Multiple SCM repositories in Jenkins - Mini Project: Build & Apply

Managing Multiple SCM Repositories in Jenkins Pipeline

📖 Scenario: You are working on a Jenkins pipeline that needs to pull code from two different Git repositories. This is common when your project depends on multiple codebases that must be built or tested together.

🎯 Goal: Build a Jenkins pipeline script that checks out two separate Git repositories into different directories within the workspace.

📋 What You'll Learn

Use the checkout step to clone Git repositories

Clone the first repository into the default directory

Clone the second repository into a subdirectory named repo2

Use exact repository URLs: https://github.com/example/repo1.git and https://github.com/example/repo2.git

Print a message confirming both repositories are checked out

💡 Why This Matters

🌍 Real World

Many projects depend on multiple code repositories. Jenkins pipelines often need to pull code from several sources to build and test combined projects.

💼 Career

Knowing how to manage multiple SCM repositories in Jenkins is a key skill for DevOps engineers and CI/CD pipeline developers.

1

Setup first Git repository checkout

Create a Jenkins pipeline script that uses the checkout step to clone the Git repository from https://github.com/example/repo1.git into the default workspace directory.

Jenkins

// Your code here to checkout the first Git repository

Hint

Use the checkout step with GitSCM class and specify the repository URL exactly.

2

Add second Git repository checkout with custom directory

Add a second checkout step to clone the Git repository from https://github.com/example/repo2.git into a subdirectory named repo2 inside the workspace. Use the dir step to specify the directory.

Jenkins

pipeline {
    agent any
    stages {
        stage('Checkout Repo1') {
            steps {
                checkout([$class: 'GitSCM', branches: [[name: '*/main']], userRemoteConfigs: [[url: 'https://github.com/example/repo1.git']]])
            }
        }
        stage('Checkout Repo2') {
            steps {
                // Your code here to checkout the second Git repository into 'repo2'
            }
        }
    }
}

Hint

Use the dir('repo2') step to change directory before checking out the second repository.

3

Add a stage to verify both repositories are checked out

Add a new stage named Verify Checkout that uses the sh step to run the shell command ls -l in the workspace root and inside the repo2 directory to list files and confirm both repositories are present.

Jenkins

pipeline {
    agent any
    stages {
        stage('Checkout Repo1') {
            steps {
                checkout([$class: 'GitSCM', branches: [[name: '*/main']], userRemoteConfigs: [[url: 'https://github.com/example/repo1.git']]])
            }
        }
        stage('Checkout Repo2') {
            steps {
                dir('repo2') {
                    checkout([$class: 'GitSCM', branches: [[name: '*/main']], userRemoteConfigs: [[url: 'https://github.com/example/repo2.git']]])
                }
            }
        }
        stage('Verify Checkout') {
            steps {
                // Your code here to list files in workspace and repo2
            }
        }
    }
}

Hint

Use multiple sh steps to run ls -l commands in the root and repo2 directories.

4

Print confirmation message after checkout verification

Add a final step in the Verify Checkout stage that prints the message "Both repositories have been checked out successfully." using the echo step.

Jenkins

pipeline {
    agent any
    stages {
        stage('Checkout Repo1') {
            steps {
                checkout([$class: 'GitSCM', branches: [[name: '*/main']], userRemoteConfigs: [[url: 'https://github.com/example/repo1.git']]])
            }
        }
        stage('Checkout Repo2') {
            steps {
                dir('repo2') {
                    checkout([$class: 'GitSCM', branches: [[name: '*/main']], userRemoteConfigs: [[url: 'https://github.com/example/repo2.git']]])
                }
            }
        }
        stage('Verify Checkout') {
            steps {
                sh 'echo "Files in workspace root:"'
                sh 'ls -l'
                sh 'echo "Files in repo2 directory:"'
                sh 'ls -l repo2'
                // Your code here to print confirmation message
            }
        }
    }
}

Hint

Use the echo step to print the confirmation message exactly as given.

Practice

1.

What is the main benefit of using multiple SCM repositories in a Jenkins job?

easy

A. It allows Jenkins to fetch code from several repositories in one build.

B. It speeds up the Jenkins server performance automatically.

C. It merges all repositories into a single repository permanently.

D. It restricts Jenkins to use only one branch per build.

Solution

1. Step 1: Understand Jenkins SCM usage

   Jenkins uses SCM to get source code for building projects.

2. Step 2: Identify multiple SCM benefit

   Multiple SCM lets Jenkins pull from many repositories in one job, useful for projects with dependencies.

3. Final Answer:

   It allows Jenkins to fetch code from several repositories in one build. -> Option A

4. Quick Check:

   Multiple SCM = fetch multiple repos [OK]

Hint: Multiple SCM means multiple code sources in one job [OK]

Common Mistakes:

• Thinking it merges repos permanently
• Assuming it improves server speed
• Believing it limits branches

2.

