⚡️ [Improve] 좋아요 기능 성능 개선 및 db 동기화

backend-board/src/main/java/com/backendboard/BackendBoardApplication.java

@@ -3,7 +3,9 @@
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.data.jpa.repository.config.EnableJpaAuditing;
+import org.springframework.scheduling.annotation.EnableScheduling;
 
+@EnableScheduling
 @EnableJpaAuditing
 @SpringBootApplication
 public class BackendBoardApplication {

backend-board/src/main/java/com/backendboard/domain/post/scheduler/PostScheduler.java

@@ -0,0 +1,39 @@
+package com.backendboard.domain.post.scheduler;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.stereotype.Component;
+
+import com.backendboard.domain.postlike.repository.PostLikeRedisRepository;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@Component
+@RequiredArgsConstructor
+public class PostScheduler {
+	private static final String UPDATE_LIKE_COUNT_SQL = "UPDATE post SET like_count = ? WHERE id = ?";
+
+	private final PostLikeRedisRepository postLikeRedisRepository;
+	private final JdbcTemplate jdbcTemplate;
+
+	@Scheduled(fixedDelay = 300_000)
+	public void syncLikeCount() {
+		Map<Object, Object> entries = postLikeRedisRepository.getEntries();
+		List<Object[]> batchArgs = new ArrayList<>();
+
+		for (Map.Entry<Object, Object> entry : entries.entrySet()) {
+			String postId = (String)entry.getKey();
+			long likeCount = ((Number)entry.getValue()).longValue();
+			batchArgs.add(new Object[] {likeCount, Long.valueOf(postId)});
+		}
+
+		jdbcTemplate.batchUpdate(UPDATE_LIKE_COUNT_SQL, batchArgs);
+		postLikeRedisRepository.delete();
+	}
+}

backend-board/src/main/java/com/backendboard/domain/postlike/repository/PostLikeRedisRepository.java

@@ -0,0 +1,13 @@
+package com.backendboard.domain.postlike.repository;
+
+import java.util.Map;
+
+public interface PostLikeRedisRepository {
+	Long getCount(String postId);
+
+	void save(String postId, Long likeCount);
+
+	void delete();
+
+	Map<Object, Object> getEntries();
+}

backend-board/src/main/java/com/backendboard/domain/postlike/repository/PostLikeRedisRepositoryImpl.java

@@ -0,0 +1,41 @@
+package com.backendboard.domain.postlike.repository;
+
+import java.util.Map;
+import java.util.Optional;
+
+import org.springframework.data.redis.core.RedisTemplate;
+import org.springframework.stereotype.Repository;
+
+import lombok.RequiredArgsConstructor;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@Repository
+@RequiredArgsConstructor
+public class PostLikeRedisRepositoryImpl implements PostLikeRedisRepository {
+	private static final String KEY = "post:like";
+
+	private final RedisTemplate<String, Object> redisTemplate;
+
+	@Override
+	public Long getCount(String postId) {
+		return Optional.ofNullable(redisTemplate.opsForHash().get(KEY, postId))
+			.map(value -> ((Number)value).longValue())
+			.orElse(null);
+	}
+
+	@Override
+	public void save(String postId, Long likeCount) {
+		redisTemplate.opsForHash().put(KEY, postId, likeCount);
+	}
+
+	@Override
+	public void delete() {
+		redisTemplate.delete(KEY);
+	}
+
+	@Override
+	public Map<Object, Object> getEntries() {
+		return redisTemplate.opsForHash().entries(KEY);
+	}
+}

backend-board/src/main/java/com/backendboard/domain/postlike/service/PostLikeServiceImpl.java

@@ -6,6 +6,7 @@
 import com.backendboard.domain.postlike.dto.PostLikeCountResponse;
 import com.backendboard.domain.postlike.dto.PostLikeStatusResponse;
 import com.backendboard.domain.postlike.entity.PostLike;
+import com.backendboard.domain.postlike.repository.PostLikeRedisRepository;
 import com.backendboard.domain.postlike.repository.PostLikeRepository;
 import com.backendboard.domain.user.entity.User;
 import com.backendboard.domain.user.repository.UserRepository;
@@ -16,6 +17,7 @@
 @Service
 @RequiredArgsConstructor
 public class PostLikeServiceImpl implements PostLikeService {
+	private final PostLikeRedisRepository postLikeRedisRepository;
 	private final PostLikeRepository postLikeRepository;
 	private final UserRepository userRepository;
 
@@ -41,7 +43,13 @@ public PostLikeStatusResponse getLikeStatus(Long authUserId, Long postId) {
 
 	@Override
 	public PostLikeCountResponse getLikeCount(Long postId) {
-		Long count = postLikeRepository.countByPostId(postId);
+		String postIdKey = postId.toString();
+		Long count = postLikeRedisRepository.getCount(postIdKey);
+
+		if (count == null) {
+			count = postLikeRepository.countByPostId(postId);
+			postLikeRedisRepository.save(postIdKey, count);
+		}
 		return PostLikeCountResponse.toDto(count);
 	}
 }

backend-board/src/main/java/com/backendboard/global/config/RedisConfig.java

@@ -25,9 +25,14 @@ public RedisConnectionFactory redisConnectionFactory() {
 	@Bean
 	public RedisTemplate<String, Object> redisTemplate() {
 		RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
+		StringRedisSerializer stringRedisSerializer = new StringRedisSerializer();
+		GenericJackson2JsonRedisSerializer genericSerializer = new GenericJackson2JsonRedisSerializer();
+
 		redisTemplate.setConnectionFactory(redisConnectionFactory());
-		redisTemplate.setKeySerializer(new StringRedisSerializer());
-		redisTemplate.setValueSerializer(new GenericJackson2JsonRedisSerializer());
+		redisTemplate.setKeySerializer(stringRedisSerializer);
+		redisTemplate.setHashKeySerializer(stringRedisSerializer);
+		redisTemplate.setValueSerializer(genericSerializer);
+		redisTemplate.setHashValueSerializer(genericSerializer);
 		return redisTemplate;
 	}
 }