Direct response

Directly respond to incoming requests without routing the requests to services in your service mesh.

Rather than routing a request to a service within your service mesh, you can send back a pre-defined body and HTTP status response to the client. If necessary, you can also specify headers by using the Header Modification feature in the enclosing route.

For more information, see the Gloo Mesh Gateway API docs for route tables.

Create a virtual gateway that opens up port 80 on your ingress gateway.

  kubectl apply -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: VirtualGateway
metadata:
  name: istio-ingressgateway
  namespace: bookinfo
spec:
  workloads:
    # Matches on 'spec.selector' labels for the ingress gateway service
    - selector:
        labels:
          istio: ingressgateway
        cluster: ${CLUSTER_NAME}
  listeners:
    # The port the ingress gateway listens on for incoming requests to route
    - port:
        number: 80
      http: {}
EOF

Create a direct response route table, and specify the status and optional body that is returned. In the following example, the 510 status and no longer supported message are immediately returned in response to any requests to the /unsupported-app path.

  kubectl apply -n global -f- <<EOF
apiVersion: networking.gloo.solo.io/v2
kind: RouteTable
metadata:
  name: direct-response
  namespace: global
spec:
  hosts:
    - '*'
  # Selects the virtual gateway you previously created
  virtualGateways:
    - name: istio-ingressgateway
      namespace: bookinfo
      cluster: ${CLUSTER_NAME}
  http:
    - name: unsupported-app-route
      # Prefix matching
      matchers:
      - uri:
          prefix: /unsupported-app
      # Immediately returns this 510 response
      directResponse:
        body: '{"message": "no longer supported"}'
        status: 510
EOF

Get the external address of your ingress gateway.

  export INGRESS_GW_ADDRESS=$(kubectl get svc -n istio-ingress istio-ingressgateway -o jsonpath="{.status.loadBalancer.ingress[0]['hostname','ip']}")
echo $INGRESS_GW_ADDRESS

Verify that you receive the expected direct response by curling the ingress gateway address and, if applicable, the path. For example, the following command appends /unsupported-app.
```
  curl http://$INGRESS_GW_ADDRESS/unsupported-app
  
```