---
title: Request Routing
description: This task shows you how to configure dynamic request routing to multiple versions of a microservice.
weight: 10
aliases:
    - /docs/tasks/request-routing.html
keywords: [traffic-management,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](/docs/setup/).

* Deploy the [Bookinfo](/docs/examples/bookinfo/) sample application.

* Review the [Traffic Management](/docs/concepts/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](/docs/examples/bookinfo/) sample consists of four separate microservices, each with multiple versions.
Three different versions of one of the microservices, `reviews`, have been deployed and are running concurrently.
To illustrate the problem this causes, 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.

The initial goal of this task is to apply rules that route all traffic to `v1` (version 1) of the microservices. Later, you
will apply a rule to route traffic based on the value of an HTTP request header.

## 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.

{{< warning >}}
If you haven't already applied destination rules, follow the instructions in [Apply Default Destination Rules](/docs/examples/bookinfo/#apply-default-destination-rules).
{{< /warning >}}

1.  Run the following command to apply the virtual services:

    {{< text bash >}}
    $ kubectl apply -f @samples/bookinfo/networking/virtual-service-all-v1.yaml@
    {{< /text >}}

    Because configuration propagation is eventually consistent, wait a few seconds
    for the virtual services to take effect.

1. Display the defined routes with the following command:

    {{< text bash yaml >}}
    $ 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
    ---
    {{< /text >}}

1. You can also display the corresponding `subset` definitions with the following command:

    {{< text bash >}}
    $ kubectl get destinationrules -o yaml
    {{< /text >}}

You have configured Istio to route to the `v1` version of the Bookinfo microservices,
most importantly the `reviews` service version 1.

## Test the new routing configuration

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

1.  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](/docs/examples/bookinfo/#determine-the-ingress-ip-and-port) 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.

1. Run the following command to enable user-based routing:

    {{< text bash >}}
    $ kubectl apply -f @samples/bookinfo/networking/virtual-service-reviews-test-v2.yaml@
    {{< /text >}}

1. Confirm the rule is created:

    {{< text bash yaml >}}
    $ 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
    {{< /text >}}

1.  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.

1. 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](/docs/ops/deployment/requirements/) for details.

In the [traffic shifting](/docs/tasks/traffic-management/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

1. Remove the application virtual services:

    {{< text bash >}}
    $ kubectl delete -f @samples/bookinfo/networking/virtual-service-all-v1.yaml@
    {{< /text >}}

1. If you are not planning to explore any follow-on tasks, refer to the
  [Bookinfo cleanup](/docs/examples/bookinfo/#cleanup) instructions
  to shutdown the application.
