Configure Traffic Split

Balance traffic between services with the SMI Traffic Split API

We will now demonstrate how to balance traffic between two Kubernetes services, commonly known as a traffic split. We will be splitting the traffic directed to the root bookstore service between the backends bookstore-v1 service and bookstore-v2 service. The bookstore-v1 and bookstore-v2 services are also known as leaf services. Learn more on how to configure services for Traffic Splitting in the traffic Splitting how-to guide

Deploy bookstore v2 application

To demonstrate usage of SMI traffic access and split policies, we will now deploy version v2 of the bookstore application (bookstore-v2) - remember that if you are using openshift, you must add the security context constraint to the bookstore-v2 service account.

# Contains the bookstore-v2 Kubernetes Service, Service Account, Deployment and SMI Traffic Target resource to allow
# `bookbuyer` to communicate with `bookstore-v2` pods
kubectl apply -f https://raw.githubusercontent.com/flomesh-io/fsm-docs/release/v1.2/manifests/apps/bookstore-v2.yaml

Wait for the bookstore-v2 pod to be running in the bookstore namespace. Next, exit and restart the port-forward scripts in order to access v2 of bookstore:

bash <<EOF
./scripts/port-forward-bookbuyer-ui.sh &
./scripts/port-forward-bookstore-ui.sh app=bookstore,version=v1 &
./scripts/port-forward-bookstore-ui-v2.sh &
./scripts/port-forward-bookthief-ui.sh &
wait
EOF

The bookstore-v2 counter should be incrementing because traffic to the root bookstore service is configured with a label selector which selects endpoints that include both the bookstore-v1 and bookstore-v2 backend pods.

Create SMI Traffic Split

Deploy the SMI traffic split policy to direct 100 percent of the traffic sent to the root bookstore service to the bookstore-v1 service backend. This is necessary to ensure traffic directed to the bookstore service is only directed to version v1 of the bookstore app, which includes the pods backing the bookstore-v1 service. The TrafficSplit configuration will be subsequently updated to direct a percentage of traffic to version v2 of the bookstore service using the bookstore-v2 leaf service.

For this reason, it is important to ensure client applications always communicate with the root service if a traffic split is desired. Otherwise the client application will need to be updated to communicate with the root service when a traffic split is desired.

kubectl apply -f https://raw.githubusercontent.com/flomesh-io/fsm-docs/release/v1.2/manifests/split/traffic-split-v1.yaml

Note: The root service is a Kubernetes service whose selector needs to match the pods backing the leaf services. In this demo, the root service bookstore has the selector app:bookstore, which matches both the labels app:bookstore,version:v1 and app:bookstore,version=v2 on the bookstore (v1) and bookstore-v2 deployments respectively. The root service can be referred to in the SMI Traffic Split resource as the name of the service with or without the .<namespace>.svc.cluster.local suffix.

The count for the books sold from the bookstore-v2 browser window should stop incrementing. This is because the current traffic split policy is weighted 100 for bookstore-v1 which exludes pods backing the bookstore-v2 service. You can verify the traffic split policy by running the following and viewing the Backends properties:

kubectl describe trafficsplit bookstore-split -n bookstore

Split Traffic to Bookstore v2

Update the SMI Traffic Split policy to direct 50 percent of the traffic sent to the root bookstore service to the bookstore service and 50 perfect to bookstore-v2 service by adding the bookstore-v2 backend to the spec and modifying the weight fields.

kubectl apply -f https://raw.githubusercontent.com/flomesh-io/fsm-docs/release/v1.2/manifests/split/traffic-split-50-50.yaml

Wait for the changes to propagate and observe the counters increment for bookstore and bookstore-v2 in your browser windows. Both

counters should be incrementing:

Split All Traffic to Bookstore v2

Update the bookstore-split TrafficSplit to configure all traffic to go to bookstore-v2:

kubectl apply -f https://raw.githubusercontent.com/flomesh-io/fsm-docs/release/v1.2/manifests/split/traffic-split-v2.yaml

Wait for the changes to propagate and observe the counters increment for bookstore-v2 and freeze for bookstore in your

browser windows:

Now, all traffic directed to the bookstore service is flowing to bookstore-v2.

Next Steps

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Last modified June 18, 2024: fix workflow issue (c83135d)