Path rewrites

Rewrite path prefixes in requests by using the URLRewrite filter.

For more information, see the Kubernetes Gateway API documentation.

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

Rewrite prefix path

Use the HTTPPathModifier to rewrite path prefixes.

In-custer services

  1. Create an HTTPRoute resource for the httpbin app that configures an URLRewrite filter to rewrite prefix paths. In this example, all incoming requests that match the /headers prefix path on the rewrite.example domain are rewritten to the /anything prefix path.

    Because the ReplacePrefixPath path modifier is used, only the path prefix is replaced during the rewrite. For example, requests to http://rewrite.example/headers are rewritten to https://rewrite.example/anything. However, for longer paths, such as in http://rewrite.example/headers/200, only the prefix is replaced and the path is rewritten to http://rewrite.example/anything/200.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: httpbin-rewrite
  namespace: httpbin
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - rewrite.example
  rules:
    - matches:
      - path:
          type: PathPrefix
          value: /headers
      filters:
        - type: URLRewrite
          urlRewrite:
            path:
              type: ReplacePrefixMatch
              replacePrefixMatch: /anything
      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 URLRewrite filter is used.
    spec.rules.filters.urlRewrite.path.type The type of HTTPPathModifier that you want to use. In this example, ReplacePrefixMatch is used, which replaces only the path prefix.
    spec.rules.filters.urlRewrite.path.replacePrefixMatch The path prefix you want to rewrite to. In this example, you replace the prefix path with the /anything prefix path.
    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 along the /headers path on the rewrite.example domain. Verify that you get back a 200 HTTP response code and that your request is rewritten to the /anything path. 

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

    Example output:

    ...
"origin": "10.0.9.36:50660",
"url": "http://rewrite.example:8080/anything",
"data": "",
"files": null,
"form": null,
"json": null
...

  3. Send another request to the httpbin app. This time, you send it along the /headers/200 path on the rewrite.example domain. Verify that you get back a 200 HTTP response code and that your request path is rewritten to /anything/200.

    curl -vi http://$INGRESS_GW_ADDRESS:8080/headers/200 -H "host: rewrite.example:8080"
    curl -vi localhost:8080/headers/200 -H "host: rewrite.example"

    Example output:

    ...
"origin": "10.0.9.36:50660",
"url": "http://rewrite.example:8080/anything/200",
"data": "",
"files": null,
"form": null,
"json": null
...

External services

  1. Create a Backend that represents your external service. The following example creates a Backend for the httpbin.org domain.

    kubectl apply -f- <<EOF
apiVersion: gateway.kgateway.dev/v1alpha1
kind: Backend
metadata:
  name: httpbin
  namespace: default
spec:
  type: Static
  static:
    hosts:
      - host: httpbin.org
        port: 80
EOF

  2. Create an HTTPRoute resource that matches incoming traffic on the /headers path for the external-rewrite.example domain and forwards traffic to the Backend that you created. Because the Backend expects a different domain, you use the URLRewrite filter to rewrite the hostname from external-rewrite.example to httpbin.org. In addition, you rewrite the /headers path prefix to /anything.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: backend-rewrite
  namespace: default
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - external-rewrite.example
  rules:
     - matches:
       - path:
           type: PathPrefix
           value: /headers
       filters:
       - type: URLRewrite
         urlRewrite:
           hostname: "httpbin.org"
           path: 
             type: ReplacePrefixMatch
             replacePrefixMatch: /anything   
       backendRefs:
       - name: httpbin
         kind: Backend
         group: gateway.kgateway.dev
EOF

  3. Send a request to the external-rewrite.example domain on the /headers path. Verify that you get back a 200 HTTP response code and that the request was rewritten to httpbin.org/anything.

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

    Example output:

    * Request completely sent off
< HTTP/1.1 200 OK
HTTP/1.1 200 OK
< content-type: application/json
content-type: application/json
< content-length: 268
content-length: 268
< server: envoy
server: envoy
< access-control-allow-origin: *
access-control-allow-origin: *
< access-control-allow-credentials: true
access-control-allow-credentials: true
< x-envoy-upstream-service-time: 2416
x-envoy-upstream-service-time: 2416
< 

{
  "args": {}, 
  "data": "", 
 "files": {}, 
  "form": {}, 
  "headers": {
    "Accept": "*/*", 
    "Host": "httpbin.org", 
    "User-Agent": "curl/8.7.1", 
    "X-Amzn-Trace-Id": "Root=1-68599cdc-5d3c0d9a1ac2aa482effb24b", 
    "X-Envoy-Expected-Rq-Timeout-Ms": "15000", 
    "X-Envoy-External-Address": "10.0.15.215", 
    "X-Envoy-Original-Path": "/"
  }, 
  "json": null, 
  "method": "GET", 
  "url": "http://httpbin.org/anything"
}

Rewrite full path

Use the HTTPPathModifier to rewrite full paths.

