refactor : 알림/채팅 Redis 발행 안정성 및 예외 처리 개선

src/main/java/org/swyp/linkit/domain/chat/redis/RedisChatSubscriber.java

@@ -15,7 +15,7 @@
 public class RedisChatSubscriber implements MessageListener {
 
     private final SimpMessagingTemplate messagingTemplate;
-    private final ObjectMapper objectMapper = new ObjectMapper();
+    private final ObjectMapper objectMapper;
 
     @Override
     public void onMessage(Message message, byte[] pattern) {

src/main/java/org/swyp/linkit/domain/chat/service/ChatService.java

@@ -37,7 +37,7 @@ public class ChatService {
     private final UserRepository userRepository;
     private final StringRedisTemplate redisTemplate;
     private final NotificationService notificationService;
-    private final ObjectMapper objectMapper = new ObjectMapper();
+    private final ObjectMapper objectMapper;
 
     private static final String CHAT_CHANNEL_PREFIX = "chat:room:";
 
@@ -189,8 +189,9 @@ public void deleteMessages(Long roomId, Long userId, List<Long> messageIds) {
      * Redis Pub/Sub을 통해 메시지 발행
      */
     public void publishToRedis(ChatMessage message) {
+        Long roomId = message.getChatRoom().getId();
         ChatPayloadResponseDto payload = ChatPayloadResponseDto.builder()
-                .roomId(message.getChatRoom().getId())
+                .roomId(roomId)
                 .messageId(message.getId())
                 .senderId(message.getSenderId())
                 .senderRole(message.getSenderRole().name())
@@ -203,11 +204,12 @@ public void publishToRedis(ChatMessage message) {
 
         try {
             String json = objectMapper.writeValueAsString(payload);
-            String channel = CHAT_CHANNEL_PREFIX + message.getChatRoom().getId();
+            String channel = CHAT_CHANNEL_PREFIX + roomId;
             redisTemplate.convertAndSend(channel, json);
             log.info("Redis 메시지 발행: channel={}, messageId={}", channel, message.getId());
         } catch (JsonProcessingException e) {
-            log.error("ChatPayload 직렬화 실패", e);
+            log.error("채팅 메시지 직렬화 실패: roomId={}, messageId={}", roomId, message.getId(), e);
+            throw new ChatPublishFailedException(roomId);
         }
     }
 
@@ -228,7 +230,8 @@ public void publishReadEvent(Long roomId, Long userId, Long lastReadMessageId) {
             redisTemplate.convertAndSend(channel, json);
             log.info("읽음 이벤트 발행: channel={}, readerId={}", channel, userId);
         } catch (JsonProcessingException e) {
-            log.error("읽음 이벤트 직렬화 실패", e);
+            log.error("읽음 이벤트 직렬화 실패: roomId={}, userId={}", roomId, userId, e);
+            throw new ChatPublishFailedException(roomId);
         }
     }
 

src/main/java/org/swyp/linkit/domain/notification/dto/NotificationMessageDto.java

@@ -15,7 +15,7 @@
  * WebSocket으로 전송되는 알림 메시지 DTO
  */
 @Getter
-@NoArgsConstructor(access = AccessLevel.PROTECTED)
+@NoArgsConstructor
 @AllArgsConstructor(access = AccessLevel.PRIVATE)
 @Builder(access = AccessLevel.PRIVATE)
 public class NotificationMessageDto {

src/main/java/org/swyp/linkit/domain/notification/service/NotificationServiceImpl.java

@@ -7,6 +7,8 @@
 import org.springframework.data.redis.core.StringRedisTemplate;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.support.TransactionSynchronization;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
 import org.swyp.linkit.domain.notification.dto.NotificationDto;
 import org.swyp.linkit.domain.notification.dto.NotificationMessageDto;
 import org.swyp.linkit.domain.notification.dto.response.ChatRoomUnreadCountResponseDto;
@@ -20,6 +22,7 @@
 import org.swyp.linkit.global.error.exception.NotificationAccessDeniedException;
 import org.swyp.linkit.global.error.exception.NotificationAlreadyReadException;
 import org.swyp.linkit.global.error.exception.NotificationNotFoundException;
+import org.swyp.linkit.global.error.exception.NotificationPublishFailedException;
 import org.swyp.linkit.global.error.exception.UserNotFoundException;
 
 import java.time.LocalDateTime;
@@ -260,18 +263,33 @@ private User findUserById(Long userId) {
     }
 
     /**
-     * Redis Pub/Sub을 통해 알림 발행
+     * Redis Pub/Sub을 통해 알림 발행 (트랜잭션 커밋 이후 발행)
      */
     private void publishNotificationToRedis(Notification notification, String senderNickname, String message) {
         NotificationMessageDto payload = NotificationMessageDto.from(notification, senderNickname, message);
+        String channel = NOTIFICATION_CHANNEL_PREFIX + notification.getReceiver().getId();
+
+        if (TransactionSynchronizationManager.isActualTransactionActive()) {
+            TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronization() {
+                @Override
+                public void afterCommit() {
+                    doPublish(channel, payload, notification.getId());
+                }
+            });
+        } else {
+            doPublish(channel, payload, notification.getId());
+        }
+    }
 
