[Spring boot] Database가 Replication일 때 DataSource 설정

1. Replication 란?

Master/Slave 관계를 설정하고 데이터 원본은 Master, 데이터 사본은 Slave에 저장한 후 Master에서는 Write(Insert, Update, Delete) 작업을 Slave에서는 Read(Select) 작업을 처리하여 부하를 분산시키는 기술입니다.

2. DataSource 설정

@Transactional(readOnly = true | false) 을 통해 Database Replication일 때 DataSource를 설정할 수 있습니다.
@Transactional(readOnly = false) 일 때는 Master DB에서 처리
@Transactional(readOnly = true) 일 때는 Slavee DB에서 처리

application.yml

spring:
  datasource:
    master:
      hikari:
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://localhost:3306/sample
        read-only: false
        username: sample_user
        password: password1!
    slave:
      hikari:
        driver-class-name: com.mysql.cj.jdbc.Driver
        jdbc-url: jdbc:mysql://localhost:3306/sample
        read-only: true
        username: sample_user
        password: password1!

DataSourceConfig.java

package com.example.datasourcereplication.config;

import com.zaxxer.hikari.HikariDataSource;
import javax.sql.DataSource;
import lombok.extern.slf4j.Slf4j;
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;

@Slf4j
@Configuration
public class DataSourceConfig {

  private final String MASTER_DATA_SOURCE = "masterDataSource";
  private final String SLAVE_DATA_SOURCE = "slaveDataSource";

  @Primary
  @Bean(MASTER_DATA_SOURCE)
  @ConfigurationProperties(prefix = "spring.datasource.master.hikari")
  public DataSource masterDataSource() {
    return DataSourceBuilder
        .create()
        .type(HikariDataSource.class)
        .build();
  }

  @Bean(SLAVE_DATA_SOURCE)
  @ConfigurationProperties(prefix = "spring.datasource.slave.hikari")
  public DataSource slaveDataSource() {
    return DataSourceBuilder
        .create()
        .type(HikariDataSource.class)
        .build();
  }
}

DataSourceType.java
동적으로 DataSource를 변경하려면 AbstractRoutingDataSource.setTargetDataSources(Map<Object, Object> targetDataSources)를 설정이 필요한데, 이때 DataSource를 Map 형태로 전달하기 위해 필요한 key 값을 정의한 enum입니다.

package com.example.datasourcereplication.common.type;

public enum DataSourceType {
  MASTER, SLAVE
}

RoutingDataSource.java
AbstractRoutingDataSource.determineCurrentLookupKey()를 구현할 때 @Transactional(readOnly = true) 여부에 따라서 DataSource를 결정할 수 있도록 구현하세요.

package com.example.datasourcereplication.config;

import com.example.datasourcereplication.common.type.DataSourceType;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import org.springframework.transaction.support.TransactionSynchronizationManager;

public class RoutingDataSource extends AbstractRoutingDataSource {

  @Override
  protected Object determineCurrentLookupKey() {
    return TransactionSynchronizationManager.isCurrentTransactionReadOnly()
        ? DataSourceType.SLAVE : DataSourceType.MASTER;
  }
}

RoutingDataSourceConfig.java
스프링은 트랜잭션에 진입하는 순간 설정된 DataSource에서 Connection을 가져오기 때문에, Multi DataSource 환경에서 트랜잭션에 진입한 이후 DataSource 분기가 불가능합니다.
LazyConnectionDataSourceProxy을 사용하면 실제로 필요한 시점에 DataSource에서 Connection을 가져올 수 있습니다.

package com.example.datasourcereplication.config;

import com.example.datasourcereplication.common.type.DataSourceType;
import java.util.HashMap;
import java.util.Map;
import javax.sql.DataSource;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.jdbc.datasource.LazyConnectionDataSourceProxy;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.JpaVendorAdapter;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;

@Slf4j
@EnableJpaRepositories(
    basePackages = "com.example.datasourcereplication.domain.repository",
    entityManagerFactoryRef = "entityManagerFactory",
    transactionManagerRef = "transactionManager"
)
@Configuration
public class RoutingDataSourceConfig {

  private final String ROUTING_DATA_SOURCE = "routingDataSource";
  private final String MASTER_DATA_SOURCE = "masterDataSource";
  private final String SLAVE_DATA_SOURCE = "slaveDataSource";
  private final String DATA_SOURCE = "dataSource";

  @Bean(ROUTING_DATA_SOURCE)
  public DataSource routingDataSource(
      @Qualifier(MASTER_DATA_SOURCE) final DataSource masterDataSource,
      @Qualifier(SLAVE_DATA_SOURCE) final DataSource slaveDataSource) {

    RoutingDataSource routingDataSource = new RoutingDataSource();

