feat: Redis 기반 중복 알림 요청 최적화

k6/notification-dedup.js

@@ -0,0 +1,33 @@
+import http from 'k6/http';
+import { check } from 'k6';
+
+export const options = {
+    vus: 30,
+    duration: '30s',
+};
+
+const BASE_URL = 'http://localhost:8080';
+
+export default function () {
+
+    // 모든 요청이 동일한 eventId
+    const payload = JSON.stringify({
+        eventId: 'dedup-performance-test',
+        userId: 1,
+        channels: ['SMS'],
+    });
+
+    const res = http.post(
+        `${BASE_URL}/api/v1/notifications`,
+        payload,
+        {
+            headers: {
+                'Content-Type': 'application/json',
+            },
+        }
+    );
+
+    check(res, {
+        'status is 202': (r) => r.status === 202,
+    });
+}

src/main/java/com/backendsystemdesignlab/notification/dedup/NotificationDedupCache.java

@@ -0,0 +1,65 @@
+package com.backendsystemdesignlab.notification.dedup;
+
+import com.backendsystemdesignlab.notification.notification.dto.SendNotificationResponse;
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.dao.DataAccessException;
+import org.springframework.data.redis.core.StringRedisTemplate;
+import org.springframework.stereotype.Component;
+import tools.jackson.core.JacksonException;
+import tools.jackson.databind.ObjectMapper;
+
+import java.time.Duration;
+import java.util.Optional;
+
+@Component
+@RequiredArgsConstructor
+@Slf4j
+public class NotificationDedupCache {
+
+    private static final String KEY_PREFIX = "notification:dedup:";
+    private static final Duration TTL = Duration.ofHours(24);
+
+    private final StringRedisTemplate redisTemplate;
+    private final ObjectMapper objectMapper;
+
+    public Optional<SendNotificationResponse> find(String eventId) {
+
+        try {
+            String value = redisTemplate.opsForValue().get(KEY_PREFIX + eventId);
+
+            if (value == null) {
+                log.debug("[Dedup MISS] eventId={}", eventId);
+                return Optional.empty();
+            }
+
+            log.debug("[Dedup HIT] eventId={}", eventId);
+
+            return Optional.of(
+                    objectMapper.readValue(
+                            value,
+                            SendNotificationResponse.class
+                    )
+            );
+        } catch (DataAccessException e) {
+            log.warn("[Dedup] Redis 조회 실패. DB로 fallback. eventId={}", eventId);
+            return Optional.empty();
+        } catch (JacksonException e) {
+            log.warn("[Dedup] Redis 데이터 역직렬화 실패. eventId={}", eventId);
+            return Optional.empty();
+        }
+    }
+
+    public void save(String eventId, SendNotificationResponse response) {
+
+        try {
+            String value = objectMapper.writeValueAsString(response);
+            log.debug("[Dedup SAVE] eventId={}", eventId);
+            redisTemplate.opsForValue().set(KEY_PREFIX + eventId, value, TTL);
+        } catch (DataAccessException e) {
+            log.warn("[Dedup] Redis 저장 실패. 캐시 없이 계속 진행. eventId={}", eventId);
+        } catch (JacksonException e) {
+            log.warn("[Dedup] 응답 직렬화 실패. eventId={}", eventId);
+        }
+    }
+}

src/main/java/com/backendsystemdesignlab/notification/notification/service/NotificationService.java

@@ -1,40 +1,57 @@
 package com.backendsystemdesignlab.notification.notification.service;
 
-import com.backendsystemdesignlab.notification.messaging.DeliveryPublisher;
+import com.backendsystemdesignlab.notification.dedup.NotificationDedupCache;
 import com.backendsystemdesignlab.notification.notification.dto.*;
 
 import lombok.RequiredArgsConstructor;
+import org.springframework.dao.DataIntegrityViolationException;
 import org.springframework.stereotype.Service;
 
 @Service
 @RequiredArgsConstructor
 public class NotificationService {
 
     private final NotificationTransactionService transactionService;
-    private final DeliveryPublisher deliveryPublisher;
+    private final NotificationDedupCache dedupCache;
 
     public SendNotificationResponse send(SendNotificationRequest request) {
 
-        // DB 작업
-        PreparedNotification prepared = transactionService.prepare(request);
+        // 1. Redis Fast Path
+        var cached = dedupCache.find(request.eventId());
+
+        if (cached.isPresent()) {
+            return cached.get();
+        }
+
+        // 2. 기존 DB 처리
+        PreparedNotification prepared;
+
+        try {
+            prepared = transactionService.prepare(request);
+        } catch (DataIntegrityViolationException e) {
+            return transactionService.findExisingResponse(request.eventId())
+                    .orElseThrow(() -> e);
+        }
+        SendNotificationResponse response;
 
         // 이미 처리했던 eventId
         if (prepared.alreadyProcessed()) {
             long deliveryCount = transactionService.countDeliveries(prepared.notificationId());
-            return new SendNotificationResponse(
+            response = new SendNotificationResponse(
                     prepared.notificationId(),
                     prepared.status(),
                     deliveryCount
             );
+        } else {
+            response = new SendNotificationResponse(
+                    prepared.notificationId(),
+                    prepared.status(),
+                    prepared.deliveryCount()
+            );
         }
 
-//        deliveryPublisher.publishAll(prepared.notificationId(), prepared.deliveries());
-
-        return new SendNotificationResponse(
-                prepared.notificationId(),
-                prepared.status(), // PROCESSING 비동기 이기 때문에 아직 Provider 전송이 안끝남
-                prepared.deliveryCount()
-        );
+        dedupCache.save(request.eventId(), response);
 
+        return response;
     }
 }

src/main/java/com/backendsystemdesignlab/notification/notification/service/NotificationTransactionService.java

@@ -6,6 +6,7 @@
 import com.backendsystemdesignlab.notification.notification.dto.DeliveryCommand;
 import com.backendsystemdesignlab.notification.notification.dto.PreparedNotification;
 import com.backendsystemdesignlab.notification.notification.dto.SendNotificationRequest;
+import com.backendsystemdesignlab.notification.notification.dto.SendNotificationResponse;
 import com.backendsystemdesignlab.notification.notification.repository.NotificationDeliveryRepository;
 import com.backendsystemdesignlab.notification.notification.repository.NotificationRepository;
 import com.backendsystemdesignlab.notification.outbox.OutboxEvent;
@@ -21,10 +22,7 @@
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
-import java.util.ArrayList;
-import java.util.List;
-import java.util.Set;
-import java.util.UUID;
+import java.util.*;
 import java.util.stream.Collectors;
 
 @Service
@@ -258,4 +256,17 @@ public void recordPublishFinalFailure(Long notificationId, Long deliveryId) {
 
         updateNotificationStatus(notificationId, notification);
     }
+
+    @Transactional(readOnly = true)
+    public Optional<SendNotificationResponse> findExisingResponse(String eventId) {
+        return notificationRepository.findByEventId(eventId)
+                .map(notification -> {
+                    long deliveryCount = deliveryRepository.countByNotificationId(notification.getId());
+                    return new SendNotificationResponse(
+                            notification.getId(),
+                            notification.getStatus(),
+                            deliveryCount
+                    );
+                });
+    }
 }

src/main/resources/application.yml

@@ -36,6 +36,8 @@ spring:
     redis:
       host: ${SPRING_DATA_REDIS_HOST:localhost}
       port: ${SPRING_DATA_REDIS_PORT:6379}
+      connect-timeout: 300ms
+      timeout: 300ms
 
 management:
   endpoints: