Create redirect URLs

Extract the values of common pseudo headers to generate a redirect URL.

This guide uses a subset of the supported transformation template attributes. To review all the attributes that you can set, see Templating language.

About pseudo headers

Pseudo headers are special headers that are used in HTTP/2 to provide metadata about the request or response in a structured way. Although they look like traditional HTTP/1.x headers, they come with specific characteristics:

Pseudo headers must always start with a colon (:).
They must appear before regular headers in the HTTP/2 frame.
Pseudo headers contain details about the request or response.

Common pseudo headers include:

:method: The HTTP method that is used, such as GET or POST.
:scheme: The protocol that is used, such as http or https.
:authority: The hostname and port number that the request is sent to.
:path: The path of the request.

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

Use pseudo headers for redirect URLs

Create a RouteOption or VirtualHostOption resource that defines the following transformation rules:

Build a redirect URL with the values of the :authority and :path pseudo headers. These headers are extracted from the request with the request_header function that is provided in Gloo Gateway.
The :authority pseudo header contains the hostname that the request is sent to.
The :path pseudo header is set to the request path.

The redirect URL is added to the x-forwarded-uri response header.

kubectl apply -f- <<EOF
apiVersion: gateway.solo.io/v1
kind: RouteOption
metadata:
  name: transformation
  namespace: httpbin
spec:
  targetRefs:
  - group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: httpbin
  options:
    transformations:
      responseTransformation:
        transformationTemplate:
           headers:
             x-forwarded-uri:
               text: 'https://{{ request_header(":authority") }}{{ request_header(":path") }}'
           parseBodyBehavior: "DontParse"
EOF

kubectl apply -n gloo-system -f- <<EOF
apiVersion: gateway.solo.io/v1
kind: VirtualHostOption
metadata:
  name: transformation
  namespace: gloo-system
spec:
  options:
    transformations:
      responseTransformation:
        transformationTemplate:
          headers:
            x-forwarded-uri:
              text: 'https://{{ request_header(":authority") }}{{ request_header(":path") }}'
          parseBodyBehavior: "DontParse"
  targetRefs:
  - group: gateway.networking.k8s.io
    kind: Gateway
    name: http
    namespace: gloo-system
EOF

Send a request to the httpbin app. Verify that you see the x-forwarded-uri response header that is set to the hostname and path that was used in the initial request.

curl -vik -H "host: www.example.com:8080" \
  -H "Content-Type: application/json" \
  http://$INGRESS_GW_ADDRESS:8080/response-headers

curl -vik localhost:8080/response-headers \
  -H "host: www.example.com" \
  -H "Content-Type: application/json" \

Example output:

...
* Request completely sent off
< HTTP/1.1 200 OK
HTTP/1.1 200 OK
< access-control-allow-credentials: true
access-control-allow-credentials: true
< access-control-allow-origin: *
access-control-allow-origin: *
...
< x-forwarded-uri: https://www.example.com:8080/response-headers
x-forwarded-uri: https://www.example.com:8080/response-headers
< server: envoy
server: envoy
<

Cleanup

You can remove the resources that you created in this guide.

kubectl delete virtualhostoption transformation -n gloo-system
kubectl delete routeoption transformation -n httpbin

Update request paths and methods Change response status