HTTP Request Headers
6 minute read
The HTTPRoute resource can modify the headers of a request before forwarding it to the upstream service. HTTPRoute
rules cannot use both filter types at once. Currently, Envoy Gateway only supports core HTTPRoute filters which
consist of RequestRedirect
and RequestHeaderModifier
at the time of this writing. To learn more about HTTP routing,
refer to the Gateway API documentation.
A RequestHeaderModifier
filter instructs Gateways to modify the headers in requests that match the rule
before forwarding the request upstream. Note that the RequestHeaderModifier
filter will only modify headers before the
request is sent from Envoy to the upstream service and will not affect response headers returned to the downstream
client.
Prerequisites
Follow the steps from the Quickstart to install Envoy Gateway and the example manifest. Before proceeding, you should be able to query the example backend using HTTP.
Adding Request Headers
The RequestHeaderModifier
filter can add new headers to a request before it is sent to the upstream. If the request
does not have the header configured by the filter, then that header will be added to the request. If the request 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 request.
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: RequestHeaderModifier
requestHeaderModifier:
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: RequestHeaderModifier
requestHeaderModifier:
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 upstream example app received the header add-header
with the value:
something,foo
$ curl -vvv --header "Host: headers.example" "http://${GATEWAY_HOST}/get" --header "add-header: something"
...
> GET /get HTTP/1.1
> Host: headers.example
> User-Agent: curl/7.81.0
> Accept: */*
> add-header: something
>
* 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": [
"*/*"
],
"Add-Header": [
"something",
"foo"
],
...
Setting Request Headers
Setting headers is similar to adding headers. If the request does not have the header configured by the filter, then it will be added, but unlike adding request headers which will append the value of the header if the request 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: RequestHeaderModifier
requestHeaderModifier:
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: RequestHeaderModifier
requestHeaderModifier:
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 upstream example app received the header add-header
with the original value
something
replaced by foo
.
$ curl -vvv --header "Host: headers.example" "http://${GATEWAY_HOST}/get" --header "set-header: something"
...
> GET /get HTTP/1.1
> Host: headers.example
> User-Agent: curl/7.81.0
> Accept: */*
> add-header: something
>
* 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": [
"*/*"
],
"Set-Header": [
"foo"
],
...
Removing Request Headers
Headers can be removed from a request by simply supplying a list of header names.
Setting headers is similar to adding headers. If the request does not have the header configured by the filter, then it will be added, but unlike adding request headers which will append the value of the header if the request 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: RequestHeaderModifier
requestHeaderModifier:
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: RequestHeaderModifier
requestHeaderModifier:
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 upstream example app received the header add-header
, but the header
remove-header
that was sent by curl was removed before the upstream received the request.
$ curl -vvv --header "Host: headers.example" "http://${GATEWAY_HOST}/get" --header "add-header: something" --header "remove-header: foo"
...
> GET /get HTTP/1.1
> Host: headers.example
> User-Agent: curl/7.81.0
> Accept: */*
> add-header: something
>
* 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": [
"*/*"
],
"Add-Header": [
"something"
],
...
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: RequestHeaderModifier
requestHeaderModifier:
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: RequestHeaderModifier
requestHeaderModifier:
add:
- name: "add-header-1"
value: "foo"
set:
- name: "set-header-1"
value: "bar"
remove:
- "removed-header"
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