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Istio A/B Testing
This guide shows you how to automate A/B testing with Istio and Flagger.
Besides weighted routing, Flagger can be configured to route traffic to the canary based on HTTP match conditions. In an A/B testing scenario, you'll be using HTTP headers or cookies to target a certain segment of your users. This is particularly useful for frontend applications that require session affinity.
Flagger A/B Testing Stages
Prerequisites
Flagger requires a Kubernetes cluster v1.16 or newer and Istio v1.0 or newer.
Install Istio with telemetry support and Prometheus:
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istioctl manifest install --set profile=default
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​
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kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.8/samples/addons/prometheus.yaml
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Install Flagger in the
istio-system namespace:1
kubectl apply -k github.com/fluxcd/flagger//kustomize/istio
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Create an ingress gateway to expose the demo app outside of the mesh:
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apiVersion: networking.istio.io/v1alpha3
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kind: Gateway
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metadata:
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name: public-gateway
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namespace: istio-system
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spec:
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selector:
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istio: ingressgateway
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servers:
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- port:
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number: 80
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name: http
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protocol: HTTP
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hosts:
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- "*"
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Bootstrap
Create a test namespace with Istio sidecar injection enabled:
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kubectl create ns test
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kubectl label namespace test istio-injection=enabled
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Create a deployment and a horizontal pod autoscaler:
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kubectl apply -k https://github.com/fluxcd/flagger//kustomize/podinfo?ref=main
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Deploy the load testing service to generate traffic during the canary analysis:
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kubectl apply -k https://github.com/fluxcd/flagger//kustomize/tester?ref=main
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Create a canary custom resource (replace example.com with your own domain):
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apiVersion: flagger.app/v1beta1
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kind: Canary
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metadata:
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name: podinfo
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namespace: test
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spec:
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# deployment reference
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targetRef:
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apiVersion: apps/v1
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kind: Deployment
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name: podinfo
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# the maximum time in seconds for the canary deployment
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# to make progress before it is rollback (default 600s)
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progressDeadlineSeconds: 60
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# HPA reference (optional)
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autoscalerRef:
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apiVersion: autoscaling/v2beta2
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kind: HorizontalPodAutoscaler
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name: podinfo
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service:
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# container port
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port: 9898
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# Istio gateways (optional)
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gateways:
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- public-gateway.istio-system.svc.cluster.local
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# Istio virtual service host names (optional)
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hosts:
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- app.example.com
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# Istio traffic policy (optional)
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trafficPolicy:
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tls:
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# use ISTIO_MUTUAL when mTLS is enabled
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mode: DISABLE
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analysis:
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# schedule interval (default 60s)
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interval: 1m
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# total number of iterations
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iterations: 10
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# max number of failed iterations before rollback
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threshold: 2
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# canary match condition
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match:
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- headers:
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user-agent:
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regex: ".*Firefox.*"
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- headers:
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cookie:
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regex: "^(.*?;)?(type=insider)(;.*)?quot;
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metrics:
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- name: request-success-rate
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# minimum req success rate (non 5xx responses)
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# percentage (0-100)
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thresholdRange:
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min: 99
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interval: 1m
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- name: request-duration
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# maximum req duration P99
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# milliseconds
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thresholdRange:
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max: 500
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interval: 30s
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# generate traffic during analysis
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webhooks:
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- name: load-test
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url: http://flagger-loadtester.test/
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timeout: 15s
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metadata:
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cmd: "hey -z 1m -q 10 -c 2 -H 'Cookie: type=insider' http://podinfo.test:9898/"
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The above configuration will run an analysis for ten minutes targeting Firefox users and those that have an insider cookie.
