Advanced Route Rules

Traffic Steering

OpenTracing, the tracing tool that Istio uses, adds the user-agent header to its baggage in the Customer service. A baggage is a set of key:value pairs that cross service-boundaries to carry some data that will be available throughout the trace.

From Customer, the baggage is automatically propagated to all downstream services. To enable automatic baggage propagation all intermediate services must to be instrumented with OpenTracing.

The baggage header for user agent has following form baggage-user-agent: <value>.

Set recommendation:v1 and recommendation:v2 as subsets.

kubectl apply -f manifests/istio/routing-simple/recommendation-destination-rule-v1-v2.yml

Set Safari users to v2.

k8s istio 5 traffic steering

kubectl apply -f manifests/istio/routing-advanced/canary-deployment/recommendation-v2-safari-virtual-service.yml

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: recommendation
spec:
  hosts:
  - recommendation
  http:
  - route:
    match:
    - headers:
        baggage-user-agent:
          regex: .*Safari.*
    - destination:
        host: recommendation
        subset: version-v2
  - route:
    - destination:
        host: recommendation
        subset: version-v1

Test with a Safari (or even Chrome on Mac since it includes Safari in the string). Safari only sees v2 responses from recommendation

Test with a Firefox browser, it should only see v1 responses from recommendation.

Alternatively, you can also attempt to use the curl -A command to test with different user-agent strings.

curl -A Safari $customer
curl -A Firefox $customer

You can describe the virtualservice to see its configuration

kubectl get virtualservice -o yaml

Clean up

kubectl delete destinationrule recommendation
kubectl delete virtualservice recommendation

Load Balancer

By default, you will see "round-robin" style load-balancing, but you can change it up, with the RANDOM option being fairly visible to the naked eye.

Add another v2 pod to the mix

kubectl scale deployment recommendation-v2 --replicas=2

Wait a bit and curl the customer endpoint many times

curl $customer

Add a 3rd v2 pod to the mix

kubectl scale deployment recommendation-v2 --replicas=3

NAME                                  READY     STATUS    RESTARTS   AGE
customer-1755156816-cjd2z             2/2       Running   0          1h
preference-3336288630-2cc6f           2/2       Running   0          1h
recommendation-v1-3719512284-bn42p    2/2       Running   0          59m
recommendation-v2-2815683430-97nnf    2/2       Running   0          43m
recommendation-v2-2815683430-d49n6    2/2       Running   0          51m
recommendation-v2-2815683430-tptf2    2/2       Running   0          33m

Wait for those 2/2 (two containers in each pod) and then poll the customer endpoint:

while true; do curl $customer; sleep .5; done

The results should follow a fairly normal round-robin distribution pattern

customer => preference => recommendation v1 from '99634814-d2z2t': 1145
customer => preference => recommendation v2 from '2819441432-525lh': 1
customer => preference => recommendation v2 from '2819441432-rg45q': 2
customer => preference => recommendation v2 from '2819441432-bs5ck': 181
customer => preference => recommendation v1 from '99634814-d2z2t': 1146
customer => preference => recommendation v2 from '2819441432-rg45q': 3
customer => preference => recommendation v2 from '2819441432-rg45q': 4
customer => preference => recommendation v2 from '2819441432-bs5ck': 182

Now, add the Random LB DestinationPolicy

kubectl apply -f manifests/istio/routing-advanced/load-balancer/recommendation-destination-rule-lb_policy_random.yml

kind: DestinationRule
metadata:
  name: recommendation
spec:
  host: recommendation
  trafficPolicy:
    loadBalancer:
      simple: RANDOM

And you should see a different pattern of which pod is being selected

k8s istio 5 randome lb

customer => preference => recommendation v2 from '2819441432-rg45q': 10
customer => preference => recommendation v2 from '2819441432-525lh': 3
customer => preference => recommendation v2 from '2819441432-rg45q': 11
customer => preference => recommendation v1 from '99634814-d2z2t': 1153
customer => preference => recommendation v1 from '99634814-d2z2t': 1154
customer => preference => recommendation v1 from '99634814-d2z2t': 1155
customer => preference => recommendation v2 from '2819441432-rg45q': 12
customer => preference => recommendation v2 from '2819441432-525lh': 4
customer => preference => recommendation v2 from '2819441432-525lh': 5
customer => preference => recommendation v2 from '2819441432-rg45q': 13
customer => preference => recommendation v2 from '2819441432-rg45q': 14

Clean up

kubectl delete -f manifests/istio/routing-advanced/load-balancer/recommendation-destination-rule-lb_policy_random.yml

kubectl scale deployment recommendation-v2 --replicas=1

Next >