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Using annotated Gateway API Gateway and/or HTTPRoutes as Source

This tutorial describes how to use annotated Gateway API resources as source for DNSEntries with the Gardener shoot-dns-service extension.

The dns-controller-manager supports the resources Gateway and HTTPRoute.

Install Istio on your cluster

Using a new or existing shoot cluster, follow the Istio Kubernetes Gateway API to install the Gateway API and to install Istio.

These are the typical commands for the Istio installation with the Kubernetes Gateway API:

export KUEBCONFIG=...
curl -L https://istio.io/downloadIstio | sh -
kubectl get crd gateways.gateway.networking.k8s.io &> /dev/null || \
  { kubectl kustomize "github.com/kubernetes-sigs/gateway-api/config/crd?ref=v1.0.0" | kubectl apply -f -; }
istioctl install --set profile=minimal -y
kubectl label namespace default istio-injection=enabled

Verify that Gateway Source works

Install a sample service

With automatic sidecar injection:

$ kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.20/samples/httpbin/httpbin.yaml

Using a Gateway as a source

Deploy the Gateway API configuration including a single exposed route (i.e., /get):

kubectl create namespace istio-ingress
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: gateway
  namespace: istio-ingress
  annotations:
    dns.gardener.cloud/dnsnames: "*.example.com"
    dns.gardener.cloud/class: garden
spec:
  gatewayClassName: istio
  listeners:
  - name: default
    hostname: "*.example.com"  # this is used by dns-controller-manager to extract DNS names
    port: 80
    protocol: HTTP
    allowedRoutes:
      namespaces:
        from: All
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http
  namespace: default
spec:
  parentRefs:
  - name: gateway
    namespace: istio-ingress
  hostnames: ["httpbin.example.com"]  # this is used by dns-controller-manager to extract DNS names too
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /get
    backendRefs:
    - name: httpbin
      port: 8000
EOF

You should now see events in the namespace of the gateway:

$ kubectl -n istio-system get events --sort-by={.metadata.creationTimestamp}
LAST SEEN   TYPE      REASON                 OBJECT                                       MESSAGE
...
38s         Normal    dns-annotation         service/gateway-istio                      httpbin.example.com: created dns entry object shoot--foo--bar/gateway-istio-service-zpf8n
38s         Normal    dns-annotation         service/gateway-istio                      httpbin.example.com: dns entry pending: waiting for dns reconciliation
38s         Normal    dns-annotation         service/gateway-istio                      httpbin.example.com: dns entry is pending
36s         Normal    dns-annotation         service/gateway-istio                      httpbin.example.com: dns entry active

Using a HTTPRoute as a source

If the Gateway resource is annotated with dns.gardener.cloud/dnsnames: "*", hostnames from all referencing HTTPRoute resources are automatically extracted. These resources don’t need an additional annotation.

Deploy the Gateway API configuration including a single exposed route (i.e., /get):

kubectl create namespace istio-ingress
kubectl apply -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: gateway
  namespace: istio-ingress
  annotations:
    dns.gardener.cloud/dnsnames: "*"
    dns.gardener.cloud/class: garden
spec:
  gatewayClassName: istio
  listeners:
  - name: default
    hostname: null  # not set 
    port: 80
    protocol: HTTP
    allowedRoutes:
      namespaces:
        from: All
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: http
  namespace: default
spec:
  parentRefs:
  - name: gateway
    namespace: istio-ingress
  hostnames: ["httpbin.example.com"]  # this is used by dns-controller-manager to extract DNS names too
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /get
    backendRefs:
    - name: httpbin
      port: 8000
EOF

This should show a similar events as above.

Access the sample service using `curl`

$ curl -I http://httpbin.example.com/get
HTTP/1.1 200 OK
server: istio-envoy
date: Tue, 13 Feb 2024 08:09:41 GMT
content-type: application/json
content-length: 701
access-control-allow-origin: *
access-control-allow-credentials: true
x-envoy-upstream-service-time: 19

Accessing any other URL that has not been explicitly exposed should return an HTTP 404 error:

$ curl -I http://httpbin.example.com/headers
HTTP/1.1 404 Not Found
date: Tue, 13 Feb 2024 08:09:41 GMT
server: istio-envoy
transfer-encoding: chunked