    Map<Object, Object> dataSourceMap = new HashMap<>();
    dataSourceMap.put(DataSourceType.MASTER, masterDataSource);
    dataSourceMap.put(DataSourceType.SLAVE, slaveDataSource);

    routingDataSource.setTargetDataSources(dataSourceMap);
    routingDataSource.setDefaultTargetDataSource(masterDataSource);

    return routingDataSource;
  }

  @Bean(DATA_SOURCE)
  public DataSource dataSource(
      @Qualifier(ROUTING_DATA_SOURCE) DataSource routingDataSource) {
    return new LazyConnectionDataSourceProxy(routingDataSource);
  }

  @Bean("entityManagerFactory")
  public LocalContainerEntityManagerFactoryBean entityManagerFactory(
      @Qualifier(DATA_SOURCE) DataSource dataSource) {
    LocalContainerEntityManagerFactoryBean entityManagerFactory
        = new LocalContainerEntityManagerFactoryBean();
    entityManagerFactory.setDataSource(dataSource);
    entityManagerFactory.setPackagesToScan("com.example.datasourcereplication.domain.entity");
    entityManagerFactory.setJpaVendorAdapter(this.jpaVendorAdapter());
    entityManagerFactory.setPersistenceUnitName("entityManager");
    return entityManagerFactory;
  }

  private JpaVendorAdapter jpaVendorAdapter() {
    HibernateJpaVendorAdapter hibernateJpaVendorAdapter = new HibernateJpaVendorAdapter();
    hibernateJpaVendorAdapter.setGenerateDdl(false);
    hibernateJpaVendorAdapter.setShowSql(false);
    hibernateJpaVendorAdapter.setDatabasePlatform("org.hibernate.dialect.MySQL5InnoDBDialect");
    return hibernateJpaVendorAdapter;
  }

  @Bean("transactionManager")
  public PlatformTransactionManager platformTransactionManager(
      @Qualifier("entityManagerFactory") LocalContainerEntityManagerFactoryBean entityManagerFactory) {
    JpaTransactionManager jpaTransactionManager = new JpaTransactionManager();
    jpaTransactionManager.setEntityManagerFactory(entityManagerFactory.getObject());
    return jpaTransactionManager;
  }
}

3. 단위 테스트

3_1. DataSource 설정 테스트

package com.example.datasourcereplication.config;

import static org.junit.jupiter.api.Assertions.assertEquals;

import com.zaxxer.hikari.HikariDataSource;
import javax.sql.DataSource;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.core.env.Environment;

@Slf4j
@SpringBootTest
class DataSourceConfigTest {

  @Autowired
  private Environment environment;

  @DisplayName("MasterDataSource 설정 테스트")
  @Test
  void masterDataSourceTest(
      @Qualifier("masterDataSource") final DataSource masterDataSource) {

    // Given
    String driverClassName = environment.getProperty("spring.datasource.master.hikari.driver-class-name");
    String jdbcUrl = environment.getProperty("spring.datasource.master.hikari.jdbc-url");
    Boolean readOnly = Boolean.valueOf(environment.getProperty("spring.datasource.master.hikari.read-only"));
    String username = environment.getProperty("spring.datasource.master.hikari.username");

    // When
    try (HikariDataSource hikariDataSource = (HikariDataSource) masterDataSource) {

      // Then
      log.info("hikariDataSource : [{}]", hikariDataSource);
      assertEquals(hikariDataSource.getDriverClassName(), driverClassName);
      assertEquals(hikariDataSource.getJdbcUrl(), jdbcUrl);
      assertEquals(hikariDataSource.isReadOnly(), readOnly);
      assertEquals(hikariDataSource.getUsername(), username);
    }
  }

  @DisplayName("SlaveDataSource 설정 테스트")
  @Test
  void slaveDataSourceTest(
      @Qualifier("slaveDataSource") final DataSource slaveDataSource) {

    // Given
    String driverClassName = environment.getProperty("spring.datasource.slave.hikari.driver-class-name");
    String jdbcUrl = environment.getProperty("spring.datasource.slave.hikari.jdbc-url");
    Boolean readOnly = Boolean.valueOf(environment.getProperty("spring.datasource.slave.hikari.read-only"));
    String username = environment.getProperty("spring.datasource.slave.hikari.username");

    // When
    try (HikariDataSource hikariDataSource = (HikariDataSource) slaveDataSource) {

      // Then
      log.info("hikariDataSource : [{}]", hikariDataSource);
      assertEquals(hikariDataSource.getDriverClassName(), driverClassName);
      assertEquals(hikariDataSource.getJdbcUrl(), jdbcUrl);
      assertEquals(hikariDataSource.isReadOnly(), readOnly);
      assertEquals(hikariDataSource.getUsername(), username);
    }
  }
}

