Configuring Request Routing

This task shows you how to route requests dynamically to multiple versions of a microservice.

Before you begin

Setup Istio by following the instructions in the Installation guide.
Deploy the Bookinfo sample application.
Review the Traffic Management concepts doc. Before attempting this task, you should be familiar with important terms such as destination rule, virtual service, and subset.

About this task

The Istio Bookinfo sample consists of four separate microservices, each with multiple versions. The initial goal of this task is to apply a rule that routes all traffic to v1 (version 1) of the ratings service. Later, you will apply a rule to route traffic based on the value of an HTTP request header.

To illustrate the problem this task solves, access the Bookinfo app's /productpage in a browser and refresh several times. You’ll notice that sometimes the book review output contains star ratings and other times it does not. This is because without an explicit default service version to route to, Istio routes requests to all available versions in a round robin fashion.

Apply a virtual service

To route to one version only, you apply virtual services that set the default version for the microservices. In this case, the virtual services will route all traffic to v1 of each microservice.

Run the following command to apply the virtual services:
```
$ kubectl apply -f @samples/bookinfo/networking/virtual-service-all-v1.yaml@
```
Because configuration propagation is eventually consistent, wait a few seconds for the virtual services to take effect.

Display the defined routes with the following command:

$ kubectl get virtualservices -o yaml
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: details
  ...
spec:
  hosts:
  - details
  http:
  - route:
    - destination:
        host: details
        subset: v1
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: productpage
  ...
spec:
  gateways:
  - bookinfo-gateway
  - mesh
  hosts:
  - productpage
  http:
  - route:
    - destination:
        host: productpage
        subset: v1
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings
  ...
spec:
  hosts:
  - ratings
  http:
  - route:
    - destination:
        host: ratings
        subset: v1
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews
  ...
spec:
  hosts:
  - reviews
  http:
  - route:
    - destination:
        host: reviews
        subset: v1
---

Display the corresponding subset definitions:
```
$ kubectl get destinationrules -o yaml
```

You have configured Istio to route to the v1 version of the Bookinfo microservices, including the ratings service.

Test the new routing configuration

You can easily test the new configuration by once again refreshing the /productpage of the Bookinfo app.

Open the Bookinfo site in your browser. The URL is http://$GATEWAY_URL/productpage, where $GATEWAY_URL is the External IP address of the ingress, as explained in the Bookinfo doc.
Notice that the reviews part of the page displays with no rating stars, no matter how many times you refresh. This is because you configured Istio to route all traffic for the reviews service to the version reviews:v1 and this version of the service does not access the star ratings service.

You have successfully accomplished the first part of this task: route traffic to one version of a service.

Route based on user identity

Next, you will change the route configuration so that all traffic from a specific user is routed to a specific service version. In this case, all traffic from a user named Jason will be routed to the service reviews:v2.

Note that Istio doesn't have any special, built-in understanding of user identity. This example is enabled by the fact that the productpage service adds a custom end-user header to all outbound HTTP requests to the reviews service.

Remember, reviews:v2 is the version that includes the star ratings feature.

Run the following command to enable user-based routing:

$ kubectl apply -f @samples/bookinfo/networking/virtual-service-reviews-test-v2.yaml@

Confirm the rule is created:

$ kubectl get virtualservice reviews -o yaml
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews
  ...
spec:
  hosts:
  - reviews
  http:
  - match:
    - headers:
        end-user:
          exact: jason
    route:
    - destination:
        host: reviews
        subset: v2
  - route:
    - destination:
        host: reviews
        subset: v1

On the /productpage of the Bookinfo app, log in as user jason.
Refresh the browser. What do you see? The star ratings appear next to each review.
Log in as another user (pick any name you wish).
Refresh the browser. Now the stars are gone. This is because traffic is routed to reviews:v1 for all users except Jason.

You have successfully configured Istio to route traffic based on user identity.

Understanding what happened

In this task, you used Istio to send 100% of the traffic to the v1 version of each of the Bookinfo services. You then set a rule to selectively send traffic to version v2 of the reviews service based on a custom end-user header added to the request by the productpage service.

Note that Kubernetes services, like the Bookinfo ones used in this task, must adhere to certain restrictions to take advantage of Istio's L7 routing features. Refer to the Requirements for Pods and Services for details.

In the traffic shifting task, you will follow the same basic pattern you learned here to configure route rules to gradually send traffic from one version of a service to another.

Cleanup

Remove the application virtual services:

$ kubectl delete -f @samples/bookinfo/networking/virtual-service-all-v1.yaml@

If you are not planning to explore any follow-on tasks, refer to the Bookinfo cleanup instructions to shutdown the application.