Knative Traffic Splitting

2020-01-08

Sample getting started tutorial on how to do traffic splitting with Knative Serving using Istio.

This is just my “hello world” application demonstrating stuff here:

While you can easily follow those tutorials, this article specifically designed to deconstruct the basic knative serving objects (Services, Congigurations, Routes, Revisions) and how to use them to split traffic.

images/object_model.png

Note: GCP Cloud RUn does not yet suport tags

We will be showing traffic splitting using

(A) Services

  • Deploy Service (v1)
    • Creates Revision istioinit-gke-0001
    • 100% traffic goes to istioinit-gke-0001
  • Create Revision istioinit-gke-0002
    • Update Service and split traffic between Revisions

(B) Confiuration and Routes

  • Deploy Configuration for (v1) and a Route to that Revision
    • Creates Revision istioinit-gke-0001
    • 100% traffic goes to istioinit-gke-0001
  • Create Configuration for (v2) and Revision istioinit-gke-0002
    • Update Route and split traffic between Revisions

The application i’ll be using is the handy one i used for various other tutorials that just returns the ‘version’ number (a simple 1 or 2 denoting the app verion that it hit). We will use the version number as the signal to confirm the routing scheme we intended to specify got applied.

You can find more info about the app istio_helloworld…the endpoint we’ll use is just /version.

Setup

  • Install Istio, Knative on GKE.

We will not be using GKE+Istio Addon or Cloud Run; the installation of Istio and Knative is done by hand as if its installed on k8s directly (Knative with any k8s)

Install GKE and Istio

gcloud container  clusters create cluster-1 --machine-type "n1-standard-2" --cluster-version=1.16.0 --zone us-central1-a  --num-nodes 4 --enable-ip-alias
gcloud container clusters get-credentials cluster-1 --zone us-central1-a

kubectl create clusterrolebinding cluster-admin-binding --clusterrole=cluster-admin --user=$(gcloud config get-value core/account)
kubectl create ns istio-system

export ISTIO_VERSION=1.3.2
wget https://github.com/istio/istio/releases/download/$ISTIO_VERSION/istio-$ISTIO_VERSION-linux.tar.gz
tar xvzf istio-$ISTIO_VERSION-linux.tar.gz

wget https://storage.googleapis.com/kubernetes-helm/helm-v2.11.0-linux-amd64.tar.gz
tar xf helm-v2.11.0-linux-amd64.tar.gz

export PATH=`pwd`/istio-$ISTIO_VERSION/bin:`pwd`/linux-amd64/:$PATH

helm template istio-$ISTIO_VERSION/install/kubernetes/helm/istio-init --name istio-init --namespace istio-system | kubectl apply -f -

helm template istio-$ISTIO_VERSION/install/kubernetes/helm/istio --name istio --namespace istio-system  \
   --set prometheus.enabled=true \
   --set sidecarInjectorWebhook.enabled=true > istio.yaml

kubectl apply -f istio.yaml
kubectl label namespace default istio-injection=enabled

At this point, you’ll have a GKE cluster with Istio running. You can verify everything is ok by running:

$ kubectl get no,po,rc,svc,ing,deployment -n istio-system

Acquire the GATEWAY_IP allocated to istio-ingress

$ export GATEWAY_IP=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
$ echo $GATEWAY_IP

Install Knative

We’ll instlal Knative on top of Istio now:

Follow the instructions detailed here Install on a Kubernetes cluster

A) Traffic Splitting with Services

First lets deploy a Service by itself.

$ kubectl apply -f service_1.yaml

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0001
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:1

This will automatically create a Configuration, Revision and a Route all for you:

$ kubectl get ksvc,configuration,routes,revisions
NAME                                        URL                                        LATESTCREATED        LATESTREADY          READY   REASON
service.serving.knative.dev/istioinit-gke   http://istioinit-gke.default.example.com   istioinit-gke-0001   istioinit-gke-0001   True    

NAME                                              LATESTCREATED        LATESTREADY          READY   REASON
configuration.serving.knative.dev/istioinit-gke   istioinit-gke-0001   istioinit-gke-0001   True    

NAME                                      URL                                        READY   REASON
route.serving.knative.dev/istioinit-gke   http://istioinit-gke.default.example.com   True    

NAME                                              CONFIG NAME     K8S SERVICE NAME     GENERATION   READY   REASON
revision.serving.knative.dev/istioinit-gke-0001   istioinit-gke   istioinit-gke-0001   1            True

We can now send it some traffic

$ for i in {1..1000}; do curl -s  -H "Host: istioinit-gke.default.example.com" http://${GATEWAY_IP}/version; sleep 1; done
11111111111

What the simple 1 there signifies is the version of the application we’ve deploy (which is version 1 since we deployed just gcr.io/mineral-minutia-820/istioinit:1).

A Service by itself needs to target traffic towards a revision…but so far we only have one revision. Lets deploy a revision for version 2 of our application. That is, a revision that has gcr.io/mineral-minutia-820/istioinit:2:

apiVersion: serving.knative.dev/v1
kind: Configuration
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0002
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:2
        imagePullPolicy: IfNotPresent

$ kubectl apply -f config_2.yaml

$ kubectl get ksvc,configuration,routes,revisions
NAME                                        URL                                        LATESTCREATED        LATESTREADY          READY   REASON
service.serving.knative.dev/istioinit-gke   http://istioinit-gke.default.example.com   istioinit-gke-0001   istioinit-gke-0001   True    

NAME                                              LATESTCREATED        LATESTREADY          READY   REASON
configuration.serving.knative.dev/istioinit-gke   istioinit-gke-0001   istioinit-gke-0001   True    

NAME                                      URL                                        READY   REASON
route.serving.knative.dev/istioinit-gke   http://istioinit-gke.default.example.com   True    

NAME                                              CONFIG NAME     K8S SERVICE NAME     GENERATION   READY     REASON
revision.serving.knative.dev/istioinit-gke-0001   istioinit-gke   istioinit-gke-0001   1            True      
revision.serving.knative.dev/istioinit-gke-0002   istioinit-gke   istioinit-gke-0002   2            True

We’ve got two revisions but the traffic for the Service is still going version 1.

