Edit: 게시글 좋아요 및 댓글 수 동시성 문제 해결 및 테스트

src/main/java/swyp/team5/greening/comment/service/CommentCommandService.java

@@ -17,8 +17,6 @@
 import swyp.team5.greening.post.domain.repository.PostRepository;
 import swyp.team5.greening.post.exception.PostExceptionMessage;
 
-//todo: 댓글 추가나 삭제를 통해 발생하는 댓글 수 증감 -> 이벤트 처리
-//todo: 동시성 문제 처리
 @Service
 @RequiredArgsConstructor
 public class CommentCommandService {
@@ -34,7 +32,7 @@ public SaveCommentResponseDto saveComment(
     ) {
         //게시물 존재 조회
         Post post = postRepository
-                .findByIdAndState(requestDto.postId(), PostState.IN_PROGRESS)
+                .findByIdAndStateWithLock(requestDto.postId(), PostState.IN_PROGRESS)
                 .orElseThrow(() ->
                         new GreeningGlobalException(PostExceptionMessage.NOT_FOUND_POST));
 
@@ -82,7 +80,7 @@ public void deleteComment(
                         CommentExceptionMessage.NOT_FOUND_COMMENT));
 
         //게시물 존재 조회
-        Post post = postRepository.findByIdAndState(comment.getPostId(), PostState.IN_PROGRESS)
+        Post post = postRepository.findByIdAndStateWithLock(comment.getPostId(), PostState.IN_PROGRESS)
                 .orElseThrow(() ->
                         new GreeningGlobalException(PostExceptionMessage.NOT_FOUND_POST));
 
@@ -91,11 +89,11 @@ public void deleteComment(
             throw new GreeningGlobalException(CommentExceptionMessage.BAD_REQUEST_COMMENT_WRITER);
         }
 
-        //게시물 댓글 수 감소
-        post.decreaseCommentCount();
-
         //댓글 삭제
         commentRepository.deleteById(requestDto.commentId());
+
+        //게시물 댓글 수 감소
+        post.decreaseCommentCount();
     }
 
 }

src/main/java/swyp/team5/greening/post/domain/repository/PostRepository.java

@@ -14,4 +14,6 @@ public interface PostRepository {
 
     Optional<Post> findByIdAndState(Long postId, PostState state);
 
+    Optional<Post> findByIdAndStateWithLock(Long postId, PostState state);
+
 }

src/main/java/swyp/team5/greening/post/infrastructure/PostJpaRepository.java

@@ -1,9 +1,27 @@
 package swyp.team5.greening.post.infrastructure;
 
+import jakarta.persistence.LockModeType;
+import java.util.Optional;
 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;
 import swyp.team5.greening.post.domain.entity.Post;
+import swyp.team5.greening.post.domain.entity.PostState;
 import swyp.team5.greening.post.domain.repository.PostRepository;
 
 public interface PostJpaRepository extends JpaRepository<Post, Long>, PostRepository {
 
+    @Lock(LockModeType.PESSIMISTIC_WRITE)
+    @Query("""
+            SELECT post
+            FROM Post post
+            WHERE post.id = :postId
+            AND post.state = :state
+            """)
+    Optional<Post> findByIdAndStateWithLock(
+            @Param("postId") Long postId,
+            @Param("state") PostState state
+    );
+
 }

src/main/java/swyp/team5/greening/postLike/service/PostLikeCommandService.java

@@ -13,8 +13,6 @@
 import swyp.team5.greening.postLike.domain.repository.LikeRepository;
 import swyp.team5.greening.postLike.dto.PostLikeResponseDto;
 
-//todo: 게시글 좋아요 수 상태 변화 -> 이벤트 처리
-//todo: 동시성 문제 처리
 @Service
 @RequiredArgsConstructor
 public class PostLikeCommandService {
@@ -26,7 +24,7 @@ public class PostLikeCommandService {
     @Transactional
     public PostLikeResponseDto likeOrCancel(Long userId, Long postId) {
         //게시글 조회
-        Post post = postRepository.findByIdAndState(postId, PostState.IN_PROGRESS)
+        Post post = postRepository.findByIdAndStateWithLock(postId, PostState.IN_PROGRESS)
                 .orElseThrow(
                         () -> new GreeningGlobalException(PostExceptionMessage.NOT_FOUND_POST));
 

src/test/java/swyp/team5/greening/comment/service/CommentCommandServiceTest.java

@@ -71,7 +71,7 @@ class saveCommentTest {
         @DisplayName("사용자는 게시물에 댓글을 작성할 수 있다. 이 때 게시물의 댓글 수가 증가한다.")
         void testCase1() {
             //given
-            given(postRepository.findByIdAndState(postId, PostState.IN_PROGRESS)).willReturn(
+            given(postRepository.findByIdAndStateWithLock(postId, PostState.IN_PROGRESS)).willReturn(
                     Optional.of(postEntity));
             given(commentRepository.save(any(Comment.class))).willReturn(commentEntity);
             ReflectionTestUtils.setField(postEntity, "id", postId);
@@ -82,7 +82,7 @@ void testCase1() {
                     userId, new SaveCommentRequestDto(postId, comment));
 
