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Configuring Gateway API resources across namespaces

Unlike Ingress, Gateway API routing resources can use Services in another namespace if the Service’s namespace permits it. This guide shows how to create a HTTPRoute in one namespace that routes to a Service in another, bound to a Gateway in a third namespace.

Create namespaces and allow references

1. Create separate namespaces to hold the HTTPRoute and target Service:

   kubectl create namespace test-source
   kubectl create namespace test-destination
   

   The results should look like this:

   namespace/test-source created
   namespace/test-destination created
   

2. Create a ReferenceGrant resource in the destination namespace:

   echo 'kind: ReferenceGrant
   apiVersion: gateway.networking.k8s.io/v1beta1    
   metadata:                                    
     name: test-grant
     namespace: test-destination
   spec:                        
     from:
     - group: gateway.networking.k8s.io
       kind: HTTPRoute                 
       namespace: test-source
     to:                     
     - group: ""
       kind: Service
   ' | kubectl create -f -
   

   The results should look like this:

   referencegrant.gateway.networking.k8s.io/test-grant created
   

ReferenceGrants allow namespaces to opt in to references from other resources. They reside in the namespace of the target resource and list resources and namespaces that can talk to specific resources in the ReferenceGrant’s namespace. The above example allows HTTPRoutes in the test-source namespace to reference Services in the test-destination namespace.

Using a Gateway resource in a different namespace

Gateway resources may also allow references from resources (HTTPRoute, TCPRoute, etc.) in other namespaces. However, these references do not use ReferenceGrants, as they are defined per listener in the Gateway resource, not for the entire Gateway. A listener’s allowedRoutes field lets you define which routing resources can bind to that listener.

The default Gateway in this guide only allows routes from its same namespace (default). You’ll need to expand its scope to allow routes from the test-source namespace:

kubectl patch --type=json gateways.gateway.networking.k8s.io kong -p='[{"op":"replace","path": "/spec/listeners/0/allowedRoutes/namespaces/from","value":"All"}]'

The results should look like this:

gateway.gateway.networking.k8s.io/kong patched

This results in a Gateway resource with the following configuration:

apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: kong
spec:
  gatewayClassName: kong
  listeners:
  - name: proxy
    port: 80
    protocol: HTTP
    allowedRoutes:
      namespaces:
        from: All

Listeners can allow routes in their own namespace (from: Same), all namespaces (from: All), or a labeled set of namespaces (from: Selector).

Deploy a Service and HTTPRoute

1. Deploy an echo Service to the test-destination resource.

   kubectl apply -f https://docs.konghq.com/assets/kubernetes-ingress-controller/examples/echo-service.yaml -n test-destination
   

   The results should look like this:

   service/echo created
   deployment.apps/echo created
   

2. Deploy a HTTPRoute that sends traffic to the service.

   echo 'apiVersion: gateway.networking.k8s.io/v1
   kind: HTTPRoute
   metadata:
     name: echo
     namespace: test-source
     annotations:
       konghq.com/strip-path: "true"
   spec:
     parentRefs:
     - name: kong
       namespace: default
     rules:
     - matches:
       - path:
           type: PathPrefix
           value: /echo
       backendRefs:
       - name: echo
         kind: Service
         port: 1027
         namespace: test-destination
   ' | kubectl apply -f -
   

   The results should look like this:

   httproute.gateway.networking.k8s.io/echo created
   

   Note the namespace fields in both the parent and backend references. By default, entries here attempt to use the same namespace as the HTTPRoute if you do not specify a namespace.

3. Send requests through the route.

   curl -s "$PROXY_IP/echo"
   

   The results should look like this:

   Welcome, you are connected to node kind-control-plane.
   Running on Pod echo-965f7cf84-z9jv2.
   In namespace test-destination.
   With IP address 10.244.0.6.