Multi-branch pipeline job creation in Jenkins - Step-by-Step Execution

Process Flow - Multi-branch pipeline job creation

Start Jenkins

↓

Create Multi-branch Pipeline Job

↓

Configure SCM Repository

↓

Scan Branches

↓

For each branch found

↓

Create Pipeline Job for Branch

↓

Run Pipeline Job

↓

Collect Results

↓

End

This flow shows how Jenkins creates a multi-branch pipeline job, scans branches in the repository, creates jobs for each branch, and runs them.

Execution Sample

Jenkins

pipeline {
  agent any
  stages {
    stage('Build') {
      steps { echo "Building branch ${env.BRANCH_NAME}" }
    }
  }
}

A simple Jenkins pipeline script that prints the branch name during the build stage.

Process Table

Step	Action	Details	Result
1	Start Jenkins	Jenkins server starts	Ready to create jobs
2	Create Multi-branch Pipeline Job	Job named 'MyMultiBranchJob' created	Job created with SCM config
3	Configure SCM Repository	Set Git URL to https://github.com/example/repo.git	SCM linked
4	Scan Branches	Jenkins scans repo branches	Branches found: main, dev, feature1
5	Create Pipeline Job for Branch 'main'	Job created for 'main'	Job ready to run
6	Create Pipeline Job for Branch 'dev'	Job created for 'dev'	Job ready to run
7	Create Pipeline Job for Branch 'feature1'	Job created for 'feature1'	Job ready to run
8	Run Pipeline Job for 'main'	Pipeline script runs	Output: Building branch main
9	Run Pipeline Job for 'dev'	Pipeline script runs	Output: Building branch dev
10	Run Pipeline Job for 'feature1'	Pipeline script runs	Output: Building branch feature1
11	Collect Results	Jobs completed	Build results collected
12	End	All branches processed	Multi-branch pipeline complete

💡 All branches scanned and pipeline jobs executed successfully

Status Tracker

Variable	Start	After Step 4	After Step 7	Final
Branches Found	[]	[main, dev, feature1]	[main, dev, feature1]	[main, dev, feature1]
Jobs Created	0	0	3	3
Build Output	""	""	""	"Building branch main\nBuilding branch dev\nBuilding branch feature1"

Key Moments - 3 Insights

Why does Jenkins create separate jobs for each branch?

Because the multi-branch pipeline scans the repository and creates a job per branch to run pipelines independently, as shown in steps 5-7.

What happens if a new branch is added after the initial scan?

Jenkins will detect it on the next scan and create a new job for that branch, similar to the initial scan process in step 4.

Why do pipeline jobs print the branch name during the build?

The pipeline uses the environment variable BRANCH_NAME to identify the current branch, demonstrated in the build output in steps 8-10.

Visual Quiz - 3 Questions

Look at the execution table, at which step does Jenkins find the branches in the repository?

A Step 8

B Step 2

C Step 4

D Step 10

💡 Hint

Check the 'Action' column for scanning branches in the execution table.

According to the variable tracker, how many jobs are created after step 7?

A 3

B 1

C 0

D 5

💡 Hint

Look at the 'Jobs Created' row under 'After Step 7' in the variable tracker.

If a new branch 'hotfix' is added after step 4, what will happen next?

A Jenkins ignores it

B Jenkins creates a new job for 'hotfix' on next scan

C Jenkins deletes all jobs

D Jenkins merges 'hotfix' with 'main'

💡 Hint

Refer to key moment about new branches being detected on scans.

Concept Snapshot

Multi-branch pipeline job creation in Jenkins:
- Create a multi-branch pipeline job
- Configure SCM repository URL
- Jenkins scans branches automatically
- Creates pipeline jobs per branch
- Runs pipelines independently per branch
- Uses BRANCH_NAME env variable in scripts

Full Transcript

This visual execution shows how Jenkins creates a multi-branch pipeline job. First, Jenkins starts and the user creates a multi-branch pipeline job. Then, the SCM repository URL is configured. Jenkins scans the repository branches and finds multiple branches like main, dev, and feature1. For each branch, Jenkins creates a separate pipeline job. Each job runs the pipeline script, which prints the branch name using the BRANCH_NAME environment variable. After all jobs run, Jenkins collects the results and completes the multi-branch pipeline process. Variables like branches found and jobs created update step-by-step. Key moments clarify why Jenkins creates jobs per branch and how new branches are handled. The quiz tests understanding of scanning steps, job creation count, and branch addition behavior.

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