TCP Traffic Shifting

This task shows you how to shift TCP traffic from one version of a microservice to another.

A common use case is to migrate TCP traffic gradually from an older version of a microservice to a new one. In Istio, you accomplish this goal by configuring a sequence of routing rules that redirect a percentage of TCP traffic from one destination to another.

In this task, you will send 100% of the TCP traffic to tcp-echo:v1. Then, you will route 20% of the TCP traffic to tcp-echo:v2 using Istio’s weighted routing feature.

Before you begin

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

• Review the Traffic Management concepts doc.

Set up the test environment

1. To get started, create a namespace for testing TCP traffic shifting.

   $ kubectl create namespace istio-io-tcp-traffic-shifting

2. Deploy the curl sample app to use as a test source for sending requests.

   Zip

   $ kubectl apply -f @samples/curl/curl.yaml@ -n istio-io-tcp-traffic-shifting

3. Deploy the v1 and v2 versions of the tcp-echo microservice.

   Zip

   $ kubectl apply -f @samples/tcp-echo/tcp-echo-services.yaml@ -n istio-io-tcp-traffic-shifting

Apply weight-based TCP routing

1. Route all TCP traffic to the v1 version of the tcp-echo microservice.

$ kubectl apply -f @samples/tcp-echo/tcp-echo-all-v1.yaml@ -n istio-io-tcp-traffic-shifting

$ kubectl apply -f @samples/tcp-echo/gateway-api/tcp-echo-all-v1.yaml@ -n istio-io-tcp-traffic-shifting

2. Determine the ingress IP and port:

$ kubectl wait --for=condition=programmed gtw tcp-echo-gateway -n istio-io-tcp-traffic-shifting $ export INGRESS_HOST=$(kubectl get gtw tcp-echo-gateway -n istio-io-tcp-traffic-shifting -o jsonpath='{.status.addresses[0].value}') $ export TCP_INGRESS_PORT=$(kubectl get gtw tcp-echo-gateway -n istio-io-tcp-traffic-shifting -o jsonpath='{.spec.listeners[?(@.name=="tcp-31400")].port}')

3. Confirm that the tcp-echo service is up and running by sending some TCP traffic.

   $ export CURL=$(kubectl get pod -l app=curl -n istio-io-tcp-traffic-shifting -o jsonpath={.items..metadata.name}) $ for i in {1..20}; do \ kubectl exec "$CURL" -c curl -n istio-io-tcp-traffic-shifting -- sh -c "(date; sleep 1) | nc $INGRESS_HOST $TCP_INGRESS_PORT"; \ done one Mon Nov 12 23:24:57 UTC 2022 one Mon Nov 12 23:25:00 UTC 2022 one Mon Nov 12 23:25:02 UTC 2022 one Mon Nov 12 23:25:05 UTC 2022 one Mon Nov 12 23:25:07 UTC 2022 one Mon Nov 12 23:25:10 UTC 2022 one Mon Nov 12 23:25:12 UTC 2022 one Mon Nov 12 23:25:15 UTC 2022 one Mon Nov 12 23:25:17 UTC 2022 one Mon Nov 12 23:25:19 UTC 2022 ...

   You should notice that all the timestamps have a prefix of one, which means that all traffic was routed to the v1 version of the tcp-echo service.

4. Transfer 20% of the traffic from tcp-echo:v1 to tcp-echo:v2 with the following command:

$ kubectl apply -f @samples/tcp-echo/tcp-echo-20-v2.yaml@ -n istio-io-tcp-traffic-shifting

$ kubectl apply -f @samples/tcp-echo/gateway-api/tcp-echo-20-v2.yaml@ -n istio-io-tcp-traffic-shifting

5. Wait a few seconds for the new rules to propagate and then confirm that the rule was replaced:

$ kubectl get virtualservice tcp-echo -o yaml -n istio-io-tcp-traffic-shifting apiVersion: networking.istio.io/v1 kind: VirtualService ... spec: ... tcp: - match: - port: 31400 route: - destination: host: tcp-echo port: number: 9000 subset: v1 weight: 80 - destination: host: tcp-echo port: number: 9000 subset: v2 weight: 20

$ kubectl get tcproute tcp-echo -o yaml -n istio-io-tcp-traffic-shifting apiVersion: gateway.networking.k8s.io/v1alpha2 kind: TCPRoute ... spec: parentRefs: - group: gateway.networking.k8s.io kind: Gateway name: tcp-echo-gateway sectionName: tcp-31400 rules: - backendRefs: - group: "" kind: Service name: tcp-echo-v1 port: 9000 weight: 80 - group: "" kind: Service name: tcp-echo-v2 port: 9000 weight: 20 ...

6. Send some more TCP traffic to the tcp-echo microservice.

   $ export CURL=$(kubectl get pod -l app=curl -n istio-io-tcp-traffic-shifting -o jsonpath={.items..metadata.name}) $ for i in {1..20}; do \ kubectl exec "$CURL" -c curl -n istio-io-tcp-traffic-shifting -- sh -c "(date; sleep 1) | nc $INGRESS_HOST $TCP_INGRESS_PORT"; \ done one Mon Nov 12 23:38:45 UTC 2022 two Mon Nov 12 23:38:47 UTC 2022 one Mon Nov 12 23:38:50 UTC 2022 one Mon Nov 12 23:38:52 UTC 2022 one Mon Nov 12 23:38:55 UTC 2022 two Mon Nov 12 23:38:57 UTC 2022 one Mon Nov 12 23:39:00 UTC 2022 one Mon Nov 12 23:39:02 UTC 2022 one Mon Nov 12 23:39:05 UTC 2022 one Mon Nov 12 23:39:07 UTC 2022 ...

   You should now notice that about 20% of the timestamps have a prefix of two, which means that 80% of the TCP traffic was routed to the v1 version of the tcp-echo service, while 20% was routed to v2.

Understanding what happened

In this task you partially migrated TCP traffic from an old to new version of the tcp-echo service using Istio’s weighted routing feature. Note that this is very different than doing version migration using the deployment features of container orchestration platforms, which use instance scaling to manage the traffic.

With Istio, you can allow the two versions of the tcp-echo service to scale up and down independently, without affecting the traffic distribution between them.

For more information about version routing with autoscaling, check out the blog article Canary Deployments using Istio.

Cleanup

1. Remove the routing rules:

$ kubectl delete -f @samples/tcp-echo/tcp-echo-all-v1.yaml@ -n istio-io-tcp-traffic-shifting

$ kubectl delete -f @samples/tcp-echo/gateway-api/tcp-echo-all-v1.yaml@ -n istio-io-tcp-traffic-shifting

2. Remove the curl sample, tcp-echo application and test namespace:

   ZipZip

   $ kubectl delete -f @samples/curl/curl.yaml@ -n istio-io-tcp-traffic-shifting $ kubectl delete -f @samples/tcp-echo/tcp-echo-services.yaml@ -n istio-io-tcp-traffic-shifting $ kubectl delete namespace istio-io-tcp-traffic-shifting