Branch indexing and scanning in Jenkins - Commands & Configuration

Introduction

When you have many branches in your source code repository, Jenkins needs a way to find and manage them automatically. Branch indexing and scanning help Jenkins discover new branches and update existing ones so it can build them without manual setup.

When you want Jenkins to automatically detect new branches pushed to your Git repository and create jobs for them.

When you want to keep Jenkins jobs updated with changes in branch names or deletions.

When you manage multiple feature branches and want Jenkins to build each branch separately.

When you want to save time by avoiding manual job creation for every new branch.

When you want Jenkins to scan your repository regularly to keep branch jobs in sync.

Commands

This command updates or creates a Jenkins multibranch pipeline job using the configuration file. It sets up branch indexing and scanning based on the YAML file.

Terminal

jenkins-jobs --conf jenkins.ini update my-multibranch-job.yaml

Expected Output

Job 'my-multibranch-job' updated successfully

→

--conf - Specifies the Jenkins server configuration file

This command triggers branch indexing manually on the multibranch job to scan the repository and discover branches.

Terminal

curl -X POST http://localhost:8080/job/my-multibranch-job/indexing

Expected Output

No output (command runs silently)

This command fetches the list of branch jobs created by the multibranch pipeline and their build status.

Terminal

curl http://localhost:8080/job/my-multibranch-job/api/json?tree=jobs[name,color]

Expected Output

{"jobs":[{"name":"feature-1","color":"blue"},{"name":"feature-2","color":"blue"}]}

Key Concept

If you remember nothing else from branch indexing and scanning, remember: it lets Jenkins automatically find and manage all branches in your repository without manual job setup.

Common Mistakes

Not triggering branch indexing after creating or updating the multibranch job

Jenkins will not detect new or changed branches until indexing runs, so builds won't start for those branches.

Always trigger branch indexing manually or configure periodic indexing to keep branch jobs updated.

Using a single pipeline job instead of a multibranch pipeline for multiple branches

A single pipeline job cannot automatically detect or build multiple branches separately.

Use a multibranch pipeline job that supports branch indexing and scanning.

Summary

Use a multibranch pipeline job to let Jenkins manage multiple branches automatically.

Trigger branch indexing to scan the repository and discover branches.

Check branch jobs and their build status via Jenkins API or UI.

Practice

1. What is the main purpose of branch indexing in Jenkins Multibranch Pipeline jobs?

easy

A. To manually trigger builds for a single branch

B. To delete old builds from the Jenkins server

C. To automatically discover and build all branches in a repository

D. To configure user permissions for branches

Solution

1. Step 1: Understand branch indexing concept

   Branch indexing automatically finds all branches in a source code repository for Jenkins to build.

2. Step 2: Identify its main benefit

   This avoids manual job creation for each branch, saving time and effort.

3. Final Answer:

   To automatically discover and build all branches in a repository -> Option C

4. Quick Check:

   Branch indexing = automatic branch discovery [OK]

Hint: Branch indexing means Jenkins finds branches itself [OK]

Common Mistakes:

• Thinking branch indexing triggers manual builds only
• Confusing branch indexing with build cleanup
• Assuming it manages user permissions

2. Which Jenkins job type should you use to enable branch indexing and scanning?

easy

A. Multibranch Pipeline

B. Freestyle project

C. Matrix project

D. External job

Solution

1. Step 1: Identify job types in Jenkins

   Freestyle and Matrix projects do not support automatic branch discovery.

2. Step 2: Recognize Multibranch Pipeline features

   Multibranch Pipeline jobs are designed to scan repositories and index branches automatically.

3. Final Answer:

   Multibranch Pipeline -> Option A

4. Quick Check:

   Branch indexing requires Multibranch Pipeline job [OK]

Hint: Use Multibranch Pipeline for branch scanning [OK]

Common Mistakes:

• Choosing Freestyle project which lacks branch scanning
• Confusing Matrix project with Multibranch Pipeline
• Selecting External job which is unrelated

3. Given a Multibranch Pipeline job configured to scan every 1 hour, what happens when a new branch is pushed to the repository?

medium

A. Jenkins immediately builds the new branch

B. Jenkins ignores the new branch until manual scan

C. Jenkins deletes the new branch from the repository

D. Jenkins detects and indexes the new branch during the next scheduled scan

Solution

1. Step 1: Understand scan trigger timing

   The job is set to scan branches every 1 hour, not instantly.

2. Step 2: Predict behavior on new branch push

   Jenkins will detect and index the new branch during the next scheduled scan, not immediately.

3. Final Answer:

   Jenkins detects and indexes the new branch during the next scheduled scan -> Option D

4. Quick Check:

   Scheduled scan finds new branches [OK]

Hint: Scheduled scans find new branches, not instant builds [OK]

Common Mistakes:

• Assuming immediate build on branch push
• Thinking Jenkins ignores new branches without manual scan
• Believing Jenkins deletes new branches automatically

4. You configured a Multibranch Pipeline job but Jenkins does not detect new branches after pushing them. What is the most likely cause?

medium

A. The Jenkins server is offline

B. Branch indexing is disabled or scan trigger is not set

C. The repository URL is incorrect

D. The branches are deleted automatically after scan

Solution

1. Step 1: Check branch indexing settings

   If branch indexing or scan triggers are disabled, Jenkins won't detect new branches automatically.

2. Step 2: Consider other causes

   Incorrect repo URL or offline server would cause broader failures, not just missing branches.

3. Final Answer:

   Branch indexing is disabled or scan trigger is not set -> Option B

4. Quick Check:

   Branch indexing must be enabled for detection [OK]

Hint: Enable branch indexing and scan triggers to detect branches [OK]

Common Mistakes:

• Ignoring branch indexing settings
• Assuming Jenkins deletes branches automatically
• Blaming repository URL without checking indexing

5. How can you configure a Jenkins Multibranch Pipeline job to automatically build only branches matching the pattern feature/* during branch indexing?

hard

A. Set the Branch Sources filter with feature/* under 'Include branches matching' pattern

B. Manually create jobs for each feature branch

C. Use a post-build script to delete other branches

D. Configure the job to scan all branches without filters

Solution

1. Step 1: Use branch source filtering

   Jenkins Multibranch Pipeline allows filtering branches by patterns in the Branch Sources settings.

2. Step 2: Apply the pattern filter

   Setting 'Include branches matching' to feature/* ensures only those branches are indexed and built.

3. Final Answer:

   Set the Branch Sources filter with feature/* under 'Include branches matching' pattern -> Option A

4. Quick Check:

   Branch filters limit builds to matching branches [OK]

Hint: Use branch source filters to build specific branch patterns [OK]

Common Mistakes:

• Creating manual jobs instead of using filters
• Not applying branch filters and building all branches
• Using post-build scripts to filter branches incorrectly