README.md

Canary Deployment Strategy

• A Canary Deployment in Kubernetes is a strategy where a new version of an app is released to a small group of users first. If it works well, it’s gradually rolled out to everyone. This helps reduce the risk of issues affecting all users.

How it works ?

• Deploy New Version (Canary Release):
  • The new version of the application is first deployed to a small subset of users or a specific group of pods, called the canary.
  • This is typically a small fraction of the total traffic, so the new version gets tested by a limited audience while the majority of users continue to use the stable, old version.
• Traffic Splitting:
  • The traffic is split between the old version (the stable version) and the new version (the canary version).
  • Initially, a small percentage (e.g., 5–10%) of the traffic is routed to the new canary version, and the rest continues to go to the old version.
• Monitor and Analyze:
  • While the canary version is live, you monitor it for any errors or issues (like crashes, performance problems, etc.).
• Gradual Rollout:
  • If the canary version performs well, the percentage of traffic routed to the canary version is gradually increased.
  • This can be done in stages, such as 10%, 25%, 50%, and then 100%, depending on how confident you are with the new release.
  • The gradual increase reduces the risk of impacting all users if something goes wrong with the new version.

Pro's	Con's
Version released for subset of users	Slow rollout
Convenient for error rate and performance monitoring	Fine tune traffic distribution can be expensive

Note

This deployment strategy is suitable for Production environment.

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Prerequisites to try this:

1. EC2 Instance with Ubuntu OS

2. Docker installed & Configured

3. Kind Installed

4. Kubectl Installed

5. Kind Cluster running(Use kind-config.yml file present in this directory.)

Note

You have to go inside root dir of this repo and create Kind Cluster using command: kind create cluster --config kind-config.yml --name dep-strg

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Setup Steps

• Install the Ingress Controller for Kind

  # Apply the ingress controller manifest
  kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v1.8.2/deploy/static/provider/kind/deploy.yaml
  
  # Wait for the ingress controller to be ready
  kubectl wait --namespace ingress-nginx \
    --for=condition=ready pod \
    --selector=app.kubernetes.io/component=controller \
    --timeout=120s

• If the ingress controller pod remains in Pending state due to node selector issues, remove the node selector:

  kubectl patch deployment ingress-nginx-controller -n ingress-nginx --type=json \
    -p='[{"op": "remove", "path": "/spec/template/spec/nodeSelector"}]'

• Varify Ingress-Controller is running or not using command:

  kubectl get pods -n ingress-nginx

  

• Create the namespace

  kubectl apply -f canary-namespace.yml

• Deploy both versions with different replica counts

  # Deploy v1 (stable version - without footer)
  kubectl apply -f canary-v1-deployment.yaml  # 4 replicas (80% of traffic)
  
  # Deploy v2 (canary version - with footer)
  kubectl apply -f canary-v2-deployment.yaml  # 1 replica (20% of traffic)

• Create the combined service that selects both versions

  kubectl apply -f canary-combined-service.yaml

• Create the ingress for external access

  kubectl apply -f ingress.yaml

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How it works

1. Both deployments use the same app label (app: online-shop) but different version labels
2. The service selects pods based only on the app label, not the version
3. Traffic is distributed proportionally to the number of pods for each version:
   • v1 (without footer): 4 pods = ~80% of traffic
   • v2 (with footer): 1 pod = ~20% of traffic

---

Testing the Canary Deployment

• Using ingress

  kubectl port-forward -n ingress-nginx svc/ingress-nginx-controller 8080:80 --address 0.0.0.0 &

Then access http://<Instance_Ip>:8080 multiple times. You should see:

• The v1 version (without footer) approximately 80% of the time
• The v2 version (with footer) approximately 20% of the time

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Adjusting the Traffic Split

• To change the percentage of traffic going to each version, adjust the number of replicas:

  # Increase canary traffic to ~40% (3:2 ratio)
  kubectl scale deployment online-shop-v1 -n canary-ns --replicas=3
  kubectl scale deployment online-shop-v2 -n canary-ns --replicas=2
  
  # Increase canary traffic to ~60% (2:3 ratio)
  kubectl scale deployment online-shop-v1 -n canary-ns --replicas=2
  kubectl scale deployment online-shop-v2 -n canary-ns --replicas=3
  
  # Complete migration to v2 (0:5 ratio)
  kubectl scale deployment online-shop-v1 -n canary-ns --replicas=0
  kubectl scale deployment online-shop-v2 -n canary-ns --replicas=5

---

Monitoring

• Monitor your deployments during the canary process:

  # Check pods
  kubectl get pods -n canary-ns
  
  # Check the distribution of pods
  kubectl get pods -n canary-ns --show-labels
  
  # Check the service
  kubectl describe svc online-shop-service -n canary-ns

• Open a new tab of terminal, connnect EC2 instance and run the watch command to monitor the deployment

  watch kubectl get pods -n canary-ns

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Cleanup

• Deleting Kind Cluster:

  kind delete cluster --name dep-strg

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Note

If you cannot access the web app after the update, check your terminal — you probably encountered an error like:

error: lost connection to pod

Don’t worry! This happens because we’re running the cluster locally (e.g., with Kind), and the kubectl port-forward session breaks when the underlying pod is replaced during deployment (especially with Recreate strategy).

🔁 Just run the kubectl port-forward command again to re-establish the connection and access the app in your browser.

✅ This issue won't occur when deploying on managed Kubernetes services like AWS EKS, GKE, or AKS, because in those environments you usually expose services using NodePort, LoadBalancer, or Ingress — not kubectl port-forward.