@Override
    public ClusterMasterDTO getMaster() {
        ClusterMasterDO masterDO = clusterMasterMapper.selectById(MASTER_ID);
        return Objects.isNull(masterDO) ? new ClusterMasterDTO() : ClusterMasterTransfer.INSTANCE.mapToDTO(masterDO);
    }
The cluster select master service jdbc impl.
shenyu-admin/src/main/java/org/apache/shenyu/admin/mode/cluster/impl/jdbc/ClusterSelectMasterServiceJdbcImpl.java