Which Jenkins pipeline syntax correctly defines two SCM repositories using checkout steps?

<pre>1) checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo1.git']]]) checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo2.git']]]) 2) checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo1.git', url: 'https://repo2.git']]]) 3) checkout([$class: 'GitSCM', url: 'https://repo1.git']) checkout([$class: 'GitSCM', url: 'https://repo2.git']) 4) checkout([$class: 'GitSCM', userRemoteConfigs: ['https://repo1.git', 'https://repo2.git']])

easy

A. Option 1

B. Option 2

C. Option 3

D. Option 4

Solution

1. Step 1: Check syntax for multiple SCM in Jenkins pipeline

   Each checkout step handles one SCM repo; multiple repos require multiple checkout calls.

2. Step 2: Analyze options

   Option 1 uses two separate checkout calls with correct userRemoteConfigs. Option 2 tries to combine repos in one config incorrectly. Option 3 uses wrong key url directly. Option 4 uses wrong list format.

3. Final Answer:

   Option 1 -> Option A

4. Quick Check:

   Separate checkout per repo = Option 1 [OK]

Hint: Use separate checkout steps for each repo [OK]

Common Mistakes:

• Combining multiple URLs in one userRemoteConfigs entry
• Using 'url' key instead of userRemoteConfigs
• Passing URLs as plain list without map

3.

Given this Jenkins pipeline snippet, what will be the result?

stage('Checkout') {
  steps {
    checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo1.git']]])
    checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo2.git']]])
  }
}

Choose the correct statement about the workspace after this stage runs.

medium

A. The workspace contains code from both repo1 and repo2 in separate folders.

B. The workspace contains only repo2 code, repo1 is overwritten.

C. The workspace contains merged files from repo1 and repo2 in the root folder.

D. The build will fail due to multiple checkout commands.

Solution

1. Step 1: Understand default checkout behavior

   By default, Jenkins checks out each repo into the same workspace folder, overwriting previous content.

2. Step 2: Analyze the effect of two checkout calls

   The second checkout replaces the first repo's files because both use the root workspace folder without specifying subdirectories.

3. Final Answer:

   The workspace contains only repo2 code, repo1 is overwritten. -> Option B

4. Quick Check:

   Multiple checkout without directories overwrites workspace [OK]

Hint: Without directories, last checkout overwrites workspace [OK]

Common Mistakes:

• Assuming repos merge automatically
• Thinking Jenkins creates subfolders by default
• Believing multiple checkouts cause build failure

4.

In a Jenkins job configured with multiple SCM repositories, the build fails with this error: hudson.plugins.git.GitException: Command "git clone" failed. What is the most likely cause?

medium

A. The workspace directory is not cleaned before checkout.

B. The Jenkins server has no internet connection.

C. The Jenkinsfile syntax is invalid.

D. The userRemoteConfigs list is empty or missing URLs.

Solution

1. Step 1: Understand the error context

   Git clone failure usually means the repository URL is invalid or missing.

2. Step 2: Check multiple SCM config

   If userRemoteConfigs is empty or missing URLs, Jenkins cannot clone repos, causing this error.

3. Final Answer:

   The userRemoteConfigs list is empty or missing URLs. -> Option D

4. Quick Check:

   Missing repo URLs cause git clone failure [OK]

Hint: Check repo URLs in userRemoteConfigs first [OK]

Common Mistakes:

• Blaming workspace cleanup for git clone errors
• Assuming Jenkinsfile syntax causes git clone failure
• Ignoring network issues as cause

5.

You want to configure a Jenkins pipeline to checkout two Git repositories into separate folders repo1 and repo2 inside the workspace. Which pipeline snippet correctly achieves this?

checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo1.git']], extensions: [[$class: 'RelativeTargetDirectory', relativeTargetDir: 'repo1']]])
checkout([$class: 'GitSCM', userRemoteConfigs: [[url: 'https://repo2.git']], extensions: [[$class: 'RelativeTargetDirectory', relativeTargetDir: 'repo2']]])

hard

A. This snippet merges both repos into the root workspace folder.

B. This snippet will fail because RelativeTargetDirectory is not supported.

C. This snippet correctly checks out both repos into separate folders.

D. This snippet only checks out the first repo; second is ignored.

Solution

1. Step 1: Understand RelativeTargetDirectory extension

   This extension tells Jenkins to checkout the repo into a specified subfolder inside the workspace.

2. Step 2: Analyze the snippet

   Each checkout uses RelativeTargetDirectory with different folder names, so repos go into separate folders without overwriting.

3. Final Answer:

   This snippet correctly checks out both repos into separate folders. -> Option C

4. Quick Check:

   RelativeTargetDirectory separates repos in workspace [OK]

Hint: Use RelativeTargetDirectory to separate repos in workspace [OK]

Common Mistakes:

• Not using RelativeTargetDirectory causes overwriting
• Assuming Jenkins merges repos automatically
• Believing second checkout is ignored