kubernetes之ingress error: endpoints "default-http-backend" not found

[root@k8s-master k8s-yaml]# kubectl describe ing
Name: my-ingress-for-nginx
Namespace: default
Address:
Default backend: default-http-backend:80 (<error: endpoints "default-http-backend" not found>)
Rules:
Host Path Backends
---- ---- --------
a.demo.kuboard.cn
/ my-service:80 (10.244.0.30:80,10.244.2.15:80)
Annotations: Events: <none>

为什么会找不到:官网给出的解释: Note: Depending on the Ingress controller you are using, you may need to create a default-http-backend Service.
Default Backend
An Ingress with no rules sends all traffic to a single default backend. The default backend is typically a configuration option of the Ingress controller and is not specified in your Ingress resources.
If none of the hosts or paths match the HTTP request in the Ingress objects, the traffic is routed to your default backend.

翻译：
控制器。注意:根据您正在使用的Ingress控制器，您可能需要创建一个default-http-backend服务。
违约后端
没有规则的入口将所有流量发送到一个默认后端。默认后端通常是Ingress控制器的一个配置选项，在您的Ingress资源中没有指定。
如果Ingress对象中的主机或路径都不匹配HTTP请求，则流量将被路由到默认后端。