DB replication 적용 (#636)

* feat: Replication 기능 추가

* feat: 서버 datasource 추가

backend/baton/src/main/java/touch/baton/config/DataSourceConfig.java

@@ -0,0 +1,55 @@
+package touch.baton.config;
+
+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;
+import touch.baton.infra.database.datasource.DataSourceType;
+import touch.baton.infra.database.datasource.RoutingDataSource;
+
+import javax.sql.DataSource;
+import java.util.Map;
+
+import static touch.baton.infra.database.datasource.DataSourceType.Name.REPLICA_NAME;
+import static touch.baton.infra.database.datasource.DataSourceType.Name.ROUTING_NAME;
+import static touch.baton.infra.database.datasource.DataSourceType.Name.SOURCE_NAME;
+
+@Profile("deploy")
+@Configuration
+public class DataSourceConfig {
+
+    @Qualifier(SOURCE_NAME)
+    @ConfigurationProperties(prefix = "spring.datasource.source")
+    @Bean
+    public DataSource sourceDataSource() {
+        return DataSourceBuilder.create().build();
+    }
+
+    @Qualifier(REPLICA_NAME)
+    @ConfigurationProperties(prefix = "spring.datasource.replica")
+    @Bean
+    public DataSource replicaDataSource() {
+        return DataSourceBuilder.create().build();
+    }
+
+    @Qualifier(ROUTING_NAME)
+    @Bean
+    public DataSource routingDataSource(@Qualifier(SOURCE_NAME) final DataSource sourceDataSource,
+                                        @Qualifier(REPLICA_NAME) final DataSource replicaDataSource
+    ) {
+        return RoutingDataSource.createDefaultSetting(
+                Map.of(DataSourceType.SOURCE, sourceDataSource,
+                        DataSourceType.REPLICA, replicaDataSource)
+        );
+    }
+
+    @Bean
+    @Primary
+    public DataSource dataSource(@Qualifier(ROUTING_NAME) final DataSource replicationRoutingDataSource) {
+        return new LazyConnectionDataSourceProxy(replicationRoutingDataSource);
+    }
+}

backend/baton/src/main/java/touch/baton/infra/database/datasource/DataSourceType.java

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+package touch.baton.infra.database.datasource;
+
+import static touch.baton.infra.database.datasource.DataSourceType.Name.REPLICA_NAME;
+import static touch.baton.infra.database.datasource.DataSourceType.Name.SOURCE_NAME;
+
+public enum DataSourceType {
+
+    SOURCE(SOURCE_NAME),
+    REPLICA(REPLICA_NAME);
+
+    private final String name;
+
+    DataSourceType(final String name) {
+        this.name = name;
+    }
+
+    public static class Name {
+
+        public static final String ROUTING_NAME = "ROUTING";
+        public static final String SOURCE_NAME = "SOURCE";
+        public static final String REPLICA_NAME = "REPLICA";
+    }
+
+}

backend/baton/src/main/java/touch/baton/infra/database/datasource/RoutingDataSource.java

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+package touch.baton.infra.database.datasource;
+
+import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+import java.util.Map;
+
+public class RoutingDataSource extends AbstractRoutingDataSource {
+
+    public static RoutingDataSource createDefaultSetting(final Map<Object, Object> dataSources) {
+        final RoutingDataSource routingDataSource = new RoutingDataSource();
+        routingDataSource.setDefaultTargetDataSource(dataSources.get(DataSourceType.SOURCE));
+        routingDataSource.setTargetDataSources(dataSources);
+        return routingDataSource;
+    }
+
+    @Override
+    protected Object determineCurrentLookupKey() {
+        final boolean readOnly = TransactionSynchronizationManager.isCurrentTransactionReadOnly();
+
+        if (readOnly) {
+            return DataSourceType.REPLICA;
+        }
+
+        return DataSourceType.SOURCE;
+    }
+}