HTTP Response Header Manipulate
The HTTP header manipulation feature allows you to fine-tune incoming and outgoing request and response headers.
In Gateway API, the HTTPRoute resource utilities two HTTPHeaderFilter filter for request and response header manipulation.
The both filters supports add, set and remove operation. The combination of them is also available.
This document will introduce the HTTP response header manipulation function of FSM Gateway. The introduction of HTTP request header manipulation is located in doc HTTP Request Header Manipulate.
Prerequisites
- Kubernetes cluster version v1.21.0 or higher.
- kubectl CLI
- FSM Gateway installed via guide doc.
Demonstration
We will follow the sample in HTTP Routing.
In backend service responds the generated headers as below.=
curl -I -H 'host:foo.example.com' http://$GATEWAY_IP:8000/headers
HTTP/1.1 200 OK
server: gunicorn/19.9.0
date: Tue, 21 Nov 2023 08:54:43 GMT
content-type: application/json
content-length: 106
access-control-allow-origin: *
access-control-allow-credentials: true
connection: keep-alive
Add HTTP Response header
With header adding feature, let’s try to add a new header to response by add HTTPHeaderFilter filter.
Modifying the HTTPRoute http-route-foo and add ResponseHeaderModifier filter.
kubectl apply -n httpbin -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-route-foo
spec:
parentRefs:
- name: simple-fsm-gateway
port: 8000
hostnames:
- foo.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: httpbin
port: 8080
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
add:
- name: "header-2-add"
value: "foo"
EOF
Now request the path /headers again and you will get the new header in response injected by gateway.
curl -I -H 'host:foo.example.com' http://$GATEWAY_IP:8000/headers
HTTP/1.1 200 OK
server: gunicorn/19.9.0
date: Tue, 21 Nov 2023 08:56:58 GMT
content-type: application/json
content-length: 139
access-control-allow-origin: *
access-control-allow-credentials: true
header-2-add: foo
connection: keep-alive
Set HTTP Response header
set operation is used to update the value of specified header. If the header not exist, it will do as add operation.
Let’s update the HTTPRoute resource again and set two headers with new value. One does not exist and another does.
kubectl apply -n httpbin -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-route-foo
spec:
parentRefs:
- name: simple-fsm-gateway
port: 8000
hostnames:
- foo.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: httpbin
port: 8080
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
set:
- name: "header-2-set"
value: "foo"
- name: "server"
value: "fsm/gateway"
EOF
In the response, we can get the two headers updated.
curl -I -H 'host:foo.example.com' http://$GATEWAY_IP:8000/headers
HTTP/1.1 200 OK
server: fsm/gateway
date: Tue, 21 Nov 2023 08:58:56 GMT
content-type: application/json
content-length: 139
access-control-allow-origin: *
access-control-allow-credentials: true
header-2-set: foo
connection: keep-alive
Remove HTTP Response header
The last operation is remove, which can remove the header of client sending.
Let’s update the HTTPRoute resource to remove server header directly to hide backend implementation from client.
kubectl apply -n httpbin -f - <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
name: http-route-foo
spec:
parentRefs:
- name: simple-fsm-gateway
port: 8000
hostnames:
- foo.example.com
rules:
- matches:
- path:
type: PathPrefix
value: /
backendRefs:
- name: httpbin
port: 8080
filters:
- type: ResponseHeaderModifier
responseHeaderModifier:
remove:
- "server"
EOF
With resource udpated, the backend server implementation is invisible on client side.
curl -I -H 'host:foo.example.com' http://$GATEWAY_IP:8000/headers
HTTP/1.1 200 OK
date: Tue, 21 Nov 2023 09:00:32 GMT
content-type: application/json
content-length: 139
access-control-allow-origin: *
access-control-allow-credentials: true
connection: keep-alive
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