Document VirtualServer routeSelector no-match warning (NIC)

content/nic/configuration/virtualserver-and-virtualserverroute-resources.md

@@ -231,6 +231,8 @@ See the [VirtualServerRoute specification](#virtualserverroute-specification) se
 |``matchLabels`` | A map of key-value pairs. Each key-value pair in the matchLabels map is equivalent to an element of matchExpressions, whose key field is "key", the operator is "In", and the values array contains only "value". The requirements are ANDed. | ``map[string]string`` | Yes |
 |``matchExpressions`` | A list of label selector requirements. The requirements are ANDed. For more information on label selector requirements, see the [Kubernetes documentation](https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#resources-that-support-set-based-requirements). | N/A | No |
 
+{{< call-out class="note" >}} If a `routeSelector` matches no VirtualServerRoutes, the VirtualServer reports `State: Warning` and NGINX Ingress Controller emits a `Warning` event. For details, see [Warning events]({{< ref "/nic/troubleshooting/troubleshoot-virtualserver.md#warning-events" >}}). {{< /call-out >}}
+
 ## VirtualServerRoute specification
 
 The VirtualServerRoute resource defines a route for a VirtualServer. It can consist of one or multiple subroutes. The VirtualServerRoute is an alternative to [Mergeable Ingress types]({{< ref "/nic/configuration/ingress-resources/cross-namespace-configuration.md" >}}).

content/nic/troubleshooting/troubleshoot-virtualserver.md

@@ -36,3 +36,34 @@ Events:
   ----     ------                 ----  ----                      -------
   Normal   AddedOrUpdated         1m    nginx-ingress-controller  Configuration for default/coffee was added or updated
 ```
+
+### Warning events
+
+When a VirtualServer's `routeSelector` matches no VirtualServerRoutes, F5 NGINX Ingress Controller emits a `Warning` event, and the VirtualServer reports `State: Warning`. The warning shows that the VirtualServer serves no routes for the selected paths. Use this event to find a VirtualServer whose selector no longer matches any VirtualServerRoutes.
+
+A `routeSelector` matches no VirtualServerRoutes in these cases:
+
+- The selected VirtualServerRoutes are deleted.
+- Their `ingressClassName` changes, so NGINX Ingress Controller no longer owns them.
+- Their labels change, so they no longer match the selector.
+
+To see this event, describe the VirtualServer:
+
+```shell
+kubectl describe vs cafe
+```
+
+```shell
+Events:
+  Type     Reason                     Age   From                      Message
+  ----     ------                     ----  ----                      -------
+  Warning  AddedOrUpdatedWithWarning  16s   nginx-ingress-controller  Configuration for default/cafe was added or updated with warning(s): VirtualServerRoute routeSelector app=coffee matched no VirtualServerRoutes
+```
+
+To clear the warning, make sure at least one VirtualServerRoute matches the selector:
+
+- Recreate a deleted VirtualServerRoute.
+- Restore its `ingressClassName`.
+- Reapply the labels the selector requires.
+
+After you apply one of these fixes, `kubectl describe vs cafe` shows the `Normal` `AddedOrUpdated` event again. `State` returns to `Valid`.