Inject response headers

Documentation

The following example walks you through how to use an Inja template to extract a value from a request header and to add this value as a header to your responses.

Before you begin

Follow the Get started guide to install K8sGateway, 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

Inject response headers

Create a VirtualHostOption resource with your transformation rules. In the following example, you use the value from the x-solo-request request header and populate the value of that header into an x-solo-response response header.

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-solo-response:
              text: '{{ request_header("x-solo-request") }}'
  targetRefs:
  - group: gateway.networking.k8s.io
    kind: Gateway
    name: http
    namespace: gloo-system
EOF

Send a request to the httpbin app and include the x-solo-request request header. Verify that you get back a 200 HTTP response code and that the value of the x-solo-request header was added to the x-solo-response response header.

curl -vik http://$INGRESS_GW_ADDRESS:8080/response-headers \
 -H "host: www.example.com:8080" \
 -H "x-solo-request: my custom request header"

curl -vik localhost:8080/response-headers \
-H "host: www.example.com" \
-H "x-solo-request: my custom request header"

Example output:

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* Mark bundle as not supporting multiuse
< 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: *
< content-type: application/json; encoding=utf-8
content-type: application/json; encoding=utf-8
< date: Wed, 26 Jun 2024 02:54:48 GMT
date: Wed, 26 Jun 2024 02:54:48 GMT
< content-length: 3
content-length: 3
< x-envoy-upstream-service-time: 2
x-envoy-upstream-service-time: 2
< server: envoy
server: envoy
< x-envoy-decorator-operation: httpbin.httpbin.svc.cluster.local:8000/*
x-envoy-decorator-operation: httpbin.httpbin.svc.cluster.local:8000/*
< x-solo-response: my custom request header
x-solo-response: my custom request header

Cleanup

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

kubectl delete virtualhostoption transformation -n gloo-system

Decode base64 headers