Host rewrites

Replace the host header value before forwarding a request to a backend service.

For more information, see the Kubernetes Gateway API documentation.

Before you begin

Follow the Get started guide to install Gloo Gateway, set up a gateway resource, and deploy the httpbin sample app.

Get the external address of the gateway and save it in an environment variable.

export INGRESS_GW_ADDRESS=$(kubectl get svc -n gloo-system gloo-proxy-http -o jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
echo $INGRESS_GW_ADDRESS

kubectl port-forward deployment/gloo-proxy-http -n gloo-system 8080:8080

Rewrite hosts

Path rewrites use the HTTP path modifier to rewrite path prefixes.

Create a RouteOption resource to define your rewrite rules. In the following example the host request header is rewritten to the www.example.com host.

kubectl apply -n httpbin -f- <<EOF
apiVersion: gateway.solo.io/v1
kind: RouteOption
metadata:
  name: rewrite
  namespace: httpbin
spec:
  options:
    hostRewrite: 'www.example.com'
EOF

Create an HTTPRoute resource for the httpbin app that references the RouteOption resource that you created. In this example, all incoming requests on the rewrite.example domain are rewritten to the www.example.com host as defined in the referenced RouteOption resource.

kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: httpbin-rewrite
  namespace: httpbin
spec:
  parentRefs:
  - name: http
    namespace: gloo-system
  hostnames:
    - rewrite.example
  rules:
     - filters:
       - type: ExtensionRef
         extensionRef:
           group: gateway.solo.io
           kind: RouteOption
           name: rewrite
       backendRefs:
        - name: httpbin
          port: 8000
EOF

Send a request to the httpbin app on the rewrite.example domain. Verify that you get back a 200 HTTP response code and that you see the Host: www.example.com header in your response.
The following request returns a 200 HTTP response code, because you set up an HTTPRoute for the httpbin app on the www.example.com domain as part of the Getting started guide. If you chose a different domain for your example, make sure that you have an HTTPRoute that can be reached under the host you want to rewrite to.
curl -vik http://$INGRESS_GW_ADDRESS:8080/headers -H "host: rewrite.example:8080"
curl -vik localhost:8080/headers -H "host: rewrite.example"
Example output:
```
...
{
 "headers": {
   "Accept": [
     "*/*"
   ],
   "Host": [
     "www.example.com"
   ],
   "User-Agent": [
     "curl/7.77.0"
   ],
   "X-Envoy-Expected-Rq-Timeout-Ms": [
     "15000"
   ],
   "X-Forwarded-Proto": [
     "http"
   ],
   "X-Request-Id": [
     "ffc55a3e-60ae-4c90-9a5c-62c8a1ba1076"
   ]
 }
}
```

Optional: Clean up the resources that you created.

kubectl delete routeoption rewrite -n httpbin
kubectl delete httproute httpbin-rewrite -n httpbin

Path rewrites