3_2. Replication 설정 테스트

package com.example.datasourcereplication.config;

import static org.junit.jupiter.api.Assertions.assertEquals;

import com.example.datasourcereplication.common.type.DataSourceType;
import java.lang.reflect.Method;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.transaction.annotation.Transactional;

@Slf4j
@SpringBootTest
class RoutingDataSourceConfigTest {

  private static final String DETERMINE_CURRENT_LOOKUP_KEY = "determineCurrentLookupKey";

  @Transactional(readOnly = false)
  @DisplayName("MasterDataSource Replication 설정 테스트")
  @Test
  void testMasterDataSourceReplication() throws Exception {

    // Given
    RoutingDataSource routingDataSource = new RoutingDataSource();

    // When
    Method declaredMethod = RoutingDataSource.class.getDeclaredMethod(DETERMINE_CURRENT_LOOKUP_KEY);
    declaredMethod.setAccessible(true);

    Object object = declaredMethod.invoke(routingDataSource);

    // Then
    log.info("object : [{}]", object);
    assertEquals(DataSourceType.MASTER.toString(), object.toString());
  }

  @Transactional(readOnly = true)
  @DisplayName("SlaveDataSource Replication 설정 테스트")
  @Test
  void testSlaveDataSourceReplication() throws Exception {

    // Given
    RoutingDataSource routingDataSource = new RoutingDataSource();

    // When
    Method declaredMethod = RoutingDataSource.class.getDeclaredMethod(DETERMINE_CURRENT_LOOKUP_KEY);
    declaredMethod.setAccessible(true);

    Object object = declaredMethod.invoke(routingDataSource);

    // Then
    log.info("object : [{}]", object);
    assertEquals(DataSourceType.SLAVE.toString(), object.toString());
  }
}

3_3. Transaction 테스트
TodoServiceTest.testInsertTodoReadOnlyTrue() 실행 시 Exception이 발생하여 정상적으로 롤백되는지 확인하세요.

TodoService.java

package com.example.datasourcereplication.service;

import com.example.datasourcereplication.domain.entity.Todo;
import com.example.datasourcereplication.domain.repository.TodoRepository;
import com.example.datasourcereplication.dto.TodoRequestDto;
import java.util.List;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Slf4j
@RequiredArgsConstructor
@Service
public class TodoService {

  private final TodoRepository todoRepository;

  /**
   * To-Do 한건 저장
   */
  @Transactional(readOnly = false)
  public int insertTodoReadOnlyFalse(TodoRequestDto todoRequest) {

    int result = 0;

    todoRepository.save(Todo.builder()
        .title(todoRequest.getTitle())
        .description(todoRequest.getDescription())
        .completed(todoRequest.getCompleted())
        .build());

    result++;

    return result;
  }

  /**
   * To-Do 한건 저장
   */
  @Transactional(readOnly = true)
  public int insertTodoReadOnlyTrue(TodoRequestDto todoRequest) {

    int result = 0;

    todoRepository.save(Todo.builder()
        .title(todoRequest.getTitle())
        .description(todoRequest.getDescription())
        .completed(todoRequest.getCompleted())
        .build());

    result++;

    return result;
  }
}

 

TodoServiceTest.java

package com.example.datasourcereplication.service;

import static org.junit.jupiter.api.Assertions.assertThrows;

import com.example.datasourcereplication.dto.TodoRequestDto;
import java.util.ArrayList;
import java.util.List;
import javax.annotation.Resource;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;

@Slf4j
@SpringBootTest
class TodoServiceTest {

  @Resource
  TodoService todoService;

  @DisplayName("insertTodo_@Transactional(readOnly = true)일 때 한건 저장")
  @Test
  void testInsertTodoReadOnlyFalse() {

    // Given
    TodoRequestDto todoRequest = TodoRequestDto.builder()
        .title("Title Junit Test Insert 01")
        .description("Description Junit Test Insert 02")
        .completed(false)
        .build();

    // When
    int result = todoService.insertTodoReadOnlyFalse(todoRequest);
    log.info("result:{}", result);

    // Then
    Assertions.assertEquals(1, result);
  }

  @DisplayName("insertTodoReadOnlyTrue_@Transactional(readOnly = true)일 때 한건 저장")
  @Test
  void testInsertTodoReadOnlyTrue() {

    // Given
    TodoRequestDto todoRequest = TodoRequestDto.builder()
        .title("Title Junit Test")
        .description("Description Junit Test")
        .completed(false)
        .build();

    // When & Then
    Exception exception = assertThrows(Exception.class,
        () -> todoService.insertTodoReadOnlyTrue(todoRequest));
    log.info("exception:{}", exception);
  }
}

소스 코드는 Github Repository - https://github.com/tychejin1218/blog/tree/main/datasource-replication 를 참조하세요.