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Forward request URLs

Use CEL expressions to construct a full request URL from context variables and forward it upstream as a request header.

Use CEL expressions to construct a full request URL from context variables and forward it upstream as a request header. The example uses request.scheme, request.host, and request.path.

Before you begin

1. Set up an agentgateway proxy.
2. Install the httpbin sample app.

Forward the request URL upstream

In this example, you concatenate request.scheme, request.host, and request.path to build a full URL and inject it into the x-forwarded-uri request header before forwarding to the upstream service.

1. Create an AgentgatewayPolicy resource with your transformation rules.

   kubectl apply -f- <<EOF
   apiVersion: agentgateway.dev/v1alpha1
   kind: AgentgatewayPolicy
   metadata:
     name: transformation
     namespace: httpbin
   spec:
     targetRefs:
     - group: gateway.networking.k8s.io
       kind: HTTPRoute
       name: httpbin
     traffic:
       transformation:
         request:
           set:
           - name: x-forwarded-uri
             value: 'request.scheme + "://" + request.host + request.path'
   EOF

2. Send a request to the httpbin app. Verify that you get back a 200 HTTP response code and that you see the constructed URL in the x-forwarded-uri request header echoed back by httpbin.

   Cloud Provider LoadBalancerPort-forward for local testing

   curl -vi http://$INGRESS_GW_ADDRESS:80/get \
    -H "host: www.example.com:80"

   curl -vi localhost:8080/get \
   -H "host: www.example.com"

   Example output:

   ...
   < HTTP/1.1 200 OK
   HTTP/1.1 200 OK
   ...
   
   {
     "args": {},
     "headers": {
       "Accept": [
         "*/*"
       ],
       "Host": [
         "www.example.com"
       ],
       "User-Agent": [
         "curl/8.7.1"
       ],
       "X-Forwarded-Uri": [
         "http://www.example.com/get"
       ]
     },
     "origin": "10.244.0.6:59296",
     "url": "http://www.example.com/get"
   }
   

Cleanup

kubectl delete AgentgatewayPolicy transformation -n httpbin