Blue-green deployment pattern in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the two environments used in blue-green deployment.

Jenkins

def deployTo[1]() {
    echo 'Deploying to environment'
}

Drag options to blanks, or click blank then click option'

Agreen

Bblue

Ctest

Dprod

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'test' or 'prod' instead of 'blue' or 'green'.

The blue-green deployment pattern uses two environments named 'blue' and 'green'. Here, 'blue' is used as the environment name.

2fill in blank

medium

Complete the code to switch traffic to the new environment in blue-green deployment.

Jenkins

stage('Switch Traffic') {
    steps {
        script {
            sh 'kubectl [1] service blue-service green-service'
        }
    }
}

Drag options to blanks, or click blank then click option'

Apatch

Breplace

Cdelete

Drollout

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'delete' which removes the service, causing downtime.

In blue-green deployment, 'kubectl patch' is used to switch the service from blue to green environment smoothly.

3fill in blank

hard

Fix the error in the Jenkins pipeline step to deploy to the green environment.

Jenkins

stage('Deploy Green') {
    steps {
        [1] 'deploy-green.sh'
    }
}

Drag options to blanks, or click blank then click option'

Ash

Bpowershell

Cbat

Dscript

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'bat' which is for Windows batch scripts.

The 'sh' step runs shell scripts in Jenkins pipelines on Unix-like agents. Here, it correctly runs 'deploy-green.sh'.

4fill in blank

hard

Fill both blanks to create a Jenkins stage that deploys to blue and green environments sequentially.

Jenkins

stage('Deploy Both') {
    steps {
        [1] 'deploy-[2].sh'
    }
}

Drag options to blanks, or click blank then click option'

Ash

Bbat

Cblue

Dgreen

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'bat' on Unix agents or wrong environment name.

The 'sh' step runs shell scripts. The script name includes the environment name, here 'blue'.

5fill in blank

hard

Fill all three blanks to define a Jenkins pipeline snippet that deploys to green, switches traffic, and verifies deployment.

Jenkins

pipeline {
    agent any
    stages {
        stage('Deploy Green') {
            steps {
                [1] 'deploy-green.sh'
            }
        }
        stage('Switch Traffic') {
            steps {
                script {
                    sh 'kubectl [2] service blue-service green-service'
                }
            }
        }
        stage('Verify') {
            steps {
                [3] 'curl -f http://green.example.com/health'
            }
        }
    }
}

Drag options to blanks, or click blank then click option'

Ash

Bpatch

Dbat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'bat' on Unix agents or wrong kubectl command.

The 'sh' step runs shell commands for deployment and verification. 'kubectl patch' switches traffic to green.

Practice

1. What is the main goal of the blue-green deployment pattern in Jenkins?

easy

A. To deploy only on weekends

B. To run tests faster by using multiple agents

C. To backup data before deployment

D. To avoid downtime by switching between two identical environments

Solution

1. Step 1: Understand blue-green deployment concept

   This pattern uses two identical environments called blue and green to deploy new versions without downtime.

2. Step 2: Identify the main goal in Jenkins context

   Jenkins automates switching traffic between these environments to keep the service available during updates.

3. Final Answer:

   To avoid downtime by switching between two identical environments -> Option D

4. Quick Check:

   Blue-green deployment = avoid downtime [OK]

Hint: Blue-green means two environments for zero downtime [OK]

Common Mistakes:

• Confusing blue-green with backup strategies
• Thinking it speeds up tests
• Assuming deployment timing is the main goal

2. Which Jenkins pipeline step correctly switches traffic from the blue environment to the green environment?

easy

A. sh 'kubectl patch service myapp -p "{\"spec\":{\"selector\":{\"env\":\"green\"}}}'

B. sh 'kubectl apply -f green-service.yaml'

C. sh 'kubectl scale deployment blue --replicas=0'

D. sh 'kubectl delete pod blue-pod-1'

Solution

1. Step 1: Understand traffic switching in Kubernetes

   Switching traffic means updating the service selector to point to the new environment pods.

2. Step 2: Identify the correct kubectl command

   The patch command changes the service selector to 'green', redirecting traffic from blue to green.

3. Final Answer:

   sh 'kubectl patch service myapp -p "{\"spec\":{\"selector\":{\"env\":\"green\"}}}' -> Option A

4. Quick Check:

   Patch service selector = switch traffic [OK]

Hint: Patch service selector to switch environments [OK]

Common Mistakes:

• Scaling down blue does not switch traffic immediately
• Applying green service config alone doesn't switch traffic
• Deleting pods causes downtime

3. Given this Jenkins pipeline snippet, what will be the output if the green environment is healthy?

stage('Deploy Green') {
  steps {
    sh 'kubectl apply -f green-deployment.yaml'
    sh 'kubectl rollout status deployment/green'
  }}
stage('Switch Traffic') {
  steps {
    sh 'kubectl patch service myapp -p "{\"spec\":{\"selector\":{\"env\":\"green\"}}}'
  }}

medium

A. Traffic remains on blue environment

B. Deployment fails because green environment is missing

C. Deployment applies and traffic switches to green with no errors

D. Rollout status command causes syntax error

Solution

1. Step 1: Analyze deployment commands

   The green deployment is applied and rollout status waits for it to be ready.

2. Step 2: Analyze traffic switch command

   The patch command updates the service selector to green, switching traffic successfully.

3. Final Answer:

   Deployment applies and traffic switches to green with no errors -> Option C

4. Quick Check:

   Healthy green + patch service = success [OK]

Hint: Healthy rollout then patch service switches traffic [OK]

Common Mistakes:

• Assuming rollout status causes errors
• Thinking traffic stays on blue after patch
• Confusing deployment apply with service patch

4. You have a Jenkins pipeline that deploys to green, but users report downtime after switching traffic. What is the most likely cause?

medium

A. The Jenkinsfile syntax is incorrect

B. The green deployment rollout was not completed before switching traffic

C. The blue environment was deleted before switching

D. The service selector was not patched to green

Solution

1. Step 1: Understand downtime cause in blue-green

   Downtime happens if traffic switches before the new environment is ready.

2. Step 2: Identify pipeline mistake

   If rollout status is skipped or incomplete, green pods may not be ready, causing downtime.

3. Final Answer:

   The green deployment rollout was not completed before switching traffic -> Option B

4. Quick Check:

   Incomplete rollout before switch = downtime [OK]

Hint: Wait for rollout status before switching traffic [OK]

Common Mistakes:

• Deleting blue early does not cause downtime if green is ready
• Syntax errors cause pipeline failure, not downtime
• Not patching service keeps old traffic, no downtime

5. In a Jenkins pipeline implementing blue-green deployment, how can you safely clean up the old environment after switching traffic to green?

hard

A. Scale down the blue deployment to zero replicas after verifying green is stable

B. Delete the blue deployment immediately after patching the service

C. Keep both blue and green running indefinitely

D. Restart Jenkins to clear old environment

Solution

1. Step 1: Understand cleanup in blue-green deployment

   After switching traffic, the old environment should be scaled down to free resources but kept until stability is confirmed.

2. Step 2: Identify safe cleanup method in Jenkins pipeline

   Scaling down blue to zero replicas after green is stable avoids downtime and allows rollback if needed.

3. Final Answer:

   Scale down the blue deployment to zero replicas after verifying green is stable -> Option A

4. Quick Check:

   Scale down old env after stable new env [OK]

Hint: Scale down old env only after new env is stable [OK]

Common Mistakes:

• Deleting old deployment immediately risks downtime
• Keeping both running wastes resources
• Restarting Jenkins does not affect deployments