It is built around the [Kubernetes Ingress resource](https://kubernetes.io/docs/concepts/services-networking/ingress/), using a [ConfigMap](https://kubernetes.io/docs/concepts/configuration/configmap/) to store the controller configuration.
You can learn more about using [Ingress](http://kubernetes.io/docs/user-guide/ingress/) in the official [Kubernetes documentation](https://docs.k8s.io).
If you are using Ingress objects in your cluster (running Kubernetes older than v1.22), and you plan to upgrade to Kubernetes v1.22, this section is relevant to you.
IngressClass is a Kubernetes resource. See the description below. It's important because until now, a default install of the Ingress-NGINX controller did not require any IngressClass object. From version 1.0.0 of the Ingress-NGINX Controller, an IngressClass object is required.
On clusters with more than one instance of the Ingress-NGINX controller, all instances of the controllers must be aware of which Ingress objects they serve. The `ingressClassName` field of an Ingress is the way to let the controller know about that.
From K8s version 1.22 onwards, you can **only** access the Ingress API via the stable, `networking.k8s.io/v1` API. The reason is explained in the [official blog on deprecated ingress API versions](https://kubernetes.io/blog/2021/07/26/update-with-ingress-nginx/).
If you are already using the Ingress-NGINX controller and then upgrade to K8s version v1.22 , there are several scenarios where your existing Ingress objects will not work how you expect. Read this FAQ to check which scenario matches your use case.
If a single instance of the Ingress-NGINX controller is the sole Ingress controller running in your cluster, you should add the annotation "ingressclass.kubernetes.io/is-default-class" in your IngressClass, so any new Ingress objects will have this one as default IngressClass.
When using Helm, you can enable this annotation by setting `.controller.ingressClassResource.default: true` in your Helm chart installation's values file.
If you have any old Ingress objects remaining without an IngressClass set, you can do one or more of the following to make the Ingress-NGINX controller aware of the old objects:
- You can manually set the [`.spec.ingressClassName`](https://kubernetes.io/docs/reference/kubernetes-api/service-resources/ingress-v1/#IngressSpec) field in the manifest of your own Ingress resources.
- You can re-create them after setting the `ingressclass.kubernetes.io/is-default-class` annotation to `true` on the IngressClass
- Alternatively you can make the Ingress-NGINX controller watch Ingress objects without the ingressClassName field set by starting your Ingress-NGINX with the flag [--watch-ingress-without-class=true](#what-is-the-flag-watch-ingress-without-class) . When using Helm, you can configure your Helm chart installation's values file with `.controller.watchIngressWithoutClass: true`
## I have multiple ingress objects in my cluster. What should I do ?
- If you have lot of ingress objects without ingressClass configuration, you can run the ingress-controller with the flag `--watch-ingress-without-class=true`.
Even though `kubernetes.io/ingress.class` is deprecated, the Ingress-NGINX controller still understands that annotation.
If you want to follow good practice, you should consider migrating to use IngressClass and `.spec.ingressClassName`.
## I have more than one controller running in my cluster, and I want to use the new API ?
In this scenario, you need to create multiple IngressClasses (see example one). But be aware that IngressClass works in a very specific way: you will need to change the `.spec.controller` value in your IngressClass and configure the controller to expect the exact same value.
- Ingress-Nginx A, configured to use controller class name `example.com/ingress-nginx1`
- Ingress-Nginx B, configured to use controller class name `example.com/ingress-nginx2`
Then, when you create an Ingress object with its `ingressClassName` set to `ingress-nginx-two`, only controllers looking for the `example.com/ingress-nginx2` controller class pay attention to the new object. Given that Ingress-Nginx B is set up that way, it will serve that object, whereas Ingress-Nginx A ignores the new Ingress.
If you start Ingress-Nginx B with the command line argument `--watch-ingress-without-class=true` and you run Ingress-Nginx A with the command line argument `--watch-ingress-without-class=false` then this is a supported configuration. If you have two Ingress-NGINX controllers for the same cluster, both running with `--watch-ingress-without-class=true` then there is likely to be a conflict.
## I am seeing this error message in the logs of the Ingress-NGINX controller: "ingress class annotation is not equal to the expected by Ingress Controller". Why ?
- It is highly likely that you will also see the name of the ingress resource in the same error message. This error message has been observed on use the deprecated annotation (`kubernetes.io/ingress.class`) in a Ingress resource manifest. It is recommended to use the `.spec.ingressClassName` field of the Ingress resource, to specify the name of the IngressClass of the Ingress you are defining.
- Use Helm to install the additional instance of the ingress controller
- Ensure you have Helm working (refer to the [Helm documentation](https://helm.sh/docs/))
- We have to assume that you have the helm repo for the ingress-NGINX controller already added to your Helm config. But, if you have not added the helm repo then you can do this to add the repo to your helm config;
- If you need to install yet another instance, then repeat the procedure to create a new namespace, change the values such as names & namespaces (for example from "-2" to "-3"), or anything else that meets your needs.
