apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/InstanceService.java/InstanceService/getByNamespace
class InstanceService:  public PageDTO<InstanceDTO> getByNamespace(Env env, String appId, String clusterName, String namespaceName,
                                             String instanceAppId, int page, int size){
    return instanceAPI.getByNamespace(appId, env, clusterName, namespaceName, instanceAppId, page, size);
  }