To apply a 50/50 split on the Service itself, we need to add in the traffic section describing the targets

apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0002
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:2
  traffic:
  - revisionName: istioinit-gke-0001
    percent: 50
  - revisionName: istioinit-gke-0002
    percent: 50

Apply the config:

$ kubectl apply -f service_12.yaml

At this point, the frontend service traffic should be split evenly-ish:

$ for i in {1..1000}; do curl -s  -H "Host: istioinit-gke.default.example.com" http://${GATEWAY_IP}/version; sleep 1; done
1222122222212212221121112122111

Wonderful! we’ve used Services to split traffic. Lets rollback the config so we can use the Configuration and Revision directly:

kubectl delete -f config_2.yaml -f service_12.yaml

Verify:

$ kubectl get ksvc,configuration,routes,revisions
No resources found.

# you may have to wait a couple of mins for the pods to terminate; this is somthing up w/ the app i have

$ kubectl get po
No resources found.

Traffic Splitting with Configurations and Revisions

Now Deploy a config and route to that config for version 1:

cd config_revision/

$ kubectl apply -f config_1.yaml -f route_1.yaml

apiVersion: serving.knative.dev/v1
kind: Configuration
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0001
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:1
        imagePullPolicy: IfNotPresent
---
apiVersion: serving.knative.dev/v1
kind: Route
metadata:
  name: istioinit-gke
  namespace: default
spec:
  traffic:
  - revisionName: istioinit-gke-0001
    percent: 100

We didn’t deploy a service but an endpoite-route does get setup for you:

$ kubectl get ksvc,configuration,routes,revisions
NAME                                              LATESTCREATED        LATESTREADY          READY   REASON
configuration.serving.knative.dev/istioinit-gke   istioinit-gke-0001   istioinit-gke-0001   True    

NAME                                      URL                                        READY   REASON
route.serving.knative.dev/istioinit-gke   http://istioinit-gke.default.example.com   True    

NAME                                              CONFIG NAME     K8S SERVICE NAME     GENERATION   READY   REASON
revision.serving.knative.dev/istioinit-gke-0001   istioinit-gke   istioinit-gke-0001   1            True

Which means we can send traffic to it just as before:

$ for i in {1..1000}; do curl -s  -H "Host: istioinit-gke.default.example.com" http://${GATEWAY_IP}/version; sleep 1; done
11111111

Now deploy a configuration for version 2:

apiVersion: serving.knative.dev/v1
kind: Configuration
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0002
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:2
        imagePullPolicy: IfNotPresent

As before we’ve got a new revision but traffic still goes to 1

$ kubectl get ksvc,configuration,routes,revisions
NAME                                              LATESTCREATED        LATESTREADY          READY   REASON
configuration.serving.knative.dev/istioinit-gke   istioinit-gke-0002   istioinit-gke-0002   True    

NAME                                      URL                                        READY   REASON
route.serving.knative.dev/istioinit-gke   http://istioinit-gke.default.example.com   True    

NAME                                              CONFIG NAME     K8S SERVICE NAME     GENERATION   READY   REASON
revision.serving.knative.dev/istioinit-gke-0001   istioinit-gke   istioinit-gke-0001   1            True    
revision.serving.knative.dev/istioinit-gke-0002   istioinit-gke   istioinit-gke-0002   2            True

To split traffic, we’ll update the the route now to send 50/50 traffic split:

apiVersion: serving.knative.dev/v1
kind: Route
metadata:
  name: istioinit-gke
  namespace: default
spec:
  traffic:
  - revisionName: istioinit-gke-0001
    percent: 50
  - revisionName: istioinit-gke-0002
    percent: 50    
---

Then Verify:

$ for i in {1..1000}; do curl -s  -H "Host: istioinit-gke.default.example.com" http://${GATEWAY_IP}/version; sleep 1; done
2111111221222212222112

Thats it, this is a small snippet that shows traffic splitting w/ knative (well…atleast ast of 1/9/20).

You can find the yaml on this git repo here

good luck.

  • config_1.yaml
apiVersion: serving.knative.dev/v1
kind: Configuration
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0001
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:1
        imagePullPolicy: IfNotPresent
  • config_1.yaml
apiVersion: serving.knative.dev/v1
kind: Configuration
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0002
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:2
        imagePullPolicy: IfNotPresent
  • config2.yaml
apiVersion: serving.knative.dev/v1
kind: Configuration
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0002
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:2
        imagePullPolicy: IfNotPresent
  • service1.yaml
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0001
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:1
  • service12.yaml
apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: istioinit-gke
  namespace: default
spec:
  template:
    metadata:
      name: istioinit-gke-0001
    spec:
      containers:
      - image: gcr.io/mineral-minutia-820/istioinit:1
  traffic:
  - revisionName: istioinit-gke-0001
    percent: 50
  - revisionName: istioinit-gke-0002
    percent: 50

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