In this guide, you explore how to use the headersToAppend transformation template attribute to add multiple values to the same header. The values are separated with a comma.

Before you begin

  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 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

Append headers

  1. Create a GlooTrafficPolicy with the following transformation rules:

    • Extract the value of the Host request header and use this value to build the customcookie2 string. Then, append the transformed string to the Set-Cookie request header.
    • Extract the value of the Host request header and use this value to build the customcookie3 string. Then, append the transformed string to the same Set-Cookie request header.
      kubectl apply -f- <<EOF
apiVersion: gloo.solo.io/v1alpha1
kind: GlooTrafficPolicy
metadata:
  name: transformation
  namespace: httpbin
spec:
  targetRefs: 
  - group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: httpbin
  glooTransformation:
    stages:
      early: 
        requests: 
        - transformation: 
            template: 
              headersToAppend: 
              - key: Set-Cookie
                value: 'customcookie2={{ request_header("Host") }}'
              - key: Set-Cookie
                value: 'customcookie3={{ request_header("Host") }}'
EOF

  2. Send a request to the httpbin app. Verify that you see multiple values in the Set-Cookie request header.

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

    Example output:

       {
     "headers": {
       "Accept": [
        "*/*"
       ],
       "Host": [
         "www.example.com:8080"
       ],
       "Set-Cookie": [
         "customcookie2=www.example.com:8080",
         "customcookie3=www.example.com:8080"
       ],
       "User-Agent": [
         "curl/8.7.1"
       ],
       "X-Envoy-Expected-Rq-Timeout-Ms": [
         "15000"
       ],
       "X-Forwarded-Proto": [
         "http"
       ],
       "X-Request-Id": [
         "09fbe5ed-5060-4cf5-835c-46729bf100db"
       ]
     }
   }

Cleanup

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

  kubectl delete glootrafficpolicy transformation -n httpbin