apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/NamespaceBranchService.java/NamespaceBranchService/createChildCluster
class NamespaceBranchService:  private Cluster createChildCluster(String appId, Cluster parentCluster,
                                     String namespaceName, String operator) {

    Cluster childCluster = new Cluster();
    childCluster.setAppId(appId);
    childCluster.setParentClusterId(parentCluster.getId());
    childCluster.setName(UniqueKeyGenerator.generate(appId, parentCluster.getName(), namespaceName));
    childCluster.setDataChangeCreatedBy(operator);
    childCluster.setDataChangeLastModifiedBy(operator);

    return childCluster;
  }