Canary deployment pattern in Jenkins - Mini Project: Build & Apply

Canary Deployment Pattern with Jenkins

📖 Scenario: You work as a DevOps engineer in a company that wants to release new versions of their web application safely. Instead of updating all users at once, they want to try the new version on a small group first. This is called a canary deployment. You will create a simple Jenkins pipeline script to automate this process.

🎯 Goal: Build a Jenkins pipeline script that deploys a new version of an application to a small group of users first (canary), waits for approval, and then deploys to all users.

📋 What You'll Learn

Create a variable for the canary group size

Add a stage to deploy to the canary group

Add a manual approval step before full deployment

Add a stage to deploy to all users after approval

💡 Why This Matters

🌍 Real World

Canary deployments help companies release new software versions safely by testing on a small group first, reducing risk.

💼 Career

Understanding canary deployments and Jenkins pipelines is essential for DevOps engineers to automate safe software releases.

1

Set up the canary group size variable

Create a variable called canaryGroupSize and set it to 10 to represent the number of users in the canary group.

Jenkins

# Create a variable called canaryGroupSize and set it to 10
# Your code here

Hint

Use def canaryGroupSize = 10 to create the variable.

2

Add a stage to deploy to the canary group

Add a stage named 'Deploy Canary' that prints "Deploying to canary group of size 10" using the canaryGroupSize variable.

Jenkins

def canaryGroupSize = 10

// Add a stage named 'Deploy Canary' that prints the deployment message
// Your code here

Hint

Use stage('Deploy Canary') and inside steps use echo with the variable.

3

Add a manual approval step before full deployment

Add a stage named 'Approval' with an input step that asks 'Approve full deployment?' before continuing.

Jenkins

def canaryGroupSize = 10

pipeline {
    agent any
    stages {
        stage('Deploy Canary') {
            steps {
                echo "Deploying to canary group of size ${canaryGroupSize}"
            }
        }
        // Add a stage named 'Approval' with an input step
        // Your code here
    }
}

Hint

Use stage('Approval') and inside steps add input message: 'Approve full deployment?'.

4

Add a stage to deploy to all users after approval

Add a stage named 'Deploy Full' that prints "Deploying to all users" after the approval stage.

Jenkins

def canaryGroupSize = 10

pipeline {
    agent any
    stages {
        stage('Deploy Canary') {
            steps {
                echo "Deploying to canary group of size ${canaryGroupSize}"
            }
        }
        stage('Approval') {
            steps {
                input message: 'Approve full deployment?'
            }
        }
        // Add a stage named 'Deploy Full' that prints deployment message
        // Your code here
    }
}

Hint

Use stage('Deploy Full') and inside steps add echo "Deploying to all users".

Practice

1. What is the main purpose of a canary deployment in Jenkins?

easy

A. To release updates to a small group first to reduce risk

B. To deploy all changes to production at once

C. To rollback all changes immediately after deployment

D. To skip testing and deploy directly

Solution

1. Step 1: Understand canary deployment concept

   Canary deployment means releasing updates to a small subset of users first to catch issues early.

2. Step 2: Compare options with this concept

   Only To release updates to a small group first to reduce risk describes releasing to a small group to reduce risk, matching the canary pattern.

3. Final Answer:

   To release updates to a small group first to reduce risk -> Option A

4. Quick Check:

   Canary deployment = small group release [OK]

Hint: Canary means small group first to catch problems early [OK]

Common Mistakes:

• Thinking canary deploys to all users at once
• Confusing canary with rollback process
• Assuming canary skips testing

2. Which Jenkins Pipeline syntax correctly defines separate stages for canary and full deployment?

easy

A. steps { stage('Canary') { echo 'Deploying canary' } stage('Full') { echo 'Deploying full' } }

B. stage('Deploy') { steps { echo 'Deploying canary and full together' } }

C. stage('Canary') { steps { echo 'Deploying canary' } } stage('Full') { steps { echo 'Deploying full' } }

D. stage('Canary and Full') { steps { echo 'Deploying both' } }

Solution

1. Step 1: Identify correct Jenkins Pipeline stage syntax

   Each stage must be defined with stage('name') { steps { ... } } blocks.

