Add description on how to configure each ingress for knative serving (#3025)

* Add description on how to configure each ingress for knative serving

* Rephrase the sentence in a correct order

Author: Vincent

docs/install/knative-with-operators.md

@@ -207,6 +207,358 @@ NAME              VERSION             READY   REASON
 knative-serving   <version number>    True
 ```
 
+### Installing the Knative Serving component with different network layers
+
+Knative Operator can configure Knative Serving component with different network layer options. Istio is the default network
+layer, if the ingress is not specified in the Knative Serving CR. Click on each tab below to see how you can configure
+Knative Serving with different ingresses:
+
+   {{< tabs name="serving_networking" default="Ambassador" >}}
+   {{% tab name="Ambassador" %}}
+
+{{% feature-state version="v0.8" state="alpha" %}}
+
+The following commands install Ambassador and enable its Knative integration.
+
+1. Create a namespace to install Ambassador in:
+
+   ```bash
+   kubectl create namespace ambassador
+   ```
+
+1. Install Ambassador:
+
+   ```bash
+   kubectl apply --namespace ambassador \
+     --filename https://getambassador.io/yaml/ambassador/ambassador-crds.yaml \
+     --filename https://getambassador.io/yaml/ambassador/ambassador-rbac.yaml \
+     --filename https://getambassador.io/yaml/ambassador/ambassador-service.yaml
+   ```
+
+1. Give Ambassador the required permissions:
+
+   ```bash
+   kubectl patch clusterrolebinding ambassador -p '{"subjects":[{"kind": "ServiceAccount", "name": "ambassador", "namespace": "ambassador"}]}'
+   ```
+
+1. Enable Knative support in Ambassador:
+
+   ```bash
+   kubectl set env --namespace ambassador  deployments/ambassador AMBASSADOR_KNATIVE_SUPPORT=true
+   ```
+
+1. To configure Knative Serving to use Ambassador, apply the content of the Serving CR as below:
+
+   ```bash
+   cat <<-EOF | kubectl apply -f -
+   apiVersion: operator.knative.dev/v1alpha1
+   kind: KnativeServing
+   metadata:
+     name: knative-serving
+     namespace: knative-serving
+   spec:
+     config:
+       network:
+         ingress.class: "ambassador.ingress.networking.knative.dev"
+   EOF
+   ```
+
+1. Fetch the External IP or CNAME:
+
+   ```bash
+   kubectl --namespace ambassador get service ambassador
+   ```
+
+   Save this for configuring DNS below.
+
+{{< /tab >}}
+
+{{% tab name="Contour" %}}
+
+{{% feature-state version="v0.18" state="stable" %}}
+
+The following commands install Contour and enable its Knative integration.
+
+1. Install a properly configured Contour:
+
+   ```bash
+   kubectl apply --filename {{< artifact repo="net-contour" file="contour.yaml" >}}
+   ```
+
+1. Install the Knative Contour controller:
+
+   ```bash
+   kubectl apply --filename {{< artifact repo="net-contour" file="net-contour.yaml" >}}
+   ```
+
+1. To configure Knative Serving to use Contour, apply the content of the Serving CR as below:
+
+   ```bash
+   cat <<-EOF | kubectl apply -f -
+   apiVersion: operator.knative.dev/v1alpha1
+   kind: KnativeServing
+   metadata:
+     name: knative-serving
+     namespace: knative-serving
+   spec:
+     config:
+       network:
+         ingress.class: "contour.ingress.networking.knative.dev"
+   EOF
+   ```
+
+1. Fetch the External IP or CNAME:
+
+   ```bash
+   kubectl --namespace contour-external get service envoy
+   ```
+
+   Save this for configuring DNS below.
+
+{{< /tab >}}
+
+{{% tab name="Gloo" %}}
+
+{{% feature-state version="v0.8" state="alpha" %}}
+
+_For a detailed guide on Gloo integration, see
+[Installing Gloo for Knative](https://docs.solo.io/gloo/latest/installation/knative/)
+in the Gloo documentation._
+
+The following commands install Gloo and enable its Knative integration.
+
+1. Make sure `glooctl` is installed (version 1.3.x and higher recommended):
+
+   ```bash
+   glooctl version
+   ```
+
+   If it is not installed, you can install the latest version using:
+
+   ```bash
+   curl -sL https://run.solo.io/gloo/install | sh
+   export PATH=$HOME/.gloo/bin:$PATH
+   ```
+
+   Or following the
+   [Gloo CLI install instructions](https://docs.solo.io/gloo/latest/installation/knative/#install-command-line-tool-cli).
+
+1. Install Gloo and the Knative integration:
+
+   ```bash
+   glooctl install knative --install-knative=false
+   ```
+
+1. To configure Knative Serving to use Gloo, apply the content of the Serving CR as below:
+
+   ```bash
+   cat <<-EOF | kubectl apply -f -
+   apiVersion: operator.knative.dev/v1alpha1
+   kind: KnativeServing
+   metadata:
+     name: knative-serving
+     namespace: knative-serving
+   spec:
+     ingress:
+       gloo:
+         enabled: true
+   EOF
+   ```
+
+1. Fetch the External IP or CNAME:
+
+   ```bash
+   glooctl proxy url --name knative-external-proxy
+   ```
+
+   Save this for configuring DNS below.
+
+{{< /tab >}}
+
+{{% tab name="Kong" %}}
+
+{{% feature-state version="v0.13" state="" %}}
+
+The following commands install Kong and enable its Knative integration.
+
+1. Install Kong Ingress Controller:
+
+   ```bash
+   kubectl apply --filename https://raw.githubusercontent.com/Kong/kubernetes-ingress-controller/0.9.x/deploy/single/all-in-one-dbless.yaml
+   ```
+
