[FEAT] 스터디룸 입장 비관적 락 적용 및 동시성 테스트

Author: lehojun

src/main/java/com/example/be/repository/RoomRepository.java

@@ -1,8 +1,20 @@
 package com.example.be.repository;
 
 import com.example.be.domain.Room;
+import jakarta.persistence.LockModeType;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Lock;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 public interface RoomRepository extends JpaRepository<Room,Long> {
     Room findByTitle(String title);
+
+    /**
+     * 비관적 락을 사용하여 Room 조회
+     * 동시에 여러 사용자가 입장할 때 참여자 수 정합성 보장
+     */
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
+    @Query("SELECT r FROM Room r WHERE r.title = :title")
+    Room findByTitleWithLock(@Param("title") String title);
 }

src/main/java/com/example/be/web/controller/OpenviduController.java

@@ -79,15 +79,17 @@ public ResponseEntity<String> receiveWebhook(@RequestHeader("Authorization") Str
                         }
                     }
                     case "participant_joined" -> {
-                        Room room = roomRepository.findByTitle(roomName);
+                        // 비관적 락을 사용하여 동시성 제어
+                        Room room = roomRepository.findByTitleWithLock(roomName);
                         if (room != null) {
                                 room.setParticipantCount(room.getParticipantCount()+1);
                                 roomRepository.save(room);
                                 log.info("Participant joined. Current count: {}", room.getParticipantCount());
                         }
                     }
                     case "participant_left" -> {
-                        Room room = roomRepository.findByTitle(roomName);
+                        // 비관적 락을 사용하여 동시성 제어
+                        Room room = roomRepository.findByTitleWithLock(roomName);
                         if (room != null) {
                             if (room.getParticipantCount() <= 1) {
                                 roomRepository.delete(room);