재 여부 확인
+
+        CouponIssueRequest request = CouponIssueRequest.create(userId, templateId);
+        CouponIssueRequest saved = couponIssueRequestRepository.save(request);
+
+        outboxEventRepository.save(OutboxEvent.create(
+            "coupon-issue-requests",
+            OutboxEventHelper.toJson(objectMapper, Map.of(
+                "requestId", saved.getId(),
+                "userId", userId,
+                "templateId", templateId
+            )),
+            String.valueOf(templateId)
+        ));
+
+        return CouponIssueRequestInfo.from(saved);
+    }
+
+    @Transactional(readOnly = true)
+    public CouponIssueRequestInfo getCouponIssueRequest(Long userId, Long requestId) {
+        CouponIssueRequest request = couponIssueRequestRepository.findById(requestId)
+            .orElseThrow(() -> new CoreException(ErrorType.NOT_FOUND, ErrorMessage.Coupon.COUPON_ISSUE_REQUEST_NOT_FOUND));
+
+        if (!request.getUserId().equals(userId)) {
+            throw new CoreException(ErrorType.NOT_FOUND, ErrorMessage.Coupon.COUPON_ISSUE_REQUEST_NOT_FOUND);
+        }
+
+        return CouponIssueRequestInfo.from(request);
+    }
 }

apps/commerce-api/src/main/java/com/loopers/application/coupon/CouponIssueRequestInfo.java

@@ -0,0 +1,20 @@
+package com.loopers.application.coupon;
+
+import com.loopers.domain.coupon.CouponIssueRequest;
+import com.loopers.domain.coupon.CouponIssueRequestStatus;
+
+public record CouponIssueRequestInfo(
+    Long requestId,
+    Long templateId,
+    CouponIssueRequestStatus status,
+    String failReason
+) {
+    public static CouponIssueRequestInfo from(CouponIssueRequest request) {
+        return new CouponIssueRequestInfo(
+            request.getId(),
+            request.getTemplateId(),
+            request.getStatus(),
+            request.getFailReason()
+        );
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/coupon/CouponTemplateInfo.java

@@ -10,7 +10,9 @@ public record CouponTemplateInfo(
     DiscountType discountType,
     Integer discountValue,
     Integer minOrderAmount,
-    ZonedDateTime expiredAt
+    ZonedDateTime expiredAt,
+    Integer maxIssuanceCount,
+    Integer issuedCount
 ) {
     public static CouponTemplateInfo from(CouponTemplate template) {
         return new CouponTemplateInfo(
@@ -19,7 +21,9 @@ public static CouponTemplateInfo from(CouponTemplate template) {
             template.getType(),
             template.getDiscountValue(),
             template.getMinOrderAmount().value(),
-            template.getExpiredAt()
+            template.getExpiredAt(),
+            template.getMaxIssuanceCount(),
+            template.getIssuedCount()
         );
     }
 }

apps/commerce-api/src/main/java/com/loopers/application/coupon/CreateCouponTemplateCommand.java

@@ -8,6 +8,7 @@ public record CreateCouponTemplateCommand(
     DiscountType discountType,
     Integer discountValue,
     Integer minOrderAmount,
-    ZonedDateTime expiredAt
+    ZonedDateTime expiredAt,
+    Integer maxIssuanceCount
 ) {
 }

apps/commerce-api/src/main/java/com/loopers/application/like/LikeEventListener.java

@@ -0,0 +1,34 @@
+package com.loopers.application.like;
+
+import com.loopers.domain.like.LikedEvent;
+import com.loopers.domain.like.UnlikedEvent;
+import com.loopers.domain.product.ProductService;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class LikeEventListener {
+
+    private final ProductService productService;
+
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    public void handleLiked(LikedEvent event) {
+        log.info("좋아요 이벤트 수신. productId={}", event.getProductId());
+        productService.increaseLikeCount(event.getProductId());
+    }
+
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    public void handleUnliked(UnlikedEvent event) {
+        log.info("좋아요 취소 이벤트 수신. productId={}", event.getProductId());
+        productService.decreaseLikeCount(event.getProductId());
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/like/LikeFacade.java

@@ -1,8 +1,17 @@
 package com.loopers.application.like;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.loopers.application.OutboxEventHelper;
+import com.loopers.domain.like.LikeAction;
+import com.loopers.domain.like.LikedEvent;
 import com.loopers.domain.like.LikeService;
-import com.loopers.domain.product.ProductService;
+import com.loopers.domain.like.UnlikedEvent;
+import com.loopers.domain.outbox.OutboxEvent;
+import com.loopers.domain.outbox.OutboxEventRepository;
+import java.time.ZonedDateTime;
+import java.util.Map;
 import lombok.RequiredArgsConstructor;
+import org.springframework.context.ApplicationEventPublisher;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
@@ -12,15 +21,30 @@
 public class LikeFacade {
 
     private final LikeService likeService;
-    private final ProductService productService;
+    private final ApplicationEventPublisher eventPublisher;
+    private final OutboxEventRepository outboxEventRepository;
+    private final ObjectMapper objectMapper;
 
