Solution Deployment strategies

In this lesson, we will review the deployment strategies used in our lab exercise. This guide details how to identify the deployment strategy, verify service configurations, and gradually shift traffic between application versions for a safe rollout.

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Question 1: Identify the Deployment Strategy

Begin by identifying the deployment strategy used for the deployment in the default namespace.

1. List all deployments by running:
   root@controlplane ~ ➜ kubectl get deployments
   NAME      READY   UP-TO-DATE   AVAILABLE   AGE
   frontend  5/5     5            5           30s
   
2. Next, inspect the details of the “frontend” deployment to check its strategy:
   root@controlplane ~ ➜ kubectl describe deployment frontend
   Name:                   frontend
   Namespace:              default
   CreationTimestamp:      Thu, 04 Aug 2022 23:30:33 +0000
   Labels:                 app=myapp
                           tier=frontend
   Annotations:            deployment.kubernetes.io/revision: 1
   Selector:               app=frontend
   Replicas:               5 desired | 5 updated | 5 total | 5 available | 0 unavailable
   StrategyType:           RollingUpdate
   MinReadySeconds:        0
   RollingUpdateStrategy:  25% max unavailable, 25% max surge
   Pod Template:
     Labels:        app=frontend
                    version=v1
     Containers:
      webapp-color:
        Image:          kodekloud/webapp-color:v1
        Port:           <none>
        Host Port:      <none>
        Environment:    <none>
        Mounts:         <none>
     Volumes:        <none>
   Conditions:
     Type             Status  Reason
   

From the output, notice the deployment strategy is RollingUpdate.

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Question 2: Identify the Correct Service

The “frontend” deployment is connected to a NodePort service. Follow these steps to verify the service:

1. List the services:
   root@controlplane ~ ➜ kubectl get service
   NAME                TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)            AGE
   frontend-service    NodePort       10.97.89.251   <none>        8080:30080/TCP    65s
   kubernetes          ClusterIP      10.96.0.1      <none>        443/TCP           16m
   
2. Describe the service to inspect its configuration:
   root@controlplane ~ ➜ kubectl describe service frontend-service
   Name:                     frontend-service
   Namespace:                default
   Labels:                   app=myapp
   Annotations:              <none>
   Selector:                 app=frontend
   Type:                     NodePort
   IP Family Policy:         SingleStack
   IP Families:              IPv4
   

Since the service selector (app=frontend) matches the pod labels in the “frontend” deployment, the correct service is frontend-service.

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Question 3: Accessing the Web Application

To confirm that the web application is running, click the web app button provided in the interface. This step verifies that the application is accessible and functioning as expected.

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Question 4: Traffic Splitting with a New Deployment

A new deployment, frontend-v2, has been created in the default namespace with an updated image. The goal is to divert less than 20% of traffic to this new version, while keeping the total number of pods unchanged.

1. Verify both deployments:
   root@controlplane ~ ➜ kubectl get deployments
   NAME           READY   UP-TO-DATE   AVAILABLE   AGE
   frontend       5/5     5            5           2m43s
   frontend-v2    2/2     2            2           35s
   
   With the same selector (app=frontend), traffic is balanced across 7 pods (5 for frontend and 2 for frontend-v2), meaning frontend-v2 receives approximately 28% of the traffic.
2. To reduce the traffic to about 16.7%, scale down frontend-v2 to 1 replica:
   root@controlplane ~ ➜ kubectl scale deployment --replicas=1 frontend-v2
   deployment.apps/frontend-v2 scaled
   
3. Confirm the change:
   root@controlplane ~ ➜ kubectl get deployments
   NAME           READY   UP-TO-DATE   AVAILABLE   AGE
   frontend       5/5     5            5           4m52s
   frontend-v2    1/1     1            1           2m44s
   

With a total of 6 pods now running, frontend-v2 receives roughly 16.7% of the traffic. Refresh the application in your browser several times to observe any version changes when a request is routed to frontend-v2.

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Question 5: Redirect All Traffic to the New Version (v2)

Once you have confirmed that the new version functions correctly, safely redirect all traffic to frontend-v2 by following these steps:

1. Scale down the original frontend deployment:
   root@controlplane ~ ➜ kubectl scale deployment --replicas=0 frontend
   deployment.apps/frontend scaled
   
2. Scale up the frontend-v2 deployment to handle all traffic:
   root@controlplane ~ ➜ kubectl scale deployment --replicas=5 frontend-v2
   deployment.apps/frontend-v2 scaled
   
3. Verify the updates:
   root@controlplane ~ ➜ kubectl get deployments
   NAME           READY   UP-TO-DATE   AVAILABLE   AGE
   frontend       0/0     0            0           4m52s
   frontend-v2    5/5     5            5           2m44s
   
4. Finally, remove the old frontend deployment entirely:
   root@controlplane ~ ➜ kubectl delete deployment frontend
   

After reloading the application tab, only version 2 of the application should be active.

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This successful adjustment in the deployment strategy confirms that all user traffic is now routed to version 2 of the web application.