Why A/B testing with Ingress in Kubernetes? - Purpose & Use Cases

The Big Idea

What if you could test new features on real users without risking your whole website?

The Scenario

Imagine you want to test two versions of your website to see which one users like better. You try to do this by manually changing DNS settings or switching traffic between servers by hand.

The Problem

This manual way is slow and risky. You might send all users to the wrong version, cause downtime, or spend hours fixing mistakes. It's hard to control who sees what and to switch back quickly.

The Solution

Using A/B testing with Ingress in Kubernetes lets you automatically split user traffic between different versions of your app. It's fast, safe, and you can adjust the split anytime without downtime.

Before vs After

✗ Before

Change DNS records manually to point to version A or B

✓ After

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: ab-test-ingress
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: service-v1
            port:
              number: 80
      - path: /
        pathType: Prefix
        backend:
          service:
            name: service-v2
            port:
              number: 80
  # Traffic split handled by annotations or ingress controller features

What It Enables

You can safely test new features on real users and quickly decide which version works best without interrupting your service.

Real Life Example

A company launches a new checkout page design to 20% of users using Ingress A/B testing, collects feedback, then rolls it out to everyone if successful.

Key Takeaways

Manual traffic switching is slow and error-prone.

Ingress A/B testing automates safe traffic splitting.

This helps improve user experience with real-time testing.

Practice

1. What is the main purpose of using A/B testing with Kubernetes Ingress?

easy

A. To monitor CPU usage of pods

B. To increase the number of pods automatically

C. To split user traffic between different versions of an application

D. To backup Kubernetes cluster data

Solution

1. Step 1: Understand A/B testing concept in Kubernetes

   A/B testing with Ingress is used to route traffic between different app versions to test new features safely.

2. Step 2: Identify the purpose of Ingress in traffic management

   Ingress controls how external traffic reaches services, enabling traffic splitting for A/B testing.

3. Final Answer:

   To split user traffic between different versions of an application -> Option C

4. Quick Check:

   A/B testing = traffic split [OK]

Hint: A/B testing means splitting traffic between app versions [OK]

Common Mistakes:

• Confusing A/B testing with scaling pods
• Thinking Ingress is for monitoring only
• Assuming Ingress handles backups

2. Which annotation is commonly used in Kubernetes Ingress to split traffic by percentage for A/B testing?

easy

A. nginx.ingress.kubernetes.io/canary-weight

B. nginx.ingress.kubernetes.io/rewrite-target

C. nginx.ingress.kubernetes.io/ssl-redirect

D. nginx.ingress.kubernetes.io/proxy-body-size

Solution

1. Step 1: Identify annotations for traffic splitting

   The annotation 'nginx.ingress.kubernetes.io/canary-weight' is used to specify the percentage of traffic sent to the canary version.

2. Step 2: Differentiate from other annotations

   Other annotations like rewrite-target or ssl-redirect serve different purposes unrelated to traffic splitting.

3. Final Answer:

   nginx.ingress.kubernetes.io/canary-weight -> Option A

4. Quick Check:

   Canary weight = traffic percentage [OK]

Hint: Look for 'canary-weight' to split traffic by percent [OK]

Common Mistakes:

• Using rewrite-target for traffic splitting
• Confusing SSL redirect with traffic control
• Ignoring canary annotations

3. Given this Ingress snippet for A/B testing, what percentage of traffic goes to the canary service?

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
  annotations:
    nginx.ingress.kubernetes.io/canary: "true"
    nginx.ingress.kubernetes.io/canary-weight: "30"
spec:
  rules:
  - host: example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: stable-service
            port:
              number: 80
      - path: /
        pathType: Prefix
        backend:
          service:
            name: canary-service
            port:
              number: 80

medium

A. 70%

B. 30%

C. 50%

D. 100%

Solution

1. Step 1: Read the canary-weight annotation

   The annotation 'nginx.ingress.kubernetes.io/canary-weight' is set to "30", meaning 30% of traffic goes to canary.

2. Step 2: Understand traffic split logic

   Traffic is split by percentage; 30% to canary-service, remaining 70% to stable-service.

3. Final Answer:

   30% -> Option B

4. Quick Check:

   Canary weight = 30% traffic [OK]

Hint: Check canary-weight value for traffic percent [OK]

Common Mistakes:

• Assuming canary gets 70% instead of 30%
• Confusing service names with traffic percentages
• Ignoring canary annotation

4. You configured this Ingress for A/B testing but all traffic goes to the stable service only. What is the likely error?

metadata:
  annotations:
    nginx.ingress.kubernetes.io/canary: "true"
    nginx.ingress.kubernetes.io/canary-weight: "50"
spec:
  rules:
  - host: test.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: stable-service
            port:
              number: 80

medium

A. Missing canary backend path in spec

B. Incorrect canary-weight value format

C. Host name is invalid

D. Stable service port is wrong

Solution

1. Step 1: Check Ingress spec for canary backend

   The spec only has one backend for stable-service; no path defined for canary-service.

2. Step 2: Understand traffic routing requirements

   For canary traffic to work, a separate path with canary annotations and backend service must be defined.

3. Final Answer:

   Missing canary backend path in spec -> Option A

4. Quick Check:

   Canary needs separate backend path [OK]

Hint: Ensure canary backend path exists in Ingress spec [OK]

Common Mistakes:

• Assuming canary-weight alone routes traffic
• Ignoring missing canary backend path
• Blaming host or port without checking paths

5. You want to route 20% of users with header X-User-Type: beta to the canary service and the rest to stable. Which Ingress annotation setup achieves this?

hard

A. Use nginx.ingress.kubernetes.io/canary-by-cookie: "beta"

B. Use nginx.ingress.kubernetes.io/canary-weight: "20" only

C. Use nginx.ingress.kubernetes.io/canary: "false"

D. Use nginx.ingress.kubernetes.io/canary-by-header: "X-User-Type" and nginx.ingress.kubernetes.io/canary-by-header-value: "beta"

Solution

1. Step 1: Identify header-based routing annotations

   To route traffic based on header, use 'canary-by-header' and 'canary-by-header-value' annotations.

2. Step 2: Understand difference from weight-based routing

   Weight-based routing splits traffic by percentage regardless of headers; header-based routing targets specific users.

3. Final Answer:

   Use nginx.ingress.kubernetes.io/canary-by-header: "X-User-Type" and nginx.ingress.kubernetes.io/canary-by-header-value: "beta" -> Option D

4. Quick Check:

   Header-based routing uses canary-by-header annotations [OK]

Hint: Use canary-by-header and canary-by-header-value for header routing [OK]

Common Mistakes:

• Using only canary-weight for header routing
• Confusing cookie-based routing with header routing
• Setting canary to false disables routing