+    private void doPublish(String channel, NotificationMessageDto payload, Long notificationId) {
         try {
             String json = objectMapper.writeValueAsString(payload);
-            String channel = NOTIFICATION_CHANNEL_PREFIX + notification.getReceiver().getId();
             redisTemplate.convertAndSend(channel, json);
-            log.info("Redis 알림 발행: channel={}, notificationId={}", channel, notification.getId());
+            log.info("Redis 알림 발행: channel={}, notificationId={}", channel, notificationId);
         } catch (JsonProcessingException e) {
-            log.error("알림 직렬화 실패", e);
+            // afterCommit() 내부에서는 예외를 throw해도 Spring이 억제하므로 로그로 대체
+            NotificationPublishFailedException ex = new NotificationPublishFailedException(notificationId);
+            log.error("[{}] {}", ex.getErrorCode().getCode(), ex.getMessage(), e);
         }
     }
 
@@ -283,7 +301,7 @@ private String generateNotificationMessage(NotificationType type, String senderN
             case REQUEST_RECEIVED -> senderNickname + "님이 스킬 교환을 요청했습니다.";
             case REQUEST_SENT -> senderNickname + "님에게 스킬 교환 요청을 보냈습니다.";
             case REQUEST_STATUS_CHANGED -> "스킬 교환 요청 상태가 변경되었습니다.";
-            case CHAT_MESSAGE -> senderNickname + "님에게 메시지 요청이 왔습니다.";
+            case CHAT_MESSAGE -> senderNickname + "님이 메시지를 보냈습니다.";
         };
     }
 }

src/main/java/org/swyp/linkit/global/error/ErrorCode.java

@@ -135,6 +135,9 @@ public enum ErrorCode implements BaseErrorCode {
     @ExplainError("멘토와 멘티가 동일한 사용자인 경우 발생합니다.")
     CHAT_SAME_USER(HttpStatus.BAD_REQUEST, "CH006", "멘토와 멘티는 서로 다른 사용자여야 합니다."),
 
+    @ExplainError("Redis Pub/Sub을 통한 채팅 메시지 발행에 실패한 경우 발생합니다.")
+    CHAT_PUBLISH_FAILED(HttpStatus.INTERNAL_SERVER_ERROR, "CH007", "채팅 메시지 발행에 실패했습니다."),
+
     // 크레딧
     @ExplainError("사용자의 크레딧 정보가 존재하지 않는 경우 발생합니다.")
     NOT_FOUND_CREDIT(HttpStatus.NOT_FOUND, "CR001", "크레딧 정보를 찾을 수 없습니다."),
@@ -216,6 +219,9 @@ public enum ErrorCode implements BaseErrorCode {
     @ExplainError("지원하지 않는 알림 타입을 요청한 경우 발생합니다.")
     INVALID_NOTIFICATION_TYPE(HttpStatus.BAD_REQUEST, "N004", "유효하지 않은 알림 타입입니다."),
 
+    @ExplainError("Redis Pub/Sub을 통한 알림 발행에 실패한 경우 발생합니다.")
+    NOTIFICATION_PUBLISH_FAILED(HttpStatus.INTERNAL_SERVER_ERROR, "N005", "알림 발행에 실패했습니다."),
+
     // 채팅 파일 업로드
     @ExplainError("채팅 파일 크기가 10MB를 초과하는 경우 발생합니다.")
     CHAT_FILE_SIZE_EXCEEDED(HttpStatus.BAD_REQUEST, "CF001", "파일 용량은 최대 10MB까지 업로드할 수 있습니다."),

src/main/java/org/swyp/linkit/global/error/exception/ChatPublishFailedException.java

@@ -0,0 +1,16 @@
+package org.swyp.linkit.global.error.exception;
+
+import org.swyp.linkit.global.error.ErrorCode;
+import org.swyp.linkit.global.error.exception.base.BusinessException;
+
+public class ChatPublishFailedException extends BusinessException {
+
+    public ChatPublishFailedException() {
+        super(ErrorCode.CHAT_PUBLISH_FAILED);
+    }
+
+    public ChatPublishFailedException(Long roomId) {
+        super(ErrorCode.CHAT_PUBLISH_FAILED,
+                "채팅 메시지 발행에 실패했습니다. roomId=" + roomId);
+    }
+}

src/main/java/org/swyp/linkit/global/error/exception/NotificationPublishFailedException.java

@@ -0,0 +1,16 @@
+package org.swyp.linkit.global.error.exception;
+
+import org.swyp.linkit.global.error.ErrorCode;
+import org.swyp.linkit.global.error.exception.base.BusinessException;
+
+public class NotificationPublishFailedException extends BusinessException {
+
+    public NotificationPublishFailedException() {
+        super(ErrorCode.NOTIFICATION_PUBLISH_FAILED);
+    }
+
+    public NotificationPublishFailedException(Long notificationId) {
+        super(ErrorCode.NOTIFICATION_PUBLISH_FAILED,
+                "알림 발행에 실패했습니다. notificationId=" + notificationId);
+    }
+}

src/main/java/org/swyp/linkit/global/swagger/docs/ChatExceptionDocs.java

@@ -59,4 +59,11 @@ public BaseErrorCode getErrorCode() {
             return ErrorCode.CHAT_SAME_USER;
         }
     }
+
+    public static class ChatPublishFailedException implements SwaggerExampleExceptions {
+        @Override
+        public BaseErrorCode getErrorCode() {
+            return ErrorCode.CHAT_PUBLISH_FAILED;
+        }
+    }
 }

src/main/java/org/swyp/linkit/global/swagger/docs/NotificationExceptionDocs.java

@@ -45,4 +45,11 @@ public BaseErrorCode getErrorCode() {
             return ErrorCode.INVALID_NOTIFICATION_TYPE;
         }
     }
+
+    public static class NotificationPublishFailedException implements SwaggerExampleExceptions {
+        @Override
+        public BaseErrorCode getErrorCode() {
+            return ErrorCode.NOTIFICATION_PUBLISH_FAILED;
+        }
+    }
 }