Branch indexing and scanning in Jenkins - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is branch indexing in Jenkins?

Branch indexing is the process Jenkins uses to discover all branches in a source code repository so it can create or update jobs for each branch automatically.

beginner

What does branch scanning do in Jenkins Multibranch Pipeline?

Branch scanning checks the repository for new, changed, or deleted branches and updates Jenkins jobs accordingly to keep builds in sync with the repository.

intermediate

How often does Jenkins perform branch indexing by default?

By default, Jenkins performs branch indexing every 1 hour, but this interval can be configured in the Multibranch Pipeline settings.

beginner

Why is branch indexing important in Jenkins Multibranch Pipelines?

It ensures Jenkins automatically detects new branches and removes deleted ones, so builds stay up-to-date without manual job creation or deletion.

intermediate

What happens if branch scanning is disabled in Jenkins?

If branch scanning is disabled, Jenkins will not detect new or deleted branches automatically, requiring manual job management for branches.

What is the main purpose of branch indexing in Jenkins?

A To discover and manage branches automatically

B To build Docker images

C To deploy applications to production

D To monitor server health

Branch indexing helps Jenkins find all branches in the repository and manage jobs for them automatically.

How does Jenkins know when to update branch jobs in a Multibranch Pipeline?

A By checking disk space

B By manual user input only

C By monitoring CPU usage

D By performing branch scanning at set intervals

Jenkins uses branch scanning to check for new, changed, or deleted branches and updates jobs accordingly.

What happens if a branch is deleted in the repository but branch scanning is not run?

A Jenkins automatically deletes the job

B Jenkins crashes

C The Jenkins job for that branch remains until manually deleted

D The branch is restored in the repository

Without branch scanning, Jenkins does not detect deleted branches and their jobs remain until manually removed.

Which Jenkins feature automatically creates jobs for new branches?

A Branch indexing

B Build triggers

C Post-build actions

D Pipeline script

Branch indexing discovers new branches and creates jobs for them automatically.

Can the frequency of branch indexing be changed in Jenkins?

A Only by editing Jenkins core files

B Yes, it can be configured in the Multibranch Pipeline settings

C No, it is fixed and cannot be changed

D Only by reinstalling Jenkins

Jenkins allows configuring the interval for branch indexing in the Multibranch Pipeline job settings.

Explain how branch indexing and scanning help automate Jenkins Multibranch Pipelines.

Think about how Jenkins stays updated with changes in your source code branches.

Describe what could happen if branch scanning is disabled in a Jenkins Multibranch Pipeline project.

Consider the impact on automation and maintenance.

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