Canary deployment pattern in Jenkins - Step-by-Step Execution

Process Flow - Canary deployment pattern

Start Deployment

↓

Deploy Canary Version

↓

Monitor Canary

↓

Promote

↓

Deploy Full

↓

End Deployment

This flow shows deploying a small subset (canary), monitoring it, then either promoting to full or rolling back based on results.

Execution Sample

Jenkins

pipeline {
  agent any
  parameters {
    booleanParam(name: 'canaryOk', defaultValue: false, description: 'Indicates if canary deployment is healthy')
  }
  stages {
    stage('Deploy Canary') {
      steps { echo 'Deploying canary version' }
    }
    stage('Monitor Canary') {
      steps { echo 'Monitoring canary health' }
    }
    stage('Promote or Rollback') {
      steps {
        script {
          if (params.canaryOk) {
            echo 'Promoting to full deployment'
          } else {
            echo 'Rolling back canary deployment'
          }
        }
      }
    }
  }
}

A Jenkins pipeline that deploys a canary, monitors it, then promotes or rolls back based on a parameter.

Process Table

Step	Action	Condition	Result	Output
1	Deploy Canary stage runs	N/A	Canary deployed	Deploying canary version
2	Monitor Canary stage runs	N/A	Canary monitored	Monitoring canary health
3	Check canaryOk parameter	canaryOk == true	Promote full deployment	Promoting to full deployment
4	End pipeline	N/A	Success	Pipeline completed
5	Alternative check	canaryOk == false	Rollback canary	Rolling back canary deployment
6	End pipeline	N/A	Failure handled	Pipeline completed with rollback

💡 Pipeline ends after promotion or rollback based on canaryOk parameter.

Status Tracker

Variable	Start	After Step 3	Final
params.canaryOk	undefined	true or false (set externally)	true or false (used to decide)

Key Moments - 3 Insights

Why do we deploy only a small part of the system first?

Deploying a small canary limits risk. If issues occur (see step 5 in execution_table), we rollback quickly without affecting all users.

What happens if the canary monitoring fails?

If monitoring shows problems (canaryOk == false), the pipeline rolls back the canary (step 5), preventing faulty code from reaching full deployment.

How does the pipeline decide to promote or rollback?

It uses the parameter 'canaryOk' checked in step 3. True promotes full deployment, false triggers rollback.

Visual Quiz - 3 Questions

Look at the execution_table, what output appears when the canary is healthy?

A Promoting to full deployment

B Deploying canary version

C Rolling back canary deployment

D Monitoring canary health

💡 Hint

Check row 3 in execution_table where canaryOk == true.

At which step does the pipeline decide to rollback the canary?

A Step 3

B Step 5

C Step 2

D Step 1

💡 Hint

Look for rollback action in execution_table rows.

If the canaryOk parameter is false, what is the final pipeline output?

A Pipeline completed

B Promoting to full deployment

C Pipeline completed with rollback

D Deploying canary version

💡 Hint

See the last row in execution_table for canaryOk == false.

Concept Snapshot

Canary deployment pattern in Jenkins:
- Deploy a small subset (canary) first
- Monitor canary health
- If healthy, promote to full deployment
- If issues, rollback canary
- Use parameters to control flow
- Minimizes risk by limiting exposure

Full Transcript

The canary deployment pattern in Jenkins starts by deploying a small part of the new version called the canary. Then the system monitors this canary for any problems. If the canary is healthy, the pipeline promotes the deployment to all users. If problems are detected, the pipeline rolls back the canary to avoid impacting everyone. This decision is controlled by a parameter called canaryOk. This approach reduces risk by testing changes on a small scale before full rollout.

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