In-cluster services

  1. Create an HTTPRoute resource for the httpbin app that configures an URLRewrite filter to rewrite prefix paths. In this example, all incoming requests that match the /headers prefix path on the rewrite.example domain are rewritten to /anything.

    Because the ReplaceFullPath path modifier is used, requests to http://rewrite.example/headers and http://rewrite.example/headers/200 both are rewritten to https://rewrite.example/anything.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: httpbin-rewrite
  namespace: httpbin
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - rewrite.example
  rules:
    - matches:
      - path:
          type: PathPrefix
          value: /headers
      filters:
        - type: URLRewrite
          urlRewrite:
            path:
              type: ReplaceFullPath
              replaceFullPath: /anything
      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 URLRewrite filter is used.
    spec.rules.filters.urlRewrite.path.type The type of HTTPPathModifier that you want to use. In this example, ReplaceFullPath is used, which replaces the full path prefix.
    spec.rules.filters.urlRewrite.path.replaceFullPath The path prefix you want to rewrite to. In this example, you replace the full prefix path with the /anything prefix path.
    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 along the /headers path on the rewrite.example domain. Verify that you get back a 200 HTTP response code and that your request is rewritten to the /anything path. 

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

    Example output:

    ...
"origin": "10.0.9.36:50660",
"url": "http://rewrite.example:8080/anything",
"data": "",
"files": null,
"form": null,
"json": null
...

  3. Send another request to the httpbin app. This time, you send it along the /headers/200 path on the rewrite.example domain. Verify that you also get back a 200 HTTP response code and that the full path is rewritten to the /anything path. 

    curl -vi http://$INGRESS_GW_ADDRESS:8080/headers/200 -H "host: rewrite.example:8080"
    curl -vi localhost:8080/headers/200 -H "host: rewrite.example"

    Example output:

    ...
"origin": "10.0.9.36:50660",
"url": "http://rewrite.example:8080/anything",
"data": "",
"files": null,
"form": null,
"json": null
...

External services

  1. Create a Backend that represents your external service. The following example creates a Backend for the httpbin.org domain.

    kubectl apply -f- <<EOF
apiVersion: gateway.kgateway.dev/v1alpha1
kind: Backend
metadata:
  name: httpbin
  namespace: default
spec:
  type: Static
  static:
    hosts:
      - host: httpbin.org
        port: 80
EOF

  2. Create an HTTPRoute resource that matches incoming traffic on the external-rewrite.example domain and forwards traffic to the Backend that you created. Because the Backend expects a different domain, you use the URLRewrite filter to rewrite the hostname from external-rewrite.example to httpbin.org. In addition, you rewrite any existing paths to /anything.

    kubectl apply -f- <<EOF
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: backend-rewrite
  namespace: default
spec:
  parentRefs:
  - name: http
    namespace: kgateway-system
  hostnames:
    - external-rewrite.example
  rules:
     - filters:
       - type: URLRewrite
         urlRewrite:
           hostname: "httpbin.org"
           path:
             type: ReplaceFullPath
             replaceFullPath: /anything 
       backendRefs:
       - name: httpbin
         kind: Backend
         group: gateway.kgateway.dev
EOF

  3. Send a request to the external-rewrite.example domain on the /header path. Verify that you get back a 200 HTTP response code and that the request was rewritten to httpbin.org/anything.

    curl -vi http://$INGRESS_GW_ADDRESS:8080/header -H "host: external-rewrite.example:8080"
    curl -vi localhost:8080/header -H "host: external-rewrite.example"

    Example output:

    * Request completely sent off
< HTTP/1.1 200 OK
HTTP/1.1 200 OK
< content-type: application/json
content-type: application/json
< content-length: 268
content-length: 268
< server: envoy
server: envoy
< access-control-allow-origin: *
access-control-allow-origin: *
< access-control-allow-credentials: true
access-control-allow-credentials: true
< x-envoy-upstream-service-time: 2416
x-envoy-upstream-service-time: 2416
< 

{
  "args": {}, 
  "data": "", 
 "files": {}, 
  "form": {}, 
  "headers": {
    "Accept": "*/*", 
    "Host": "httpbin.org", 
    "User-Agent": "curl/8.7.1", 
    "X-Amzn-Trace-Id": "Root=1-68599cdc-5d3c0d9a1ac2aa482effb24b", 
    "X-Envoy-Expected-Rq-Timeout-Ms": "15000", 
    "X-Envoy-External-Address": "10.0.15.215", 
    "X-Envoy-Original-Path": "/"
  }, 
  "json": null, 
  "method": "GET", 
  "url": "http://httpbin.org/anything"
}

Cleanup

You can remove the resources that you created in this guide. 
kubectl delete httproute httpbin-rewrite -n httpbin
Host rewrites