TCP Traffic Shifting

4 minute read

This task shows you how to gradually migrate TCP traffic from one version of a microservice to another. For example, you might migrate TCP traffic from an older version to a new version.

A common use case is to migrate TCP traffic gradually from one version of a microservice to another. In Istio, you accomplish this goal by configuring a sequence of rules that route a percentage of TCP traffic to one service or 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.

Apply weight-based TCP routing

To get started, deploy the v1 version of the tcp-echo microservice.
- First, create a namespace for testing TCP traffic shifting
```
$ kubectl create namespace istio-io-tcp-traffic-shifting
```
- If you are using manual sidecar injection, use the following command
  Zip
```
$ kubectl apply -f <(istioctl kube-inject -f @samples/tcp-echo/tcp-echo-services.yaml@) -n istio-io-tcp-traffic-shifting
```
  The istioctl kube-inject command is used to manually modify the tcp-echo-services.yaml file before creating the deployments.
- If you are using a cluster with automatic sidecar injection enabled, label the istio-io-tcp-traffic-shifting namespace with istio-injection=enabled
```
$ kubectl label namespace istio-io-tcp-traffic-shifting istio-injection=enabled
```
  Then simply deploy the services using kubectl
  Zip
```
$ kubectl apply -f @samples/tcp-echo/tcp-echo-services.yaml@ -n istio-io-tcp-traffic-shifting
```

Next, 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

Confirm that the tcp-echo service is up and running.

The $INGRESS_HOST variable below is the External IP address of the ingress, as explained in the Ingress Gateways doc. To obtain the $INGRESS_PORT value, use the following command.

$ export INGRESS_PORT=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="tcp")].port}')

Send some TCP traffic to the tcp-echo microservice.

$ for i in {1..10}; do \
docker run -e INGRESS_HOST=$INGRESS_HOST -e INGRESS_PORT=$INGRESS_PORT -it --rm busybox sh -c "(date; sleep 1) | nc $INGRESS_HOST $INGRESS_PORT"; \
done
one Mon Nov 12 23:24:57 UTC 2018
one Mon Nov 12 23:25:00 UTC 2018
one Mon Nov 12 23:25:02 UTC 2018
one Mon Nov 12 23:25:05 UTC 2018
one Mon Nov 12 23:25:07 UTC 2018
one Mon Nov 12 23:25:10 UTC 2018
one Mon Nov 12 23:25:12 UTC 2018
one Mon Nov 12 23:25:15 UTC 2018
one Mon Nov 12 23:25:17 UTC 2018
one Mon Nov 12 23:25:19 UTC 2018

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.

Transfer 20% of the traffic from tcp-echo:v1 to tcp-echo:v2 with the following command:
Zip
```
$ kubectl apply -f @samples/tcp-echo/tcp-echo-20-v2.yaml@ -n istio-io-tcp-traffic-shifting
```
Wait a few seconds for the new rules to propagate.

Confirm that the rule was replaced:

$ kubectl get virtualservice tcp-echo -o yaml -n istio-io-tcp-traffic-shifting
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: tcp-echo
  ...
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

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

$ for i in {1..10}; do \
docker run -e INGRESS_HOST=$INGRESS_HOST -e INGRESS_PORT=$INGRESS_PORT -it --rm busybox sh -c "(date; sleep 1) | nc $INGRESS_HOST $INGRESS_PORT"; \
done
one Mon Nov 12 23:38:45 UTC 2018
two Mon Nov 12 23:38:47 UTC 2018
one Mon Nov 12 23:38:50 UTC 2018
one Mon Nov 12 23:38:52 UTC 2018
one Mon Nov 12 23:38:55 UTC 2018
two Mon Nov 12 23:38:57 UTC 2018
one Mon Nov 12 23:39:00 UTC 2018
one Mon Nov 12 23:39:02 UTC 2018
one Mon Nov 12 23:39:05 UTC 2018
one Mon Nov 12 23:39:07 UTC 2018

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

Remove the tcp-echo application and 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/tcp-echo-services.yaml@ -n istio-io-tcp-traffic-shifting
$ kubectl delete namespace istio-io-tcp-traffic-shifting