             //then
-            verify(postRepository).findByIdAndState(postId, PostState.IN_PROGRESS);
+            verify(postRepository).findByIdAndStateWithLock(postId, PostState.IN_PROGRESS);
             verify(commentRepository).save(any(Comment.class));
             assertThat(responseDto.id()).isEqualTo(commentEntity.getId());
             assertThat(postEntity.getCommentCount()).isEqualTo(1L);
@@ -92,7 +92,7 @@ void testCase1() {
         @DisplayName("게시물이 존재하지 않을 경우, 예외가 발생한다.")
         void testCase2() {
             //given
-            given(postRepository.findByIdAndState(postId, PostState.IN_PROGRESS)).willReturn(
+            given(postRepository.findByIdAndStateWithLock(postId, PostState.IN_PROGRESS)).willReturn(
                     Optional.empty());
 
             //when
@@ -170,7 +170,7 @@ void testCase2() {
         @DisplayName("댓글 삭제할 수 있다. 이 때 게시글의 댓글 수는 감소한다.")
         void testCase3() {
             //given
-            given(postRepository.findByIdAndState(postId, PostState.IN_PROGRESS)).willReturn(
+            given(postRepository.findByIdAndStateWithLock(postId, PostState.IN_PROGRESS)).willReturn(
                     Optional.of(postEntity));
             given(commentRepository.findById(commentId)).willReturn(Optional.of(testComment));
 

src/test/java/swyp/team5/greening/comment/service/PostCommentCountConcurrencyTest.java

@@ -0,0 +1,86 @@
+package swyp.team5.greening.comment.service;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import swyp.team5.greening.comment.domain.repository.CommentRepository;
+import swyp.team5.greening.comment.dto.request.SaveCommentRequestDto;
+import swyp.team5.greening.post.domain.entity.Post;
+import swyp.team5.greening.post.domain.entity.PostState;
+import swyp.team5.greening.post.domain.repository.PostRepository;
+import swyp.team5.greening.support.TestContainerSupport;
+
+@SpringBootTest
+public class PostCommentCountConcurrencyTest extends TestContainerSupport {
+
+    @Autowired
+    private CommentCommandService commentCommandService;
+
+    @Autowired
+    private CommentRepository commentRepository;
+
+    @Autowired
+    private PostRepository postRepository;
+
+    @BeforeEach
+    void init() {
+        commentRepository.deleteAll();
+        postRepository.deleteAll();
+    }
+
+    @Nested
+    @DisplayName("게시글 1개가 존재한다.")
+    class TestCase1 {
+
+        Post post;
+
+        @BeforeEach
+        void init() {
+            post = Post.builder()
+                    .title("제목")
+                    .commentCount(0L)
+                    .likeCount(0L)
+                    .state(PostState.IN_PROGRESS)
+                    .categoryId(1L)
+                    .userId(1L)
+                    .build();
+            postRepository.save(post);
+        }
+
+        @Test
+        @DisplayName("동시에 20명의 유저가 게시글의 댓글을 작성한다면, 댓글 수는 20이다.")
+        void saveCommentConcurrencyTest() throws InterruptedException {
+            //given
+            ExecutorService executorService = Executors.newCachedThreadPool();
+            CountDownLatch countDownLatch = new CountDownLatch(20);
+
+            //when
+            for (long i = 0; i < 20; i++) {
+                final long userId = i;
+                executorService.submit(() -> {
+                    commentCommandService.saveComment(userId,
+                            new SaveCommentRequestDto(
+                                    post.getId(), "댓글" + userId
+                            ));
+
+                    countDownLatch.countDown();
+                });
+            }
+
+            countDownLatch.await();
+
+            Post result = postRepository.findByIdAndState(post.getId(), PostState.IN_PROGRESS)
+                    .orElseThrow();
+
+            assertThat(result.getCommentCount()).isEqualTo(20L);
+        }
+    }
+}

src/test/java/swyp/team5/greening/postLike/service/PostLikeCommandServiceTest.java

