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Using Gateway API

Gateway API is a set of resources for configuring networking in Kubernetes. It expands on Ingress to configure additional types of routes (TCP, UDP, and TLS in addition to HTTP/HTTPS), support backends other than Service, and manage the proxies that implement routes.

Gateway API and Kong’s implementation of Gateway API are both in alpha stage and under active development. Features and implementation specifics will change before their initial general availability release.

Supported Gateway API Resources

Currently, the Kong Ingress Controller’s implementation of the Gateway API supports the following resources:

Enable the feature

The Gateway API CRDs are not yet available by default in Kubernetes. You must first install them.

The default controller configuration enables Gateway API handling, however the alpha features of Gateway API are still behind a feature flag in Kong Ingress Controller. To enable it, set ingressController.env.feature_gates: GatewayAlpha=true in your Helm values.yaml, or set CONTROLLER_FEATURE_GATES=GatewayAlpha=true if not using Helm.

Note that you must restart Pods with this flag set after installing the Gateway API CRDs.

If using Helm, you must use chart version 2.7 or higher. Older versions do not include the ServiceAccount permissions necessary for KIC to read Gateway API resources.

Testing connectivity to Kong

This guide assumes that the PROXY_IP environment variable is set to contain the IP address or URL pointing to Kong. Follow one of the deployment guides to configure this environment variable.

If everything is set up correctly, making a request to Kong should return HTTP 404 Not Found.

Note: If you are running the example using Minikube on MacOS, you may need to run minikube tunnel in a separate terminal window. This exposes LoadBalancer services externally, which is not enabled by default.

$ curl -i $PROXY_IP
HTTP/1.1 404 Not Found
Content-Type: application/json; charset=utf-8
Connection: keep-alive
Content-Length: 48
Server: kong/1.2.1

{"message":"no Route matched with those values"}

This is expected, as Kong does not yet know how to proxy the request.

Set up an echo service

Set up an echo service to demonstrate how to use the Kong Ingress Controller:

kubectl apply -f https://docs.jp.konghq.com/assets/kubernetes-ingress-controller/examples/echo-service.yaml

Add a GatewayClass and Gateway

The Gateway resource represents the proxy instance that handles traffic for a set of Gateway API routes, and a GatewayClass describes characteristics shared by all Gateways of a given type.

Add a GatewayClass:

$ echo "apiVersion: gateway.networking.k8s.io/v1beta1
kind: GatewayClass
metadata:
  name: kong
  annotations:
    konghq.com/gatewayclass-unmanaged: 'true'
spec:
  controllerName: konghq.com/kic-gateway-controller
" | kubectl apply -f -

gatewayclass.gateway.networking.k8s.io/kong created

Add a Gateway:

$ echo "apiVersion: gateway.networking.k8s.io/v1beta1
kind: Gateway
metadata:
  name: kong
spec:
  gatewayClassName: kong
  listeners:
  - name: proxy
    port: 80
    hostname: kong.example
    protocol: HTTP
" | kubectl apply -f -

gateway.gateway.networking.k8s.io/kong created

This configuration does create an HTTPS listen, as this requires a certificate. If you have a TLS Secret you wish to use, you can add an HTTPS listen with:

kubectl patch --type=json gateway kong -p='[{
    "op":"add",
	"path":"/spec/listeners/-",
	"value":{
		"name":"proxy-ssl",
		"hostname":"kong.example",
		"port":443,
		"protocol":"HTTPS",
		"tls":{
				"certificateRefs":[{
				    "group":"",
					"kind":"Secret",
					"name":"example-cert-secret"
				}]
		}
    }
}]'

Change example-cert-secret to the name of your Secret.

To configure KIC to reconcile the Gateway resource, you must set the konghq.com/gatewayclass-unmanaged annotation as the example in GatewayClass resource used in spec.gatewayClassName in Gateway resource. Also, the spec.controllerName of GatewayClass needs to be same as the value of the --gateway-api-controller-name flag configured in KIC. For more information, see kic-flags.

