code: protected DataSource createDataSourceInstance(String identifier) throws Exception {
  		DBInstance instance = getDbInstance(identifier);
  		return this.dataSourceFactory.createDataSource(fromRdsInstance(instance));
  	}
docs: Creates a data source based in the instance name. The physical information for the
  data source is retrieved by the name passed as identifier. This method does
  distinguish between regular amazon rds instances and read-replicas because both
  meta-data is retrieved on the same way.
  @param identifier - the database identifier for the data source configured in
  amazon rds
  @return a fully configured and initialized {@link javax.sql.DataSource}
  @throws java.lang.IllegalStateException if no database has been found
  @throws java.lang.Exception in case of underlying exceptions