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Traffic management
Transformations
Update request paths and methods

Update request paths and methods

To update the path and HTTP method the :path and :method pseudo headers are used.

Before you begin

  1. Follow the Get started guide to install K8sGateway, set up a gateway resource, and deploy the httpbin sample app.

  2. Get the external address of the gateway and save it in an environment variable. 

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

Update request paths and HTTP methods

  1. Create a VirtualHostOption resource with your transformation rules. In the following example, you change the request path and HTTP method when a foo: bar header is present in the request.

    kubectl apply -n gloo-system -f- <<EOF
apiVersion: gateway.solo.io/v1
kind: VirtualHostOption
metadata:
  name: transformation
  namespace: gloo-system
spec:
  options:
    transformations:
      requestTransformation:
        transformationTemplate:
          headers:
            # If the foo: bar header is present, update the request path to /post. 
            # Otherwise, do not update the request path. 
            # Note that you must use the :path pseudo-header to update the request path.
            ":path":
              text: '{% if header("foo") == "bar" %}/post{% else %}{{ header(":path") }}{% endif %}'
            # If the foo: bar header is present, update the HTTP method to POST. 
            # Otherwise, do not update the HTTP method. 
            # Note that you must the :method pseudo-header to update the HTTP method of the request. 
            ":method":
              text: '{% if header("foo") == "bar" %}POST{% else %}{{ header(":method") }}{% endif %}'
  targetRefs:
  - group: gateway.networking.k8s.io
    kind: Gateway
    name: http
    namespace: gloo-system
EOF

  2. Send a request to the /get endpoint of the httpbin app. Include the foo: bar request header to trigger the request transformation. Verify that you get back a 200 HTTP response code and that your request path is rewritten to the /post endpoint. The /post endpoint accepts requests only if the HTTP POST method is used. The 200 HTTP response code therefore also indicates that the HTTP method was successfully changed from GET to POST. 

    curl -vik http://$INGRESS_GW_ADDRESS:8080/get \
 -H "foo: bar" \
 -H "host: www.example.com:8080" 
    curl -vik localhost:8080/get \
-H "foo: bar" \
-H "host: www.example.com" \

    Example output:

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    < HTTP/1.1 200 OK
HTTP/1.1 200 OK
...  
{
  "args": {},
  "headers": {
     "Accept": [
       "*/*"
     ],
     "Content-Length": [
     "0"
     ],
     "Foo": [
     "bar"
     ],
     "Host": [
     "www.example.com:8080"
     ],
     "User-Agent": [
     "curl/7.77.0"
     ],
     "X-B3-Sampled": [
     "0"
     ],
     "X-B3-Spanid": [
     "5f36d131289dba78"
     ],
     "X-B3-Traceid": [
     "590047a63783206e5f36d131289dba78"
     ],
     "X-Forwarded-Proto": [
     "http"
     ],
     "X-Request-Id": [
     "6b7debde-6a8a-4d9e-90a4-33a9a35937d3"
     ]
 },
 "origin": "127.0.0.6:48539",
 "url": "http://www.example.com:8080/post",
 "data": "",
 "files": null,
 "form": null,
 "json": null
}

  3. Send another request to the /get endpoint of the httpbin app. This time, you omit the foo: bar header. Verify that you get back a 200 HTTP response code and that the request path is not rewritten to the /post endpoint. The /get endpoint accepts requests only if the HTTP GET method is used. A 200 HTTP response code therefore also verifies that the HTTP method was not changed. 

    curl -vik http://$INGRESS_GW_ADDRESS:8080/get \
 -H "host: www.example.com:8080" 
    curl -vik localhost:8080/get \
-H "host: www.example.com" \

    Example output:

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    < HTTP/1.1 200 OK
HTTP/1.1 200 OK
...

{
 "args": {},
 "headers": {
     "Accept": [
     "*/*"
     ],
     "Host": [
     "www.example.com:8080"
     ],
     "User-Agent": [
     "curl/7.77.0"
     ],
     "X-B3-Sampled": [
     "0"
     ],
     "X-B3-Spanid": [
     "a83c35458cc4a47b"
     ],
     "X-B3-Traceid": [
     "bf14b3d3098cd639a83c35458cc4a47b"
     ],
     "X-Forwarded-Proto": [
     "http"
     ],
     "X-Request-Id": [
     "b91ecfcf-4f79-4b65-9727-09aafcaeb40e"
     ]
 },
 "origin": "127.0.0.6:46209",
 "url": "http://www.example.com:8080/get"
}

Cleanup

You can remove the resources that you created in this guide. 
kubectl delete virtualhostoption transformation -n gloo-system
Extract query parametersAdd headers to body