Change response status

In this guide, you learn how to use an if else function to change the HTTP status that is returned in your response. To determine the response status, you use a JSON string that is provided in the request. If the JSON includes an error, you return a 400 HTTP response code. In all other cases, you return the response code of the :status pseudo header.

Before you begin link

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
     

Change the response status link

1. Create a payload that you later send as your request body.

     cat << EOF > data.json
   {
     "error": {
      "message": "This is an error"
     }
   }
   EOF
     

2. Create a RouteOption or VirtualHostOption resource with the following transformation rules:

   • Extract the message field from the data.json file that is sent in the request.
   • If the error message is not empty, return a 400 HTTP response code in the :status pseudo header.
   • In all other cases, do not change the :status pseudo header.

       kubectl apply -f- <<EOF
     apiVersion: gateway.solo.io/v1
     kind: RouteOption
     metadata:
       name: transformation
       namespace: httpbin
     spec:
       targetRefs:
       - group: gateway.networking.k8s.io
         kind: HTTPRoute
         name: httpbin
       options:
         transformations:
           responseTransformation:
             transformationTemplate:
               extractors: 
                 message:
                   body: {}
                   mode: EXTRACT
                   regex: '[\s\S]*(message)[\s\S]*'
                   subgroup: 1
               headers:
                # We set the response status via the :status pseudo-header based on the response code
                 :status:
                   text: '{% if ( message ) != "" %}400{% else %}{{ header(":status") }}{% endif %}'
     EOF
       

       kubectl apply -n gloo-system -f- <<EOF
     apiVersion: gateway.solo.io/v1
     kind: VirtualHostOption
     metadata:
       name: transformation
       namespace: gloo-system
     spec:
       options:
         transformations:
           responseTransformation:
             transformationTemplate:
               parseBodyBehavior: ParseAsJson
               headers:
                # We set the response status via the :status pseudo-header based on the response code
                 ":status":
                   text: '{% if {{ error }} != "" %}400{% else %}{{ header(":status") }}{% endif %}'
       targetRefs:
       - group: gateway.networking.k8s.io
         kind: Gateway
         name: http
         namespace: gloo-system
     EOF
       

3. Send a request to the httpbin app and include data.json file as your payload. Because the error.message field is not empty, a 400 HTTP response code is returned.
   

     curl -X POST -H "host: www.example.com:8080" -w "%{http_code}" \
    -H "Content-Type: application/json" \
    http://$INGRESS_GW_ADDRESS:8080/post -d @data.json | jq
     

     curl -vik localhost:8080/get -w "%{http_code}" \
   -H "foo: bar" \
   -H "host: www.example.com" \
     

   Example output:

      {
        "args": {},
        "headers": {
          "Accept": [
            "*/*"
          ],
           "Content-Length": [
            "49"
          ],
          "Content-Type": [
            "application/json"
          ],
          "Host": [
            "www.example.com:8080"
          ],
          "User-Agent": [
            "curl/8.7.1"
          ],
          "X-Envoy-Expected-Rq-Timeout-Ms": [
            "15000"
          ],
          "X-Forwarded-Proto": [
            "http"
          ],
          "X-Request-Id": [
            "e462eb36-0a36-4ffd-b37d-316737819532"
          ]
        },
        "origin": "10.0.2.124:53583",
        "url": "http://www.example.com:8080/post",
        "data": "{  \"error\": {   \"message\": \"This is an error\"  }}",
        "files": null,
       "form": null,
        "json": {
          "error": {
            "message": "This is an error"
          }
        }
      }
      400
      

4. Update your payload file and remove the message so that the error field is empty.

     cat << EOF > data.json
   {
     "error": {
     }
   }
   EOF
     

5. Send another request to the httpbin app. Verify that this time a 200 HTTP response code is returned.
   

     curl -X POST -H "host: www.example.com:8080" -w "%{http_code}" \
    -H "Content-Type: application/json" \
    http://$INGRESS_GW_ADDRESS:8080/post -d @data.json | jq
     

     curl -vik localhost:8080/get -w "%{http_code}" \
   -H "foo: bar" \
   -H "host: www.example.com" \
     

   Example output:

      {
        "args": {},
        "headers": {
          "Accept": [
            "*/*"
          ],
           "Content-Length": [
            "49"
          ],
          "Content-Type": [
            "application/json"
          ],
          "Host": [
            "www.example.com:8080"
          ],
          "User-Agent": [
            "curl/8.7.1"
          ],
          "X-Envoy-Expected-Rq-Timeout-Ms": [
            "15000"
          ],
          "X-Forwarded-Proto": [
            "http"
          ],
          "X-Request-Id": [
            "e462eb36-0a36-4ffd-b37d-316737819532"
          ]
        },
        "origin": "10.0.2.124:53583",
        "url": "http://www.example.com:8080/post",
        "data": "{  \"error\": {   \"message\": \"This is an error\"  }}",
        "files": null,
       "form": null,
        "json": {
          "error": {
          }
        }
      }
      200
      

Cleanup link

You can remove the resources that you created in this guide.

  kubectl delete virtualhostoption transformation -n gloo-system
kubectl delete routeoption transformation -n httpbin