06-01 Feature toggling

The examples are based on the Istio setup guide.

After following the setup guide, to view the Bookinfo app webpage, run the following command and paste the output into your browser.

echo http://$GATEWAY_URL/productpage

During the set up process, you deployed services for details, reviews and ratings, and deployments for reviews v1, v2 & v3.

Run the following commands to see these:

kubectl get services

OUTPUT
NAME          TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)    AGE
details       ClusterIP   10.0.0.212      <none>        9080/TCP   29s
kubernetes    ClusterIP   10.0.0.1        <none>        443/TCP    25m
productpage   ClusterIP   10.0.0.57       <none>        9080/TCP   28s
ratings       ClusterIP   10.0.0.33       <none>        9080/TCP   29s
reviews       ClusterIP   10.0.0.28       <none>        9080/TCP   29s

kubectl get pods

OUTPUT
NAME                              READY   STATUS    RESTARTS   AGE
details-v1-78d78fbddf-tj56d       2/2     Running   1          20m30s
productpage-v1-85b9bf9cd7-zg7tr   1/2     Running   1          20m29s
ratings-v1-6c9dbf6b45-5djtx       2/2     Running   1          20m29s
reviews-v1-564b97f875-dzdt5       2/2     Running   1          20m30s
reviews-v2-568c7c9d8f-p5wrj       2/2     Running   1          20m29s
reviews-v3-67b4988599-7nhwz       2/2     Running   1          20m29s

• Istio uses the VirtualService component to handle traffic management.
• A VirtualService defines a set of traffic routing rules to apply when a host is addressed. If the traffic is matched, then it is sent to a named destination service (or subset/version of it) defined in the registry.
• Traffic can be routed based on:
  • A URI
  • Http Methods
  • Headers
  • Port
  • Queryparmas
• We will use a HTTPMatchRequest to illustrate how we can route to specific service versions based on a defined set of rules.

Exercise 1

The simple-routing.yaml file defines that all routes addressed to reviews will be directed to the version 1 subset:

kind: VirtualService
metadata:
  name: reviews
spec:
  hosts:
  - reviews
  http:
  - route:
    - destination:
        host: reviews
        subset: v1

Apply the file to route all traffic to version 1 of the reviews service:

kubectl apply -f exercise/simple-routing.yaml

Open the /productpage of the Bookinfo app in your browser. You will not see any stars next to the reviews as all traffic is routed to reviews:v1.

Kiali

Set up Kiali to easily visualise traffic routes.
Run

istioctl dashboard kiali

and login with the default username admin and default password admin.

• In the left navigation menu, select Graph and in the Namespace drop down, select default.

• The Kiali dashboard shows an overview of your mesh with the relationships between the services in the Bookinfo sample application. It also provides filters to visualize the traffic flow.

• In the second dropdown from the left that reads ‘No edge labels’, select ‘Requests percentage’.

• Reload the /productpage in the Bookinfo app a few times. Wait a few seconds and on the Kiali dashboard you will see that 100% of traffic is routed to reviews:v1.

Exercise 2

The rule-based-routing.yaml file uses a HTTPMatchRequest to specify the route based on the user.

The productpage service extracts user information from the session and uses it to construct a custom header, ‘end-user’. This header is then read by a match condition.

When a user logs in as jason, all routes addressed to reviews will be directed to version 2.
For everyone else, the routes addressed to reviews will be directed to version 1.

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

Apply the file to to route traffic based on the end user:

kubectl apply -f exercise/rule-based-routing.yaml

On the /productpage of the Bookinfo app, log in as user jason.

• Refresh the browser.
  The star ratings will appear next to each review. You are seeing reviews:v2.

Now log in as another user (pick any name).

• Refresh the browser.
  The star ratings are gone as traffic is routed to reviews:v1 for all users except jason.

Clean up

kubectl delete -f exercise/simple-routing.yaml
kubectl delete -f exercise/rule-based-routing.yaml