-    public void toggleLike(Long productId, Long userId) {
+    public LikeAction toggleLike(Long productId, Long userId) {
         if (likeService.isLiked(productId, userId)) {
             likeService.unlike(productId, userId);
-            productService.decreaseLikeCount(productId);
+            eventPublisher.publishEvent(new UnlikedEvent(productId));
+            outboxEventRepository.save(OutboxEvent.create(
+                "catalog-events",
+                OutboxEventHelper.toJson(objectMapper, Map.of("type", "UNLIKED", "productId", productId, "occurredAt", ZonedDateTime.now().toString())),
+                String.valueOf(productId)
+            ));
+            return LikeAction.UNLIKED;
         } else {
             likeService.like(productId, userId);
-            productService.increaseLikeCount(productId);
+            eventPublisher.publishEvent(new LikedEvent(productId));
+            outboxEventRepository.save(OutboxEvent.create(
+                "catalog-events",
+                OutboxEventHelper.toJson(objectMapper, Map.of("type", "LIKED", "productId", productId, "occurredAt", ZonedDateTime.now().toString())),
+                String.valueOf(productId)
+            ));
+            return LikeAction.LIKED;
         }
     }
+
 }

apps/commerce-api/src/main/java/com/loopers/application/logging/UserActionLogListener.java

@@ -0,0 +1,34 @@
+package com.loopers.application.logging;
+
+import com.loopers.domain.like.ProductLikedEvent;
+import com.loopers.domain.like.ProductUnlikedEvent;
+import com.loopers.domain.order.OrderRequestedEvent;
+import com.loopers.domain.product.ProductViewedEvent;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.context.event.EventListener;
+import org.springframework.stereotype.Component;
+
+@Slf4j
+@Component
+public class UserActionLogListener {
+
+    @EventListener
+    public void handleProductViewed(ProductViewedEvent event) {
+        log.info("상품 조회. productId={}", event.getProductId());
+    }
+
+    @EventListener
+    public void handleProductLiked(ProductLikedEvent event) {
+        log.info("좋아요. productId={}, userId={}", event.getProductId(), event.getUserId());
+    }
+
+    @EventListener
+    public void handleProductUnliked(ProductUnlikedEvent event) {
+        log.info("좋아요 취소. productId={}, userId={}", event.getProductId(), event.getUserId());
+    }
+
+    @EventListener
+    public void handleOrderRequested(OrderRequestedEvent event) {
+        log.info("주문 요청. userId={}", event.getUserId());
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/order/OrderConfirmedEventListener.java

@@ -0,0 +1,37 @@
+package com.loopers.application.order;
+
+import com.loopers.domain.coupon.CouponTemplate;
+import com.loopers.domain.coupon.CouponService;
+import com.loopers.domain.coupon.CouponTemplateService;
+import com.loopers.domain.order.OrderConfirmedEvent;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.event.TransactionPhase;
+import org.springframework.transaction.event.TransactionalEventListener;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class OrderConfirmedEventListener {
+
+    private final CouponTemplateService couponTemplateService;
+    private final CouponService couponService;
+
+    @Value("${app.order-confirmed-coupon-template-id:1}")
+    private Long couponTemplateId;
+
+    @Transactional(propagation = Propagation.REQUIRES_NEW)
+    @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
+    public void handle(OrderConfirmedEvent event) {
+        log.info("주문 확정 이벤트 수신. orderId={}, userId={}", event.getOrderId(), event.getUserId());
+
+        CouponTemplate template = couponTemplateService.getById(couponTemplateId);
+        couponService.issue(event.getUserId(), template);
+
+        log.info("쿠폰 발급 완료. userId={}, templateId={}", event.getUserId(), couponTemplateId);
+    }
+}

apps/commerce-api/src/main/java/com/loopers/application/outbox/OutboxRelayScheduler.java

@@ -0,0 +1,32 @@
+package com.loopers.application.outbox;
+
+import com.loopers.domain.outbox.OutboxEvent;
+import com.loopers.domain.outbox.OutboxEventRepository;
+import java.util.List;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.kafka.core.KafkaTemplate;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class OutboxRelayScheduler {
+
+    private final OutboxEventRepository outboxEventRepository;
+    private final KafkaTemplate<Object, Object> kafkaTemplate;
+
+    @Scheduled(fixedDelay = 5000)
+    public void relay() {
+        List<OutboxEvent> unpublished = outboxEventRepository.findUnpublished();
+        for (OutboxEvent event : unpublished) {
+            try {
+                kafkaTemplate.send(event.getEventType(), event.getPartitionKey(), event.getPayload());
+                outboxEventRepository.markPublished(event.getId());
+            } catch (Exception e) {
+                log.error("Failed to publish outbox event. id={}, eventType={}", event.getId(), event.getEventType(), e);
+            }
+        }
+    }
+}