2. Step 2: Check which option uses separate stages for canary and full deployment

   stage('Canary') { steps { echo 'Deploying canary' } } stage('Full') { steps { echo 'Deploying full' } } correctly defines two separate stages named 'Canary' and 'Full' with steps inside.

3. Final Answer:

   stage('Canary') { steps { echo 'Deploying canary' } } stage('Full') { steps { echo 'Deploying full' } } -> Option C

4. Quick Check:

   Separate stages = stage('Canary') { steps { echo 'Deploying canary' } } stage('Full') { steps { echo 'Deploying full' } } [OK]

Hint: Separate canary and full deploy in different stages [OK]

Common Mistakes:

• Putting stages inside steps block incorrectly
• Combining canary and full in one stage
• Missing steps block inside stage

3. Given this Jenkins Pipeline snippet, what will be the output during the canary stage?

pipeline {
  agent any
  stages {
    stage('Canary') {
      steps {
        echo 'Starting canary deployment'
      }
    }
    stage('Full') {
      steps {
        echo 'Starting full deployment'
      }
    }
  }
}

medium

A. Starting canary deployment\nStarting full deployment

B. Starting full deployment

C. Starting canary deployment

D. No output

Solution

1. Step 1: Understand Jenkins Pipeline stage execution

   Stages run sequentially. The 'Canary' stage runs first and prints its echo message, then the 'Full' stage runs and prints its message.

2. Step 2: Identify output during the entire pipeline run

   When the pipeline runs fully, both 'Starting canary deployment' and 'Starting full deployment' are printed sequentially.

3. Final Answer:

   Starting canary deployment Starting full deployment -> Option A

4. Quick Check:

   Pipeline output = both stage messages in order [OK]

Hint: Each stage prints its own echo message when running sequentially [OK]

Common Mistakes:

• Assuming all stages print output at once
• Confusing canary stage output with full stage
• Thinking no output appears during stages

4. You wrote this Jenkins Pipeline snippet for canary deployment but it fails with syntax error:

pipeline {
  agent any
  stages {
    stage('Canary')
      steps {
        echo 'Deploying canary'
      }
    }
  }
}

What is the error?

medium

A. Extra closing brace after steps block

B. Incorrect agent declaration

C. Missing echo command inside steps

D. Missing curly braces after stage('Canary') declaration

Solution

1. Step 1: Check stage syntax in Jenkins Pipeline

   The stage('Canary') must be followed by a block enclosed in curly braces { ... }.

2. Step 2: Identify missing braces causing syntax error

   The snippet misses opening curly brace after stage('Canary'), causing syntax error.

3. Final Answer:

   Missing curly braces after stage('Canary') declaration -> Option D

4. Quick Check:

   Stage needs braces {} after declaration [OK]

Hint: Always add braces {} after stage('name') [OK]

Common Mistakes:

• Forgetting braces after stage declaration
• Misplacing steps block outside stage
• Incorrect indentation causing confusion

5. You want to implement a canary deployment in Jenkins that deploys to 10% of users first, then 100% if no errors. Which approach best fits this requirement?

hard

A. Deploy 100% immediately and rollback if errors occur

B. Use separate Jenkins stages: one for 10% canary deploy, monitor, then full deploy stage

C. Deploy 10% and skip monitoring to save time

D. Deploy 50% first, then 50% later without monitoring

Solution

1. Step 1: Understand canary deployment best practice

   Canary deployment requires deploying to a small subset (10%) first, then monitoring for errors before full rollout.

2. Step 2: Match approach to requirement

   Use separate Jenkins stages: one for 10% canary deploy, monitor, then full deploy stage uses separate stages for canary and full deployment with monitoring in between, fitting the requirement best.

3. Final Answer:

   Use separate Jenkins stages: one for 10% canary deploy, monitor, then full deploy stage -> Option B

4. Quick Check:

   Canary deploy + monitor + full deploy = Use separate Jenkins stages: one for 10% canary deploy, monitor, then full deploy stage [OK]

Hint: Deploy small group, monitor, then full deploy [OK]

Common Mistakes:

• Skipping monitoring after canary deploy
• Deploying full immediately without canary
• Choosing wrong canary percentage