HTTP Response Headers
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The HTTPRoute resource can modify the headers of a response before responding it to the downstream service. To learn more about HTTP routing, refer to the Gateway API documentation.
A ResponseHeaderModifier filter instructs Gateways to modify the headers in responses that match the
rule before responding to the downstream. Note that the ResponseHeaderModifier filter will only modify headers before
the response is returned from Envoy to the downstream client and will not affect request headers forwarding to the
upstream service.
Prerequisites
Follow the steps from the Quickstart task to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.
Verify the Gateway status:
kubectl get gateway/eg -o yaml
egctl x status gateway -v
Adding Response Headers
The ResponseHeaderModifier filter can add new headers to a response before it is sent to the upstream. If the response
does not have the header configured by the filter, then that header will be added to the response. If the response
already has the header configured by the filter, then the value of the header in the filter will be appended to the
value of the header in the response.
cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- group: ""
kind: Service
name: backend
port: 3000
weight: 1
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
add:
- name: "add-header"
value: "foo"
EOF
Save and apply the following resource to your cluster:
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- group: ""
kind: Service
name: backend
port: 3000
weight: 1
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
add:
- name: "add-header"
value: "foo"
The HTTPRoute status should indicate that it has been accepted and is bound to the example Gateway.
kubectl get httproute/http-headers -o yaml
Get the Gateway’s address:
export GATEWAY_HOST=$(kubectl get gateway/eg -o jsonpath='{.status.addresses[0].value}')
Querying headers.example/get should result in a 200 response from the example Gateway and the output from the
example app should indicate that the downstream client received the header add-header with the value: foo
$ curl -vvv --header "Host: headers.example" "http://${GATEWAY_HOST}/get" -H 'X-Echo-Set-Header: X-Foo: value1'
...
> GET /get HTTP/1.1
> Host: headers.example
> User-Agent: curl/7.81.0
> Accept: */*
> X-Echo-Set-Header: X-Foo: value1
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-type: application/json
< x-content-type-options: nosniff
< content-length: 474
< x-envoy-upstream-service-time: 0
< server: envoy
< x-foo: value1
< add-header: foo
<
...
"headers": {
"Accept": [
"*/*"
],
"X-Echo-Set-Header": [
"X-Foo: value1"
]
...
Setting Response Headers
Setting headers is similar to adding headers. If the response does not have the header configured by the filter, then it will be added, but unlike adding response headers which will append the value of the header if the response already contains it, setting a header will cause the value to be replaced by the value configured in the filter.
cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- backendRefs:
- group: ""
kind: Service
name: backend
port: 3000
weight: 1
matches:
- path:
type: PathPrefix
value: /
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
set:
- name: "set-header"
value: "foo"
EOF
Save and apply the following resource to your cluster:
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- backendRefs:
- group: ""
kind: Service
name: backend
port: 3000
weight: 1
matches:
- path:
type: PathPrefix
value: /
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
set:
- name: "set-header"
value: "foo"
Querying headers.example/get should result in a 200 response from the example Gateway and the output from the
example app should indicate that the downstream client received the header set-header with the original value value1
replaced by foo.
$ curl -vvv --header "Host: headers.example" "http://${GATEWAY_HOST}/get" -H 'X-Echo-Set-Header: set-header: value1'
...
> GET /get HTTP/1.1
> Host: headers.example
> User-Agent: curl/7.81.0
> Accept: */*
> X-Echo-Set-Header: set-header: value1
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-type: application/json
< x-content-type-options: nosniff
< content-length: 474
< x-envoy-upstream-service-time: 0
< server: envoy
< set-header: foo
<
"headers": {
"Accept": [
"*/*"
],
"X-Echo-Set-Header": [
"set-header": value1"
]
...
Removing Response Headers
Headers can be removed from a response by simply supplying a list of header names.
Setting headers is similar to adding headers. If the response does not have the header configured by the filter, then it will be added, but unlike adding response headers which will append the value of the header if the response already contains it, setting a header will cause the value to be replaced by the value configured in the filter.
cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- group: ""
name: backend
port: 3000
weight: 1
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
remove:
- "remove-header"
EOF
Save and apply the following resource to your cluster:
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- group: ""
name: backend
port: 3000
weight: 1
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
remove:
- "remove-header"
Querying headers.example/get should result in a 200 response from the example Gateway and the output from the
example app should indicate that the header remove-header that was sent by curl was removed before the upstream
received the response.
$ curl -vvv --header "Host: headers.example" "http://${GATEWAY_HOST}/get" -H 'X-Echo-Set-Header: remove-header: value1'
...
> GET /get HTTP/1.1
> Host: headers.example
> User-Agent: curl/7.81.0
> Accept: */*
> X-Echo-Set-Header: remove-header: value1
>
* Mark bundle as not supporting multiuse
< HTTP/1.1 200 OK
< content-type: application/json
< x-content-type-options: nosniff
< content-length: 474
< x-envoy-upstream-service-time: 0
< server: envoy
<
"headers": {
"Accept": [
"*/*"
],
"X-Echo-Set-Header": [
"remove-header": value1"
]
...
Combining Filters
Headers can be added/set/removed in a single filter on the same HTTPRoute and they will all perform as expected
cat <<EOF | kubectl apply -f -
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- group: ""
kind: Service
name: backend
port: 3000
weight: 1
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
add:
- name: "add-header-1"
value: "foo"
set:
- name: "set-header-1"
value: "bar"
remove:
- "removed-header"
EOF
Save and apply the following resource to your cluster:
---
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-headers
spec:
parentRefs:
- name: eg
hostnames:
- headers.example
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- group: ""
kind: Service
name: backend
port: 3000
weight: 1
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
add:
- name: "add-header-1"
value: "foo"
set:
- name: "set-header-1"
value: "bar"
remove:
- "removed-header"
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