add Traffic Splitting sample (#227)

* Add traffic splitting tutorial

* Add traffic splitting tutorial

* remind the user of env vars

serving/samples/README.md

@@ -19,3 +19,4 @@ to learn more about Knative Serving resources.
 | Source to URL | A sample that shows how to use Knative to go from source code in a git repository to a running application with a URL. | [Go](source-to-url/README.md) |
 | Telemetry | This sample runs a simple web server that makes calls to other in-cluster services and responds to requests with "Hello World!". The purpose of this sample is to show generating metrics, logs, and distributed traces. | [Go](telemtry-go/README.md) |
 | Thumbnailer | An example of deploying a "dockerized" application to Knative Serving which takes video URL as an input and generates its thumbnail image. | [Go](thumbnailer-go/README.md) |
+| Traffic Splitting | This samples builds off the [Creating a RESTful Service](../rest-api-go) sample to illustrate applying a revision, then using that revision for manual traffic splitting. | [YAML](traffic-splitting/README.md) |

serving/samples/traffic-splitting/README.md

@@ -0,0 +1,103 @@
+# Simple Traffic Splitting Between Revisions
+
+This samples builds off the [Creating a RESTful Service](../rest-api-go) sample
+to illustrate applying a revision, then using that revision for manual traffic splitting.
+
+## Prerequisites
+
+1. [Creating a RESTful Service](../rest-api-go).
+
+## Updating the Service
+
+This section describes how to create an revision by deploying a new configuration.
+
+1. Replace the image reference path with our published image path in the configuration files (`serving/samples/traffic-splitting/updated_configuration.yaml`:  
+    * Manually replace:  
+     `image: github.com/knative/docs/serving/samples/rest-api-go` with `image: <YOUR_CONTAINER_REGISTRY>/serving/samples/rest-api-go`  
+
+     Or
+
+    * Use run this command:  
+     ```
+     perl -pi -e "s@github.com/knative/docs@${REPO}@g" serving/samples/rest-api-go/updated_configuration.yaml
+     ```
+
+2. Deploy the new configuration to update the `RESOURCE` environment variable
+from `stock` to `share`:
+```
+kubectl apply -f serving/samples/traffic-splitting/updated_configuration.yaml
+```
+
+3. Once deployed, traffic will shift to the new revision automatically. Verify the deployment by checking the route status:
+```
+kubectl get route -o yaml
+```
+
+4. When the new route is ready, you can access the new endpoints:  
+  The hostname and IP address can be found in the same manner as the [Creating a RESTful Service](../rest-api-go) sample:  
+  ```
+  export SERVICE_HOST=`kubectl get route stock-route-example -o jsonpath="{.status.domain}"`
+  export SERVICE_IP=`kubectl get svc knative-ingressgateway -n istio-system \
+  -o jsonpath="{.status.loadBalancer.ingress[*].ip}"`
+  ```
+
+  * Make a request to the index endpoint:
+  ```
+  curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}
+  ```
+  Response body: `Welcome to the share app!`
+
+  * Make a request to the `/share` endpoint:
+  ```
+  curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}/share
+  ```
+  Response body: `share ticker not found!, require /share/{ticker}`
+
+  * Make a request to the `/share` endpoint with a `ticker` parameter:
+  ```
+  curl --header "Host:$SERVICE_HOST" http://${SERVICE_IP}/share/<ticker>
+  ```
+  Response body: `share price for ticker <ticker>  is  <price>`
+
+## Manual Traffic Splitting
+
+This section describes how to manually split traffic to specific revisions.
+
+1. Get your revisions names via:
+```
+kubectl get revisions
+```
+```
+NAME                                AGE
+stock-configuration-example-00001   11m
+stock-configuration-example-00002   4m
+```
+
+2. Update the `traffic` list in `serving/samples/rest-api-go/sample.yaml` as:
+```yaml
+traffic:
+  - revisionName: <YOUR_FIRST_REVISION_NAME>
+    percent: 50
+  - revisionName: <YOUR_SECOND_REVISION_NAME>
+    percent: 50
+```
+
+3. Deploy your traffic revision:
+```
+kubectl apply -f serving/samples/rest-api-go/sample.yaml
+```
+
+4. Verify the deployment by checking the route status:
+```
+kubectl get route -o yaml
+```
+Once updated, you can make `curl` requests to the API using either `stock` or `share`
+endpoints.
+
+## Clean Up
+
+To clean up the sample service:
+
+```
+kubectl delete -f serving/samples/traffic-splitting/updated_configuration.yaml
+```