feat: Update NGF demo README to make it standalone (#20)

Author: sjberman

nginx-gateway-fabric/appworld/README.md

@@ -1,15 +1,112 @@
 # NGINX Gateway Fabric Demo
 
-This demo contains the files used in the NGINX Gateway Fabric AppWorld demo.
+In this demo we will deploy NGINX Gateway Fabric and configure traffic splitting for a simple cafe application.
+We will use HTTPRoute resources to split traffic between two versions of the application -- `coffee-v1`
+and `coffee-v2`.
 
-To install the Gateway API CRDs:
+
+## Running the Example
+
+## 1. Deploy NGINX Gateway Fabric
+
+1. Follow the [installation instructions](https://docs.nginx.com/nginx-gateway-fabric/installation/) to deploy NGINX Gateway Fabric.
+
+1. Save the public IP address of NGINX Gateway Fabric into a shell variable:
+
+   ```text
+   GW_IP=XXX.YYY.ZZZ.III
+   ```
+
+1. Save the port of NGINX Gateway Fabric:
+
+   ```text
+   GW_PORT=<port number>
+   ```
+
+This assumes that you have an accessible external IP address. If not, you can port-forward the nginx service to localhost and access it using `127.0.0.1:8080` instead.
 
 ```shell
-kubectl kustomize "https://github.com/nginx/nginx-gateway-fabric/config/crd/gateway-api/standard?ref=v1.6.1" | kubectl apply -f -
+kubectl -n nginx-gateway port-forward svc/<ngf-service-name> 8080:80 &
 ```
 
-To install NGINX Gateway Fabric:
+## 2. Deploy the Coffee Application
+
+1. Create the Cafe Deployments and Services:
+
+   ```shell
+   kubectl apply -f coffee-app.yaml
+   ```
+
+1. Check that the Pods are running in the `default` Namespace:
+
+   ```shell
+   kubectl get pods
+   ```
+
+   ```text
+   NAME                         READY   STATUS    RESTARTS   AGE
+   coffee-v1-7c57c576b-rfjsh    1/1     Running   0          21m
+   coffee-v2-698f66dc46-vcb6r   1/1     Running   0          21m
+   ```
+
+## 3. Configure Routing
+
+1. Create the Gateway:
+
+   ```shell
+   kubectl apply -f gateway.yaml
+   ```
+
+1. Create the HTTPRoute resource:
+
+   ```shell
+   kubectl apply -f cafe-route.yaml
+   ```
+
+This HTTPRoute resource defines a route for the path `/coffee` that sends 80% of the requests to `coffee-v1` and 20%
+to `coffee-v2`. In this example, we use 80 and 20; however, the weights are calculated proportionally and do not need to
+sum to 100. For example, the weights of 8 and 2, 16 and 4, or 32 and 8 all evaluate to the same relative proportions.
+
+## 4. Test the Application
+
+To access the application, we will use `curl` to send requests to `/coffee`:
 
 ```shell
-helm install ngf oci://ghcr.io/nginx/charts/nginx-gateway-fabric --create-namespace -n nginx-gateway
+curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee
+```
+
+80% of the responses will come from `coffee-v1`:
+
+```text
+Server address: 10.12.0.18:80
+Server name: coffee-v1-7c57c576b-rfjsh
+```
+
+20% of the responses will come from `coffee-v2`:
+
+```text
+Server address: 10.12.0.19:80
+Server name: coffee-v2-698f66dc46-vcb6r
 ```
+
+### 5. Modify the Traffic Split Configuration
+
+Let's shift more of the traffic to `coffee-v2`. To do this we will update the HTTPRoute resource and change the weight
+of the `coffee-v2` backend to 80. Backends with equal weights will receive an equal share of traffic.
+
+1. Apply the updated HTTPRoute resource:
+
+   ```shell
+   kubectl apply -f cafe-route-equal-weight.yaml
+   ```
+
+2. Test the application again:
+
+   ```shell
+   curl --resolve cafe.example.com:$GW_PORT:$GW_IP http://cafe.example.com:$GW_PORT/coffee
+   ```
+
+The responses will now be split evenly between `coffee-v1` and `coffee-v2`.
+
+We can continue modifying the weights of the backends to shift more and more traffic to `coffee-v2`.`cafe-route-v2.yaml` will shift 100% of traffic to `coffee-v2`.
+If there's an issue with `coffee-v2`, we can quickly shift traffic back to `coffee-v1`.

nginx-gateway-fabric/appworld/cafe-route-equal-weight.yaml

@@ -16,7 +16,7 @@ spec:
     backendRefs:
     - name: coffee-v1
       port: 80
-      weight: 50
+      weight: 80
     - name: coffee-v2
       port: 80
-      weight: 50
+      weight: 80