apollo-adminservice/src/main/java/com/ctrip/framework/apollo/adminservice/controller/ClusterController.java/ClusterController/delete
class ClusterController:  @DeleteMapping("/apps/{appId}/clusters/{clusterName:.+}")
  public void delete(@PathVariable("appId") String appId,
                     @PathVariable("clusterName") String clusterName, @RequestParam String operator) {

    Cluster entity = clusterService.findOne(appId, clusterName);

    if (entity == null) {
      throw new NotFoundException("cluster not found for clusterName " + clusterName);
    }

    if(ConfigConsts.CLUSTER_NAME_DEFAULT.equals(entity.getName())){
      throw new BadRequestException("can not delete default cluster!");
    }

    clusterService.delete(entity.getId(), operator);
  }