Replace the host header value before forwarding a request to a backend service by using the URLRewrite filter.

For more information, see the Kubernetes Gateway API documentation.

Before you begin link

1. Follow the Get started guide to install Gloo Gateway.

2. Follow the Sample app guide to create a gateway proxy with an HTTP listener and deploy the httpbin sample app.

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

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

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

In-cluster service host rewrites link

1. Create an HTTPRoute resource for the httpbin app that uses the URLRewrite filter to rewrite the hostname of th request. In this example, all incoming requests on the rewrite.example domain are rewritten to the www.example.com host.

     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: URLRewrite
            urlRewrite:
              hostname: "www.example.com"
          backendRefs:
           - name: httpbin
             port: 8000
   EOF
     

   Setting	Description
   spec.parentRefs	The name and namespace of the Gateway that serves this HTTPRoute. In this example, you use the http gateway that was created as part of the get started guide.
   spec.rules.filters.type	The type of filter that you want to apply to incoming requests. In this example, the URLRewrite filter is used.
   spec.rules.filters.urlRewrite.hostname	The hostname that you want to rewrite requests to.
   spec.rules.backendRefs	The backend destination you want to forward traffic to. In this example, all traffic is forwarded to the httpbin app that you set up as part of the get started guide.

2. 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.

   info

   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 -vi http://$INGRESS_GW_ADDRESS:8080/headers -H "host: rewrite.example:8080"
     

     curl -vi 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"
      ]
    }
   }
     

External service host rewrites link

1. Create a Backend that represents your external service. The following example creates a Backend for the httpbin.org domain.

     kubectl apply -f- <<EOF
   apiVersion: gateway.kgateway.dev/v1alpha1
   kind: Backend
   metadata:
     name: httpbin
     namespace: default
   spec:
     type: Static
     static:
       hosts:
         - host: httpbin.org
           port: 80
   EOF
     

2. Create an HTTPRoute resource that matches incoming traffic on the external-rewrite.example domain and forwards traffic to the Backend that you created. Because the Backend expects a different domain, you use the URLRewrite filter to rewrite the hostname from external-rewrite.example to httpbin.org.

     kubectl apply -f- <<EOF
   apiVersion: gateway.networking.k8s.io/v1
   kind: HTTPRoute
   metadata:
     name: backend-rewrite
     namespace: default
   spec:
     parentRefs:
     - name: http
       namespace: gloo-system
     hostnames:
       - external-rewrite.example
     rules:
        - filters:
          - type: URLRewrite
            urlRewrite:
              hostname: "httpbin.org"
          backendRefs:
          - name: httpbin
            kind: Backend
            group: gateway.kgateway.dev
   EOF
     

3. Send a request to the external-rewrite.example domain. Verify that you get back a 200 HTTP response code and that you see the Host: httpbin.org header in your response.

     curl -vi http://$INGRESS_GW_ADDRESS:8080/headers -H "host: external-rewrite.example:8080"
     

     curl -vi localhost:8080/headers -H "host: external-rewrite.example"
     

   Example output:

     * Request completely sent off
   < HTTP/1.1 200 OK
   HTTP/1.1 200 OK
   < content-type: application/json
   content-type: application/json
   < content-length: 268
   content-length: 268
   < server: envoy
   server: envoy
   < access-control-allow-origin: *
   access-control-allow-origin: *
   < access-control-allow-credentials: true
   access-control-allow-credentials: true
   < x-envoy-upstream-service-time: 2416
   x-envoy-upstream-service-time: 2416
   < 
   
   {
     "headers": {
       "Accept": "*/*", 
       "Host": "httpbin.org", 
       "User-Agent": "curl/8.7.1", 
       "X-Amzn-Trace-Id": "Root=1-6859932a-1fb1dc706dadcc183b407d4d", 
       "X-Envoy-Expected-Rq-Timeout-Ms": "15000", 
      "X-Envoy-External-Address": "10.0.15.215"
     }
   }   
     

Cleanup link

  kubectl delete httproute httpbin-rewrite -n httpbin
kubectl delete httproute backend-rewrite 
kubectl delete backend httpbin
  

link