Save the above resource as podinfo-abtest.yaml and then apply it:
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kubectl apply -f ./podinfo-abtest.yaml
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After a couple of seconds Flagger will create the canary objects:
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# applied
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deployment.apps/podinfo
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horizontalpodautoscaler.autoscaling/podinfo
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canary.flagger.app/podinfo
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​
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# generated
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deployment.apps/podinfo-primary
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horizontalpodautoscaler.autoscaling/podinfo-primary
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service/podinfo
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service/podinfo-canary
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service/podinfo-primary
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destinationrule.networking.istio.io/podinfo-canary
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destinationrule.networking.istio.io/podinfo-primary
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virtualservice.networking.istio.io/podinfo
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Automated canary promotion
Trigger a canary deployment by updating the container image:
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kubectl -n test set image deployment/podinfo \
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podinfod=ghcr.io/stefanprodan/podinfo:6.0.1
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Flagger detects that the deployment revision changed and starts a new rollout:
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kubectl -n test describe canary/abtest
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​
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Status:
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Failed Checks: 0
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Phase: Succeeded
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Normal Synced 3m flagger New revision detected podinfo.test
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Normal Synced 3m flagger Scaling up podinfo.test
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Warning Synced 3m flagger Waiting for podinfo.test rollout to finish: 0 of 1 updated replicas are available
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Normal Synced 3m flagger Advance podinfo.test canary iteration 1/10
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Normal Synced 3m flagger Advance podinfo.test canary iteration 2/10
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Normal Synced 3m flagger Advance podinfo.test canary iteration 3/10
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Normal Synced 2m flagger Advance podinfo.test canary iteration 4/10
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Normal Synced 2m flagger Advance podinfo.test canary iteration 5/10
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Normal Synced 1m flagger Advance podinfo.test canary iteration 6/10
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Normal Synced 1m flagger Advance podinfo.test canary iteration 7/10
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Normal Synced 55s flagger Advance podinfo.test canary iteration 8/10
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Normal Synced 45s flagger Advance podinfo.test canary iteration 9/10
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Normal Synced 35s flagger Advance podinfo.test canary iteration 10/10
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Normal Synced 25s flagger Copying podinfo.test template spec to podinfo-primary.test
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Warning Synced 15s flagger Waiting for podinfo-primary.test rollout to finish: 1 of 2 updated replicas are available
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Normal Synced 5s flagger Promotion completed! Scaling down podinfo.test
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Note that if you apply new changes to the deployment during the canary analysis, Flagger will restart the analysis.
You can monitor all canaries with:
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watch kubectl get canaries --all-namespaces
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​
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NAMESPACE NAME STATUS WEIGHT LASTTRANSITIONTIME
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test podinfo Progressing 100 2019-03-16T14:05:07Z
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prod frontend Succeeded 0 2019-03-15T16:15:07Z
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prod backend Failed 0 2019-03-14T17:05:07Z
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Automated rollback
During the canary analysis you can generate HTTP 500 errors and high latency to test Flagger's rollback.
Generate HTTP 500 errors:
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watch curl -b 'type=insider' http://app.example.com/status/500
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Generate latency:
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watch curl -b 'type=insider' http://app.example.com/delay/1
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When the number of failed checks reaches the canary analysis threshold, the traffic is routed back to the primary, the canary is scaled to zero and the rollout is marked as failed.
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kubectl -n test describe canary/podinfo
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Status:
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Failed Checks: 2
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Phase: Failed
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Events:
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Type Reason Age From Message
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---- ------ ---- ---- -------
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Normal Synced 3m flagger Starting canary deployment for podinfo.test
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Normal Synced 3m flagger Advance podinfo.test canary iteration 1/10
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Normal Synced 3m flagger Advance podinfo.test canary iteration 2/10
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Normal Synced 3m flagger Advance podinfo.test canary iteration 3/10
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Normal Synced 3m flagger Halt podinfo.test advancement success rate 69.17% < 99%
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Normal Synced 2m flagger Halt podinfo.test advancement success rate 61.39% < 99%
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Warning Synced 2m flagger Rolling back podinfo.test failed checks threshold reached 2
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Warning Synced 1m flagger Canary failed! Scaling down podinfo.test
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The above procedure can be extended with custom metrics checks, webhooks, manual promotion approval and Slack or MS Teams notifications.
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