@@ -52,7 +52,7 @@ class TestCase1 {
         @DisplayName("게시글을 좋아요 한 상태라면, 좋아요가 취소되며 좋아요 수가 감소한다.")
         void likeCancelTest() {
             //given
-            given(postRepository.findByIdAndState(postId, PostState.IN_PROGRESS)).willReturn(
+            given(postRepository.findByIdAndStateWithLock(postId, PostState.IN_PROGRESS)).willReturn(
                     Optional.of(post));
             ReflectionTestUtils.setField(post, "id", postId);
             given(likeRepository.findByUserIdAndPostId(userId, postId)).willReturn(
@@ -71,7 +71,7 @@ void likeCancelTest() {
         @DisplayName("게시글을 좋아요 하지 않은 상태라면, 좋아요 처리되며 좋아요 수가 증가한ㄷ.")
         void likeTest() {
             //given
-            given(postRepository.findByIdAndState(postId, PostState.IN_PROGRESS)).willReturn(
+            given(postRepository.findByIdAndStateWithLock(postId, PostState.IN_PROGRESS)).willReturn(
                     Optional.of(post));
             ReflectionTestUtils.setField(post, "id", postId);
 

src/test/java/swyp/team5/greening/postLike/service/PostLikeCountConcurrencyTest.java

@@ -0,0 +1,110 @@
+package swyp.team5.greening.postLike.service;
+
+import static org.assertj.core.api.Assertions.*;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import swyp.team5.greening.post.domain.entity.Post;
+import swyp.team5.greening.post.domain.entity.PostState;
+import swyp.team5.greening.post.domain.repository.PostRepository;
+import swyp.team5.greening.postLike.domain.repository.LikeRepository;
+import swyp.team5.greening.support.TestContainerSupport;
+
+@SpringBootTest
+@DisplayName("게시글 좋아요 동시성 테스트")
+class PostLikeCountConcurrencyTest extends TestContainerSupport {
+
+    @Autowired
+    private PostLikeCommandService postLikeCommandService;
+
+    @Autowired
+    private PostRepository postRepository;
+
+    @Autowired
+    private LikeRepository likeRepository;
+
+    @BeforeEach
+    void init() {
+        postRepository.deleteAll();
+        likeRepository.deleteAll();
+    }
+
+    @Nested
+    @DisplayName("게시글 1개가 존재한다.")
+    class TestCase1 {
+
+        Post post;
+
+        @BeforeEach
+        void init() {
+            post = Post.builder()
+                    .title("제목")
+                    .commentCount(0L)
+                    .likeCount(0L)
+                    .state(PostState.IN_PROGRESS)
+                    .categoryId(1L)
+                    .userId(1L)
+                    .build();
+            postRepository.save(post);
+        }
+
+        @Test
+        @DisplayName("동시에 20명의 유저가 게시글을 좋아요 할 경우, 좋아요 수가 알맞게 증가한다.")
+        void likeConcurrencyTest() throws InterruptedException {
+            //given
+            ExecutorService executorService = Executors.newCachedThreadPool();
+            CountDownLatch countDownLatch = new CountDownLatch(20);
+
+            //when
+            for (long i = 0; i < 20; i++) {
+                final long userId = i;
+                executorService.submit(() -> {
+                    postLikeCommandService.likeOrCancel(userId, post.getId());
+                    countDownLatch.countDown();
+                });
+            }
+
+            countDownLatch.await();
+
+            Post result = postRepository.findByIdAndState(post.getId(), PostState.IN_PROGRESS)
+                    .orElseThrow();
+
+            //then
+            assertThat(result.getLikeCount()).isEqualTo(20L);
+
+            executorService.shutdown();
+        }
+
+        @Test
+        @DisplayName("한 명의 유저가 해당 기능을 30번 호출할 경우, 좋아요 수는 0이다.")
+        void likeOrCancelConcurrencyTest() throws InterruptedException {
+            //given
+            ExecutorService executorService = Executors.newCachedThreadPool();
+            CountDownLatch countDownLatch = new CountDownLatch(30);
+
+            //when
+            for (int i = 0; i < 30; i++) {
+                executorService.submit(() -> {
+                    postLikeCommandService.likeOrCancel(1L, post.getId());
+                    countDownLatch.countDown();
+                });
+            }
+
+            countDownLatch.await();
+
+            Post result = postRepository.findByIdAndState(post.getId(), PostState.IN_PROGRESS)
+                    .orElseThrow();
+
+            //then
+            assertThat(result.getLikeCount()).isEqualTo(0L);
+
+        }
+    }
+}