// If requested to pre-populate database from a backup of previous/existing database
// and updates clusterState with DB credentials
func (bkr *Broker) prepopulateDatabaseFromExistingClusterData(existingClusterData *structs.ClusterRecreationData, toInstanceID structs.ClusterID, clusterModel *state.ClusterModel, logger lager.Logger) (err error) {
	if bkr.backups.BaseURI == "" {
		return fmt.Errorf("Failed to copy existing database backup: missing backups.base_uri configuration")
	}
	fromDatabaseBackup := fmt.Sprintf("%s/%s", bkr.backups.BaseURI, existingClusterData.InstanceID)
	toDatabaseBackup := fmt.Sprintf("%s/%s", bkr.backups.BaseURI, toInstanceID)
	err = bkr.callbacks.CopyDatabaseBackup(fromDatabaseBackup, toDatabaseBackup, bkr.logger)
	if err != nil {
		logger.Error("prepopulate-database", err)
		return fmt.Errorf("Failed to copy existing database backup to new database: %s", err.Error())
	}

	return clusterModel.UpdateCredentials(existingClusterData)
}