Response headers

Use the ResponseHeaderModifier filter to add, append, overwrite, or remove headers from a response before it is sent back to the client.

For more information, see the HTTPHeaderFilter specification.

Before you begin

  1. Follow the Get started guide to install kgateway.

  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 kgateway-system http -o jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
echo $INGRESS_GW_ADDRESS  
    kubectl port-forward deployment/http -n kgateway-system 8080:8080

Add response headers

Add headers to incoming requests before they are sent back to the client. If the response already has the header set, the value of the header in the ResponseHeaderModifier filter is appended to the value of the header in the response.

  1. Create an HTTPRoute resource for the httpbin app with an ResponseHeaderModifier. In this example, you want to add the my-response: hello response header.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: httpbin-headers
  namespace: httpbin
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - headers.example
  rules:
    - filters:
        - type: ResponseHeaderModifier
          responseHeaderModifier:
            add: 
            - name: my-response
              value: hello
      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 ResponseHeaderModifier filter is used.
    spec.rules.filters.responseHeaderModifier.add The name and value of the response header that you want to add.
    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 headers.example domain. Verify that you get back a 200 HTTP response code and that you see the my-response header in the response. 

    curl -vi http://$INGRESS_GW_ADDRESS:8080/response-headers -H "host: headers.example:8080"
    curl -vi localhost:8080/response-headers -H "host: headers.example"

    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
< content-length: 3
content-length: 3
< x-envoy-upstream-service-time: 0
x-envoy-upstream-service-time: 0
< my-response: hello
my-response: hello
< server: envoy
server: envoy

  3. Optional: Remove the HTTPRoute that you created.

    kubectl delete httproute httpbin-headers -n httpbin

Set response headers

Setting headers is similar to adding headers. If the response does not include the header, it is added by the ResponseHeaderModifier filter. However, if the request already contains the header, its value is overwritten with the value from the ResponseHeaderModifier filter.

  1. Create an HTTPRoute resource for the httpbin app with an ResponseHeaderModifier. In this example, you want to set the my-response response header to the value custom.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: httpbin-headers
  namespace: httpbin
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - headers.example
  rules:
    - filters:
        - type: ResponseHeaderModifier
          responseHeaderModifier:
            set: 
            - name: my-response
              value: custom
      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 ResponseHeaderModifier filter is used.
    spec.rules.filters.requestHeaderModifier.set The name and value of the response header that you want to set.
    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 headers.example domain. Verify that you get back a 200 HTTP response code and that the my-response: custom header was set. 

    curl -vi http://$INGRESS_GW_ADDRESS:8080/response-headers -H "host: headers.example:8080"
    curl -vi localhost:8080/response-headers -H "host: headers.example"

    Example output:

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    ...
* 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: *
...
< my-response: custom
my-response: custom
< server: envoy
server: envoy

  3. Optional: Remove the HTTPRoute that you created.

    kubectl delete httproute httpbin-headers -n httpbin

Remove response headers

You can remove HTTP headers from a response before the response is sent back to the client.

  1. Send a request to the httpbin app and find the content-length header. 

    curl -vi http://$INGRESS_GW_ADDRESS:8080/response-headers -H "host: www.example.com:8080"
    curl -vi localhost:8080/response-headers -H "host: www.example.com"

    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
< content-length: 3
content-length: 3
< x-envoy-upstream-service-time: 0
x-envoy-upstream-service-time: 0
< server: envoy
server: envoy

  2. Create an HTTPRoute resource for the httpbin app that removes the content-length header from the response.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: httpbin-headers
  namespace: httpbin
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - headers.example
  rules:
    - filters:
        - type: ResponseHeaderModifier
          responseHeaderModifier:
            remove: 
            - content-length
      backendRefs:
        - name: httpbin
          port: 8000
EOF
    Setting Description
    spec.parentRefs The name and namespace of the gateway that servesthis 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. In this example, the ResponseHeaderModifier filter is used.
    spec.rules.filters.responseHeaderModifier.remove The name of the response header that you want to remove.
    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.

  3. Send a request to the httpbin app on the headers.example domain . Verify that the content-length response header is removed. 

    curl -vi http://$INGRESS_GW_ADDRESS:8080/response-headers -H "host: headers.example:8080"
    curl -vi localhost:8080/reesponse-headers -H "host: headers.example"

    Example output:

    * 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
< x-envoy-upstream-service-time: 0
x-envoy-upstream-service-time: 0
< server: envoy
server: envoy
< transfer-encoding: chunked
transfer-encoding: chunked

  4. Optional: Remove the HTTPRoute that you created.

    kubectl delete httproute httpbin-headers -n httpbin
Request headers