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Hybrid (A/B + SLOs) testing

Scenario: Hybrid (A/B + SLOs) testing and progressive rollout of Knative services

Hybrid (A/B + SLOs) testing enables you to combine A/B or A/B/n testing with a reward metric on the one hand with SLO validation using objectives on the other. Among the versions that satisfy objectives, the version which performs best in terms of the reward metric is the winner. In this tutorial, you will:

  1. Perform hybrid (A/B + SLOs) testing.
  2. Specify user-engagement as the reward metric.
  3. Specify latency and error-rate based objectives; these metrics will be collected using Iter8's built-in metrics collection feature.
  4. Combine hybrid (A/B + SLOs) testing with progressive rollout. Iter8 will progressively shift traffic towards the winner and promote it at the end as depicted below.

Hybrid testing

Platform setup

Follow these steps to install Iter8 and Knative in your K8s cluster.

1. Create app versions

Deploy two versions of a Knative app.

kubectl apply -f $ITER8/samples/knative/quickstart/baseline.yaml
kubectl apply -f $ITER8/samples/knative/quickstart/experimentalservice.yaml
kubectl wait --for=condition=Ready ksvc/sample-app
Look inside baseline.yaml
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apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: sample-app
  namespace: default
spec:
  template:
    metadata:
      name: sample-app-v1
    spec:
      containers:
      - image: gcr.io/knative-samples/knative-route-demo:blue 
        env:
        - name: T_VERSION
          value: "blue"
Look inside experimentalservice.yaml
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apiVersion: serving.knative.dev/v1
kind: Service
metadata:
  name: sample-app
  namespace: default
spec:
  template:
    metadata:
      name: sample-app-v2
    spec:
      containers:
      - image: gcr.io/knative-samples/knative-route-demo:green 
        env:
        - name: T_VERSION
          value: "green"
  traffic:
  - tag: current
    revisionName: sample-app-v1
    percent: 100
  - tag: candidate
    latestRevision: true
    percent: 0

2. Define metrics

kubectl apply -f $ITER8/samples/knative/hybrid/metrics.yaml
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apiVersion: v1
kind: Namespace
metadata:
  name: iter8-knative
---
apiVersion: iter8.tools/v2alpha2
kind: Metric
metadata:
  name: user-engagement
  namespace: iter8-knative
spec:
  params:
  - name: nrql
    value: |
      SELECT average(duration) FROM Sessions WHERE version='$name' SINCE $elapsedTime sec ago
  description: Average duration of a session
  type: Gauge
  headerTemplates:
  - name: X-Query-Key
    value: t0p-secret-api-key  
  provider: newrelic
  jqExpression: ".results[0] | .[] | tonumber"
  urlTemplate: https://my-newrelic-service.com
  mock:
  - name: sample-app-v1
    level: 15.0
  - name: sample-app-v2
    level: 20.0
Metrics in your environment

You can define and use custom metrics from any database in Iter8 experiments.

For your application, replace the mocked user-engagement metric used in this tutorial with any custom metric you wish to optimize in the hybrid (A/B + SLOs) test. Documentation on defining custom metrics is here.

3. Launch experiment

kubectl apply -f $ITER8/samples/knative/hybrid/experiment.yaml
Look inside experiment.yaml
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apiVersion: iter8.tools/v2alpha2
kind: Experiment
metadata:
  name: hybrid-exp
spec:
  target: default/sample-app
  strategy:
    testingPattern: A/B
    deploymentPattern: Progressive
    actions:
      loop:
      - task: metrics/collect
        with:
          versions:
          - name: sample-app-v1
            url: http://sample-app-v1.default.svc.cluster.local
          - name: sample-app-v2
            url: http://sample-app-v2.default.svc.cluster.local
      finish: # run the following sequence of tasks at the end of the experiment
      - task: common/exec # promote the winning version      
        with:
          cmd: /bin/sh
          args:
          - "-c"
          - |
            kubectl apply -f https://raw.githubusercontent.com/iter8-tools/iter8/master/samples/knative/quickstart/{{ .promote }}.yaml
  criteria:
    rewards: # Business rewards
    - metric: iter8-knative/user-engagement
      preferredDirection: High # maximize user engagement
    objectives: 
    - metric: iter8-system/mean-latency
      upperLimit: 50
    - metric: iter8-system/latency-95th-percentile
      upperLimit: 100
    - metric: iter8-system/error-rate
      upperLimit: "0.01"
    requestCount: iter8-system/request-count
  duration:
    maxLoops: 10
    intervalSeconds: 1
    iterationsPerLoop: 1
  versionInfo:
    # information about app versions used in this experiment
    baseline:
      name: sample-app-v1
      weightObjRef:
        apiVersion: serving.knative.dev/v1
        kind: Service
        name: sample-app
        namespace: default
        fieldPath: .spec.traffic[0].percent
      variables:
      - name: promote
        value: baseline
    candidates:
    - name: sample-app-v2
      weightObjRef:
        apiVersion: serving.knative.dev/v1
        kind: Service
        name: sample-app
        namespace: default
        fieldPath: .spec.traffic[1].percent
      variables:
      - name: promote
        value: candidate

4. Observe experiment

Follow these steps to observe your experiment.

5. Cleanup

kubectl delete -f $ITER8/samples/knative/hybrid/experiment.yaml
kubectl delete -f $ITER8/samples/knative/quickstart/experimentalservice.yaml
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