Multi-branch pipeline job creation in Jenkins - Commands & Configuration

Introduction

Managing multiple branches in a project can be complex. A multi-branch pipeline job in Jenkins automatically creates and runs pipelines for each branch, saving time and reducing manual setup.

When you have a project with many branches and want Jenkins to build each branch automatically.

When you want to test feature branches separately without creating jobs manually.

When you want to keep your CI/CD process organized by branch.

When you want Jenkins to detect new branches and run pipelines without extra configuration.

When you want to apply the same pipeline script to all branches in your repository.

Config File - Jenkinsfile

Jenkinsfile

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                echo 'Building the project'
            }
        }
        stage('Test') {
            steps {
                echo 'Running tests'
            }
        }
        stage('Deploy') {
            steps {
                echo 'Deploying application'
            }
        }
    }
}

This Jenkinsfile defines a simple pipeline with three stages: Build, Test, and Deploy. It runs on any available agent. This file should be placed in the root of each branch so Jenkins can run the same pipeline for all branches automatically.

Commands

This command creates a new multi-branch pipeline job named 'example-multibranch' in Jenkins, pointing to the specified Git repository URL. Jenkins will scan all branches and run pipelines based on the Jenkinsfile in each branch.

Terminal

jenkins-jobs create-multibranch-pipeline --name example-multibranch --git-url https://github.com/example-user/example-repo.git

Expected Output

Created multi-branch pipeline job 'example-multibranch' pointing to https://github.com/example-user/example-repo.git

→

--name - Specifies the name of the multi-branch pipeline job

→

--git-url - Specifies the Git repository URL to scan for branches

This command tells Jenkins to scan the 'example-multibranch' job for branches and create pipeline runs for each branch found.

Terminal

jenkins-jobs scan-multibranch example-multibranch

Expected Output

Scanning multi-branch pipeline job 'example-multibranch' for branches...

Found branches: main, feature-1, bugfix-2

Triggering builds for new branches...

This command lists the builds triggered by the multi-branch pipeline job, showing the status of each branch's pipeline run.

Terminal

jenkins-jobs list-builds example-multibranch

Expected Output

Branch: main - SUCCESS

Branch: feature-1 - RUNNING

Branch: bugfix-2 - SUCCESS

Key Concept

If you remember nothing else from this pattern, remember: a multi-branch pipeline job automatically detects and runs pipelines for all branches using the Jenkinsfile in each branch.

Common Mistakes

Not placing a Jenkinsfile in each branch

Jenkins cannot run a pipeline for branches without a Jenkinsfile, so those branches will be skipped.

Ensure every branch has a Jenkinsfile at the root with the pipeline definition.

Using incorrect Git repository URL when creating the job

Jenkins will fail to scan branches if the URL is wrong or inaccessible.

Double-check the Git URL and ensure Jenkins has access permissions.

Not scanning the multi-branch job after creation

Without scanning, Jenkins will not detect new branches or trigger builds.

Run the scan command or configure automatic branch indexing in Jenkins.

Summary

Create a multi-branch pipeline job pointing to your Git repository to manage all branches automatically.

Place a Jenkinsfile in each branch to define the pipeline steps.

Scan the multi-branch job to detect branches and trigger builds.

Check build status for each branch to monitor pipeline runs.

Practice

1. What is the main purpose of a multi-branch pipeline job in Jenkins?

easy

A. To automatically create and manage pipeline jobs for each branch in a repository

B. To run a single pipeline job for all branches combined

C. To manually configure pipelines for each branch separately

D. To deploy applications without building them

Solution

1. Step 1: Understand multi-branch pipeline concept

   A multi-branch pipeline job automatically detects branches in a source code repository and creates pipeline jobs for each branch.

2. Step 2: Compare options with concept

   To automatically create and manage pipeline jobs for each branch in a repository correctly describes this automation. Options B, C, and D do not match the automatic branch job creation feature.

3. Final Answer:

   To automatically create and manage pipeline jobs for each branch in a repository -> Option A

4. Quick Check:

   Multi-branch pipeline = automatic branch job creation [OK]

Hint: Multi-branch pipelines auto-create jobs per branch [OK]

Common Mistakes:

• Thinking it runs one job for all branches
• Assuming manual job creation is needed
• Confusing deployment with pipeline creation

2. Which Jenkinsfile location is automatically used by a multi-branch pipeline job for each branch?

easy

A. Only in the main branch

B. In a separate centralized folder outside branches

C. In the root directory of each branch

D. In the Jenkins server workspace

Solution

1. Step 1: Identify Jenkinsfile location for multi-branch pipelines

   Multi-branch pipelines look for a Jenkinsfile in the root directory of each branch to define that branch's pipeline.