+1. To configure Knative Serving to use Kong, apply the content of the Serving CR as below:
+
+   ```bash
+   cat <<-EOF | kubectl apply -f -
+   apiVersion: operator.knative.dev/v1alpha1
+   kind: KnativeServing
+   metadata:
+     name: knative-serving
+     namespace: knative-serving
+   spec:
+     config:
+       network:
+         ingress.class: "kong"
+   EOF
+   ```
+
+1. Fetch the External IP or CNAME:
+
+   ```bash
+   kubectl --namespace kong get service kong-proxy
+   ```
+
+   Save this for configuring DNS below.
+
+{{< /tab >}}
+
+{{% tab name="Kourier" %}}
+
+{{% feature-state version="v0.17" state="beta" %}}
+
+The following commands install Kourier and enable its Knative integration.
+
+1. Install the Knative Kourier controller:
+
+   ```bash
+   kubectl apply --filename {{< artifact repo="net-kourier" file="kourier.yaml" >}}
+   ```
+
+1. To configure Knative Serving to use Kourier, apply the content of the Serving CR as below:
+
+   ```bash
+   cat <<-EOF | kubectl apply -f -
+   apiVersion: operator.knative.dev/v1alpha1
+   kind: KnativeServing
+   metadata:
+     name: knative-serving
+     namespace: knative-serving
+   spec:
+     config:
+       network:
+         ingress.class: "kourier.ingress.networking.knative.dev"
+   EOF
+   ```
+
+1. Fetch the External IP or CNAME:
+
+   ```bash
+   kubectl --namespace knative-serving get service kourier
+   ```
+
+   Save this for configuring DNS below.
+
+{{< /tab >}} {{< /tabs >}}
+
+1. Configure DNS
+
+      <!-- This indentation is important for things to render properly. -->
+
+   {{< tabs name="serving_dns" >}} {{% tab name="Magic DNS (xip.io)" %}} We ship
+   a simple Kubernetes Job called "default domain" that will (see caveats)
+   configure Knative Serving to use <a href="http://xip.io">xip.io</a> as the
+   default DNS suffix.
+
+```bash
+kubectl apply --filename {{< artifact repo="serving" file="serving-default-domain.yaml" >}}
+```
+
+**Caveat**: This will only work if the cluster LoadBalancer service exposes an
+IPv4 address or hostname, so it will not work with IPv6 clusters or local setups
+like Minikube. For these, see "Real DNS" or "Temporary DNS". {{< /tab >}}
+
+{{% tab name="Real DNS" %}} To configure DNS for Knative, take the External IP
+or CNAME from setting up networking, and configure it with your DNS provider as
+follows:
+
+- If the networking layer produced an External IP address, then configure a
+  wildcard `A` record for the domain:
+
+  ```
+  # Here knative.example.com is the domain suffix for your cluster
+  *.knative.example.com == A 35.233.41.212
+  ```
+
+- If the networking layer produced a CNAME, then configure a CNAME record for
+  the domain:
+
+  ```
+  # Here knative.example.com is the domain suffix for your cluster
+  *.knative.example.com == CNAME a317a278525d111e89f272a164fd35fb-1510370581.eu-central-1.elb.amazonaws.com
+  ```
+
+Once your DNS provider has been configured, add the following section into your existing Serving CR, and apply it:
+
+```bash
+# Replace knative.example.com with your domain suffix
+apiVersion: operator.knative.dev/v1alpha1
+kind: KnativeServing
+metadata:
+  name: knative-serving
+  namespace: knative-serving
+spec:
+  config:
+    domain:
+      "knative.example.com": ""
+  ...
+```
+
+{{< /tab >}}
+
+{{% tab name="Temporary DNS" %}} If you are using `curl` to access the sample
+applications, or your own Knative app, and are unable to use the "Magic DNS
+(xip.io)" or "Real DNS" methods, there is a temporary approach. This is useful
+for those who wish to evaluate Knative without altering their DNS configuration,
+as per the "Real DNS" method, or cannot use the "Magic DNS" method due to using,
+for example, minikube locally or IPv6 clusters.
+
+To access your application using `curl` using this method:
+
+1. After starting your application, get the URL of your application:
+
+   ```bash
+   kubectl get ksvc
+   ```
+
+   The output should be similar to:
+
+   ```bash
+   NAME            URL                                        LATESTCREATED         LATESTREADY           READY   REASON
+   helloworld-go   http://helloworld-go.default.example.com   helloworld-go-vqjlf   helloworld-go-vqjlf   True
+   ```
+
+1. Instruct `curl` to connect to the External IP or CNAME defined by the
+   networking layer in section 3 above, and use the `-H "Host:"` command-line
+   option to specify the Knative application's host name. For example, if the
+   networking layer defines your External IP and port to be
+   `http://192.168.39.228:32198` and you wish to access the above
+   `helloworld-go` application, use:
+
+   ```bash
+   curl -H "Host: helloworld-go.default.example.com" http://192.168.39.228:32198
+   ```
+
+   In the case of the provided `helloworld-go` sample application, using the default
+   configuration, the output should be:
+
+   ```
+   Hello Go Sample v1!
+   ```
+
+Refer to the "Real DNS" method for a permanent solution.
+
+{{< /tab >}}
+
+{{< /tabs >}}
+
+1. Monitor the Knative components until all of the components show a `STATUS` of
+   `Running` or `Completed`:
+
+   ```bash
+   kubectl get pods --namespace knative-serving
+   ```
+
 ### Installing the Knative Eventing component
 
 1. Create and apply the Knative Eventing CR: