[BE] DB read, write 쿼리 트래픽을 분리해요 (#360)

* chore: 서브모듈 변경사항 반영

* feat: `@Transactional` readOnly 설정 별 DB 트랜잭션 분산 로직 추가

* feat: 읽기 쿼리에 대해 `@Transactional` readOnly 설정 추가

* refactor(DataSourceConfig): `Map.of()` 수정

backend/src/main/java/kr/momo/config/DataSourceConfig.java

@@ -0,0 +1,56 @@
+package kr.momo.config;
+
+import java.util.Map;
+import javax.sql.DataSource;
+import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.boot.jdbc.DataSourceBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Primary;
+import org.springframework.context.annotation.Profile;
+import org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy;
+
+@Configuration
+@Profile("prod")
+public class DataSourceConfig {
+
+    public static final String SOURCE_SERVER = "source";
+    public static final String REPLICA_SERVER = "replica";
+
+    @Bean(SOURCE_SERVER)
+    @ConfigurationProperties(prefix = "spring.datasource.source")
+    public DataSource sourceDataSource() {
+        return DataSourceBuilder.create()
+                .build();
+    }
+
+    @Bean(REPLICA_SERVER)
+    @ConfigurationProperties(prefix = "spring.datasource.replica")
+    public DataSource replicaDataSource() {
+        return DataSourceBuilder.create()
+                .build();
+    }
+
+    @Bean
+    public DataSource routingDataSource(
+            @Qualifier(SOURCE_SERVER) DataSource source,
+            @Qualifier(REPLICA_SERVER) DataSource replica
+    ) {
+        RoutingDataSource routingDataSource = new RoutingDataSource();
+        Map<Object, Object> dataSourceMap = Map.of(
+                SOURCE_SERVER, source,
+                REPLICA_SERVER, replica
+        );
+        routingDataSource.setTargetDataSources(dataSourceMap);
+        routingDataSource.setDefaultTargetDataSource(source);
+        return routingDataSource;
+    }
+
+    @Bean
+    @Primary
+    public DataSource dataSource() {
+        DataSource dataSource = routingDataSource(sourceDataSource(), replicaDataSource());
+        return new LazyConnectionDataSourceProxy(dataSource);
+    }
+}

backend/src/main/java/kr/momo/config/RoutingDataSource.java

@@ -0,0 +1,15 @@
+package kr.momo.config;
+
+import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+public class RoutingDataSource extends AbstractRoutingDataSource {
+
+    @Override
+    protected Object determineCurrentLookupKey() {
+        if (TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
+            return DataSourceConfig.REPLICA_SERVER;
+        }
+        return DataSourceConfig.SOURCE_SERVER;
+    }
+}

backend/src/main/java/kr/momo/service/attendee/AttendeeService.java

@@ -49,6 +49,7 @@ private AttendeeLoginResponse signup(Meeting meeting, AttendeeName name, Attende
         return AttendeeLoginResponse.from(jwtManager.generate(attendee.getId()), attendee);
     }
 
+    @Transactional(readOnly = true)
     public List<String> findAll(String uuid) {
         Meeting meeting = meetingRepository.findByUuid(uuid)
                 .orElseThrow(() -> new MomoException(MeetingErrorCode.INVALID_UUID));