2. Step 2: Evaluate options

   In the root directory of each branch matches this behavior. Options B, C, and D do not reflect the automatic per-branch Jenkinsfile usage.

3. Final Answer:

   In the root directory of each branch -> Option C

4. Quick Check:

   Jenkinsfile location = root of each branch [OK]

Hint: Jenkinsfile must be in branch root for multi-branch jobs [OK]

Common Mistakes:

• Thinking Jenkinsfile is centralized outside branches
• Assuming only main branch Jenkinsfile is used
• Believing Jenkinsfile is stored on Jenkins server

3. Given a multi-branch pipeline job configured to scan a Git repository with branches main and feature1, what happens when a new branch feature2 is pushed?

medium

A. The job automatically detects feature2 and creates a new pipeline for it

B. The job ignores feature2 until manually added

C. The job deletes pipelines for main and feature1

D. The job merges feature2 into main automatically

Solution

1. Step 1: Understand scan trigger behavior

   Multi-branch pipeline jobs scan the repository and detect new branches automatically, creating pipelines for them.

2. Step 2: Analyze options

   The job automatically detects feature2 and creates a new pipeline for it correctly states the automatic detection and pipeline creation for feature2. Options A, B, and D describe incorrect behaviors.

3. Final Answer:

   The job automatically detects feature2 and creates a new pipeline for it -> Option A

4. Quick Check:

   New branch detected = new pipeline created [OK]

Hint: New branches auto-create pipelines on scan [OK]

Common Mistakes:

• Assuming manual addition of new branches
• Thinking existing pipelines get deleted
• Confusing pipeline creation with branch merging

4. You created a multi-branch pipeline job but it does not detect any branches. What is the most likely cause?

medium

A. The Jenkinsfile is missing in the main branch only

B. The repository URL is incorrect or inaccessible

C. The Jenkins server is offline

D. The job is set to build only tags, not branches

Solution

1. Step 1: Check repository access

   If the multi-branch pipeline job cannot detect branches, the most common cause is an incorrect or inaccessible repository URL.

2. Step 2: Evaluate other options

   The Jenkinsfile is missing in the main branch only is less likely because missing Jenkinsfile in main branch does not prevent branch detection. The Jenkins server is offline is unrelated if Jenkins is running. The job is set to build only tags, not branches is possible but less common than repository access issues.

3. Final Answer:

   The repository URL is incorrect or inaccessible -> Option B

4. Quick Check:

   Branch detection fails if repo URL is wrong [OK]

Hint: Check repo URL first if no branches detected [OK]

Common Mistakes:

• Blaming missing Jenkinsfile for no branch detection
• Ignoring repository access permissions
• Assuming Jenkins server is offline without checking

5. You want to configure a multi-branch pipeline job to scan your GitHub repo every 15 minutes to detect new branches or changes. Which Jenkins feature should you use?

hard

A. Use a freestyle job to poll the repository

B. Manually run the scan from Jenkins dashboard each time

C. Configure a webhook in GitHub but disable Jenkins scanning

D. Set a periodic scan trigger with a cron expression like H/15 * * * *

Solution

1. Step 1: Identify scan trigger configuration

   Multi-branch pipeline jobs support periodic scanning using cron syntax to detect branch changes automatically.

2. Step 2: Analyze options

   Set a periodic scan trigger with a cron expression like H/15 * * * * correctly describes setting a periodic scan trigger with cron. Manually run the scan from Jenkins dashboard each time is manual, not automatic. Configure a webhook in GitHub but disable Jenkins scanning disables Jenkins scanning, so no detection. Use a freestyle job to poll the repository uses freestyle job, not multi-branch pipeline.

3. Final Answer:

   Set a periodic scan trigger with a cron expression like H/15 * * * * -> Option D

4. Quick Check:

   Periodic scan trigger = automatic branch updates [OK]

Hint: Use cron trigger for automatic branch scanning [OK]

Common Mistakes:

• Relying only on manual scans
• Disabling Jenkins scan but using webhooks only
• Using freestyle jobs instead of multi-branch pipelines