ingress-nginx-helm/docs/user-guide/multiple-ingress.md

Multiple Ingress controllers

If you're running multiple ingress controllers, or running on a cloud provider that natively handles ingress such as GKE, you need to specify the annotation kubernetes.io/ingress.class: "nginx" in all ingresses that you would like the ingress-nginx controller to claim.

For instance,

metadata:
  name: foo
  annotations:
    kubernetes.io/ingress.class: "gce"

will target the GCE controller, forcing the nginx controller to ignore it, while an annotation like

metadata:
  name: foo
  annotations:
    kubernetes.io/ingress.class: "nginx"

will target the nginx controller, forcing the GCE controller to ignore it.

To reiterate, setting the annotation to any value which does not match a valid ingress class will force the NGINX Ingress controller to ignore your Ingress. If you are only running a single NGINX ingress controller, this can be achieved by setting the annotation to any value except "nginx" or an empty string.

Do this if you wish to use one of the other Ingress controllers at the same time as the NGINX controller.

Multiple ingress-nginx controllers

This mechanism also provides users the ability to run multiple NGINX ingress controllers (e.g. one which serves public traffic, one which serves "internal" traffic). To do this, the option --ingress-class must be changed to a value unique for the cluster within the definition of the replication controller. Here is a partial example:

spec:
  template:
     spec:
       containers:
         - name: nginx-ingress-internal-controller
           args:
             - /nginx-ingress-controller
             - '--ingress-class=nginx-internal'
             - '--configmap=ingress/nginx-ingress-internal-controller'

!!! important Deploying multiple Ingress controllers, of different types (e.g., ingress-nginx & gce), and not specifying a class annotation will result in both or all controllers fighting to satisfy the Ingress, and all of them racing to update Ingress status field in confusing ways.

When running multiple ingress-nginx controllers, it will only process an unset class annotation if one of the controllers uses the default
`--ingress-class` value (see `IsValid` method in `internal/ingress/annotations/class/main.go`), otherwise the class annotation become required.

If `--ingress-class` is set to the default value of `nginx`, the controller will monitor Ingresses with no class annotation *and* Ingresses with annotation class set to `nginx`. Use a non-default value for `--ingress-class`, to ensure that the controller only satisfied the specific class of Ingresses.