Configuring the ingress gateway¶

Knative uses a shared ingress Gateway to serve all incoming traffic within Knative service mesh, which is the knative-ingress-gateway Gateway under the knative-serving namespace. By default, we use Istio gateway service istio-ingressgateway under istio-system namespace as its underlying service. You can replace the service and the gateway with that of your own as follows.

Replace the default `istio-ingressgateway` service¶

Step 1: Create the gateway service and deployment instance¶

You'll need to create the gateway service and deployment instance to handle traffic first. Let's say you customized the default istio-ingressgateway to custom-ingressgateway as follows.

apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
spec:
  components:
    ingressGateways:
      - name: custom-ingressgateway
        enabled: true
        namespace: custom-ns
        label:
          istio: custom-gateway

Step 2: Update the Knative gateway¶

Update gateway instance knative-ingress-gateway under knative-serving namespace:

kubectl edit gateway knative-ingress-gateway -n knative-serving

Replace the label selector with the label of your service:

istio: ingressgateway

For the example custom-ingressgateway service mentioned earlier, it should be updated to:

istio: custom-gateway

If there is a change in service ports (compared with that of istio-ingressgateway), update the port info in the gateway accordingly.

Step 3: Update the gateway ConfigMap¶

Update gateway configmap config-istio under knative-serving namespace:

kubectl edit configmap config-istio -n knative-serving

This command opens your default text editor and allows you to edit the config-istio ConfigMap.

apiVersion: v1
data:
  _example: |
    ################################
    #                              #
    #    EXAMPLE CONFIGURATION     #
    #                              #
    ################################
    # ...
    external-gateways: |
      - name: knative-ingress-gateway
        namespace: knative-serving
        service: istio-ingressgateway.istio-system.svc.cluster.local

Edit the file to add the external-gateways field with the fully qualified url of your service. For the example custom-ingressgateway service mentioned earlier, it should be updated to:

apiVersion: v1
data:
  external-gateways: |
    - name: knative-ingress-gateway
      namespace: knative-serving
      service: custom-ingressgateway.custom-ns.svc.cluster.local
kind: ConfigMap
[...]

Replace the `knative-ingress-gateway` gateway¶

We customized the gateway service so far, but we may also want to use our own gateway. We can replace the default gateway with our own gateway with following steps.

Step 1: Create the gateway¶

Let's say you replace the default knative-ingress-gateway gateway with knative-custom-gateway in custom-ns. First, create the knative-custom-gateway gateway:

Create a YAML file using the following template:

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: knative-custom-gateway
  namespace: custom-ns
spec:
  selector:
    istio: <service-label>
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - "*"

Where <service-label> is a label to select your service, for example, ingressgateway.

Apply the YAML file by running the command:
```
kubectl apply -f <filename>.yaml
```
Where <filename> is the name of the file you created in the previous step.

Step 2: Update the gateway ConfigMap¶

Update gateway configmap config-istio under knative-serving namespace:

kubectl edit configmap config-istio -n knative-serving

This command opens your default text editor and allows you to edit the config-istio ConfigMap.

apiVersion: v1
data:
  _example: |
    ################################
    #                              #
    #    EXAMPLE CONFIGURATION     #
    #                              #
    ################################
    # ...
    external-gateways: |
      - name: knative-ingress-gateway
        namespace: knative-serving
        service: istio-ingressgateway.istio-system.svc.cluster.local

Edit the file to add the external-gateways field with the customized gateway. For the example knative-custom-gateway mentioned earlier, it should be updated to:

apiVersion: v1
data:
  external-gateways: |
    - name: knative-custom-gateway
      namespace: custom-ns
      service: istio-ingressgateway.istio-system.svc.cluster.local
kind: ConfigMap
[...]

The configuration format should be

  external-gateways: |
    - name: <gateway-name>
      namespace: <gateway-namespace>
      service: <fully-qualified-url-of-istio-ingress-service>