You can check to confirm if KIC has updated the bound Gateway by inspecting the list of associated addresses:

kubectl get gateway kong -o=jsonpath='{.status.addresses}' | jq

[
  {
    "type": "IPAddress",
    "value": "10.96.179.122"
  },
  {
    "type": "IPAddress",
    "value": "172.18.0.240"
  }
]

Add an HTTPRoute

HTTPRoute resources are similar to Ingress resources: they contain a set of matching criteria for HTTP requests and upstream Services to route those requests to.

The Gateway API specification binds HTTPRoutes to one or more listeners in a Gateway resource. These listeners have a specific port, and HTTPRoutes should only be available on their listeners’ ports per the specification. Kong’s HTTP proxy implementation doesn’t support this. If you configure multiple HTTP ports, Kong serves all HTTP routes on all ports.

$ echo "apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: echo
  annotations:
    konghq.com/strip-path: 'true'
spec:
  parentRefs:
  - group: gateway.networking.k8s.io
    kind: Gateway
    name: kong
  hostnames:
  - kong.example
  rules:
  - backendRefs:
    - group: ""
      kind: Service
      name: echo
      port: 80
      weight: 1
    matches:
    - path:
        type: PathPrefix
        value: /echo
" | kubectl apply -f -

After creating an HTTPRoute, accessing /echo/hostname forwards a request to the echo service’s /hostname path, which yields the name of the pod that served the request:

curl -i http://kong.example/echo/hostname --resolve kong.example:80:$PROXY_IP

HTTP/1.1 200 OK
Content-Type: text/plain; charset=utf-8
Content-Length: 21
Connection: keep-alive
Date: Fri, 28 Oct 2022 08:18:18 GMT
X-Kong-Upstream-Latency: 1
X-Kong-Proxy-Latency: 0
Via: kong/3.1.1

echo-658c5ff5ff-8cvgj%

Traffic splitting with HTTPRoute

HTTPRoute contains a BackendRefs field, which allows users to specify weight parameters for echo BackendRef. This can be used to perform traffic splitting.

To do so, you can deploy a second echo Service so that you have a second BackendRef to use for traffic splitting.

kubectl apply -f https://docs.jp.konghq.com/assets/kubernetes-ingress-controller/examples/echo-services.yaml

Note: This example contains the previous echo Service so you may deploy it without deploying the previous example from the Set up an echo service section.

Now that those two Services are deployed, you can now deploy your HTTPRoute. This will perform the traffic splitting between them using the weight parameters:

echo 'apiVersion: gateway.networking.k8s.io/v1beta1
kind: HTTPRoute
metadata:
  name: echo
  annotations:
    konghq.com/strip-path: "true"
spec:
  parentRefs:
  - name: kong
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /echo
    backendRefs:
    - name: echo
      kind: Service
      port: 80
      weight: 75
    - name: echo2
      kind: Service
      port: 80
      weight: 25
' | kubectl apply -f -

Now, accessing /echo/hostname should distribute around 75% of requests to Service echo and around 25% of requests to Service echo2.

curl http://kong.example/echo/hostname --resolve kong.example:80:$PROXY_IP
echo2-7cb798f47-gh4xg%
curl http://kong.example/echo/hostname --resolve kong.example:80:$PROXY_IP
echo-658c5ff5ff-8cvgj%
curl http://kong.example/echo/hostname --resolve kong.example:80:$PROXY_IP
echo-658c5ff5ff-8cvgj%
curl http://kong.example/echo/hostname --resolve kong.example:80:$PROXY_IP
echo-658c5ff5ff-8cvgj%

Beta limitations

Kong Ingress Controller Gateway API support is a work in progress, and not all features of Gateway APIs are supported. In particular:

queryParam matches are not supported.
Gateways are not provisioned automatically.
Kong only supports a single Gateway per GatewayClass.
HTTPRoutes cannot be bound to a specific port using a ParentReference. Kong serves all HTTP routes on all HTTP listeners.