istio.io/_docs/tasks/request-routing.md

title	overview	order	layout	type
Configuring Request Routing	This task shows you how to configure dynamic request routing based on weights and HTTP headers.	50	docs	markdown

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This task shows you how to configure dynamic request routing based on weights and HTTP headers.

Before you begin

• Setup Istio by following the instructions in the Installation guide.

• Deploy the BookInfo sample application.

Content-based routing

Because the BookInfo sample deploys 3 versions of the reviews microservice, we need to set a default route. Otherwise if you access the application several times, you would notice that sometimes the output contains star ratings. This is because without an explicit default version set, Istio will route requests to all available versions of a service in a random fashion.

1. Set the default version for all microservices to v1.

   istioctl create -f samples/apps/bookinfo/route-rule-all-v1.yaml
   

   You can display the routes that are defined with the following command:

   istioctl get route-rules -o yaml
   

   type: route-rule
   name: ratings-default
   namespace: default
   spec:
     destination: ratings.default.svc.cluster.local
     precedence: 1
     route:
     - tags:
         version: v1
       weight: 100
   ---
   type: route-rule
   name: reviews-default
   namespace: default
   spec:
     destination: reviews.default.svc.cluster.local
     precedence: 1
     route:
     - tags:
         version: v1
       weight: 100
   ---
   type: route-rule
   name: details-default
   namespace: default
   spec:
     destination: details.default.svc.cluster.local
     precedence: 1
     route:
     - tags:
         version: v1
       weight: 100
   ---
   type: route-rule
   name: productpage-default
   namespace: default
   spec:
     destination: productpage.default.svc.cluster.local
     precedence: 1
     route:
     - tags:
         version: v1
       weight: 100
   ---
   

   Since rule propagation to the proxies is asynchronous, you should wait a few seconds for the rules to propagate to all pods before attempting to access the application.

2. Open the BookInfo URL (http://$GATEWAY_URL/productpage) in your browser

   You should see the BookInfo application productpage displayed. Notice that the productpage is displayed with no rating stars since reviews:v1 does not access the ratings service.

3. Route a specific user to reviews:v2

   Lets enable the ratings service for test user "jason" by routing productpage traffic to reviews:v2 instances.

   istioctl create -f samples/apps/bookinfo/route-rule-reviews-test-v2.yaml
   

   Confirm the rule is created:

   istioctl get route-rule reviews-test-v2
   

   destination: reviews.default.svc.cluster.local
   match:
     httpHeaders:
       cookie:
         regex: ^(.*?;)?(user=jason)(;.*)?$
   precedence: 2
   route:
   - tags:
       version: v2
   

4. Log in as user "jason" at the productpage web page.

   You should now see ratings (1-5 stars) next to each review. Notice that if you log in as any other user, you will continue to see reviews:v1.

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 a header (i.e., a user cookie) in a request.

Once the v2 version has been tested to our satisfaction, we could use Istio to send traffic from all users to v2, optionally in a gradual fashion by using a sequence of rules with weights less than 100 to migrate traffic in steps, for example 10, 20, 30, ... 100%.

If you now proceed to the fault injection task, you will see that with simple testing, the v2 version of the reviews service has a bug, which is fixed in v3. So after exploring that task, you can route all user traffic from reviews:v1 to reviews:v3 in two steps as follows:

1. First, transfer 50% of traffic from reviews:v1 to reviews:v3 with the following command:

   istioctl replace -f samples/apps/bookinfo/route-rule-reviews-50-v3.yaml
   

   Notice that we are using istioctl replace instead of create.

2. To see the new version you need to either Log out as test user "jason" or delete the test rules that we created exclusively for him:

   istioctl delete route-rule reviews-test-v2
   istioctl delete route-rule ratings-test-delay
   

   You should now see red colored star ratings approximately 50% of the time when you refresh the productpage.

   Note: With the Envoy sidecar implementation, you may need to refresh the productpage multiple times to see the proper distribution. You can modify the rules to route 90% of the traffic to v3 to see red stars more often.

3. When version v3 of the reviews microservice is stable, route 100% of the traffic to reviews:v3:

   istioctl replace -f samples/apps/bookinfo/route-rule-reviews-v3.yaml
   

   You can now log in to the productpage as any user and you should always see book reviews with red colored star ratings for each review.

What's next

• Learn more about request routing.

• Test the BookInfo application resiliency by injecting faults.