apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/NamespaceBranchService.java/NamespaceBranchService/createBranch
class NamespaceBranchService:  @Transactional
  public NamespaceDTO createBranch(String appId, Env env, String parentClusterName, String namespaceName) {
    String operator = userInfoHolder.getUser().getUserId();
    return createBranch(appId, env, parentClusterName, namespaceName, operator);
  }