Library directory structure in Jenkins - Mini Project: Build & Apply

Library Directory Structure in Jenkins

📖 Scenario: You are setting up a Jenkins shared library to reuse common pipeline code across multiple projects. This library will have a specific directory structure that Jenkins expects.

🎯 Goal: Build the basic directory structure for a Jenkins shared library with folders for vars and src, and add a simple Groovy script in vars.

📋 What You'll Learn

Create a root directory named my-shared-library

Inside it, create a vars directory

Inside vars, create a Groovy file named hello.groovy with a simple function

Create a src directory inside the root directory

💡 Why This Matters

🌍 Real World

Jenkins shared libraries help teams reuse pipeline code easily, making CI/CD pipelines cleaner and easier to maintain.

💼 Career

Understanding the Jenkins shared library structure is essential for DevOps engineers to create scalable and maintainable automation pipelines.

1

Create the root directory and vars folder

Create a directory named my-shared-library and inside it create another directory named vars.

Jenkins

# Your code here to create directories

Hint

Use commands like mkdir -p my-shared-library/vars to create nested directories.

2

Add a Groovy script in vars folder

Inside the vars directory, create a file named hello.groovy with this exact content:
def call() { echo 'Hello from shared library!' }

Jenkins

my-shared-library/
my-shared-library/vars/
# Create hello.groovy with the function inside vars

Hint

Use a text editor or echo command to create the file with the exact function.

3

Create the src directory

Inside the my-shared-library directory, create a directory named src.

Jenkins

my-shared-library/
my-shared-library/vars/hello.groovy
def call() { echo 'Hello from shared library!' }
# Create src directory inside my-shared-library

Hint

Use mkdir my-shared-library/src to create the src folder.

4

Display the directory structure

Use a command to display the full directory structure of my-shared-library showing vars/hello.groovy and src folders.

Jenkins

my-shared-library/
my-shared-library/vars/hello.groovy
def call() { echo 'Hello from shared library!' }
my-shared-library/src/
# Display directory tree

Hint

Use the tree command or ls -R to show the directory structure.

Practice

1. What is the primary purpose of the vars/ directory in a Jenkins shared library?

easy

A. To store simple Groovy scripts accessible as global variables

B. To store compiled Java classes

C. To hold configuration files like YAML or JSON

D. To keep pipeline job definitions

Solution

1. Step 1: Understand the role of vars/ directory

   The vars/ directory is used to store simple Groovy scripts that Jenkins loads as global variables or functions.

2. Step 2: Differentiate from other directories

   The src/ directory is for classes, and resources/ is for config files, so vars/ is specifically for simple scripts.

3. Final Answer:

   To store simple Groovy scripts accessible as global variables -> Option A

4. Quick Check:

   vars/ = simple scripts [OK]

Hint: Remember: vars = simple scripts, src = classes, resources = configs [OK]

Common Mistakes:

• Confusing vars/ with src/ directory
• Thinking vars/ holds config files
• Assuming vars/ stores compiled classes

2. Which directory should you place a Groovy class file named MyHelper.groovy in a Jenkins shared library?

easy

A. src/

B. vars/

C. resources/

D. jobs/

Solution

1. Step 1: Identify the purpose of src/ directory

   The src/ directory is meant for Groovy or Java classes in a Jenkins shared library.

2. Step 2: Match the file type to directory

   Since MyHelper.groovy is a class file, it belongs in src/, not vars/ or resources/.

3. Final Answer:

   src/ -> Option A

4. Quick Check:

   Classes go to src/ [OK]

Hint: Classes always go inside src/ folder [OK]

Common Mistakes:

• Placing class files in vars/
• Putting Groovy classes inside resources/
• Using non-existent jobs/ directory

3. Given this Jenkins shared library structure:
vars/notify.groovy
src/org/example/Helper.groovy
resources/config/settings.yml
Which file would you use to load configuration settings inside a pipeline?

medium

A. vars/notify.groovy

B. resources/config/settings.yml

C. vars/settings.yml

D. src/org/example/Helper.groovy

Solution

1. Step 1: Identify the purpose of resources/ directory

   The resources/ directory holds static files like configuration files (YAML, JSON) used by the library.

2. Step 2: Match the file type to usage

   Since settings.yml is a config file, it should be loaded from resources/config/settings.yml.

3. Final Answer:

   resources/config/settings.yml -> Option B

4. Quick Check:

   Config files = resources/ [OK]

Hint: Config files always go in resources/ [OK]

Common Mistakes:

• Trying to load config from vars/
• Confusing class files with config files
• Assuming config files go in src/

4. You placed a Groovy script build.groovy inside resources/ directory. What issue will you face when trying to call build() in your Jenkins pipeline?

medium

A. The script will run normally without issues

B. The script will be compiled but not executed

C. Jenkins will throw a missing method error because resources/ is for static files only

D. The pipeline will ignore the script and continue silently

Solution

1. Step 1: Understand the role of resources/ directory

   The resources/ directory is only for static files like configs, not executable Groovy scripts.

2. Step 2: Consequence of placing script in resources/

   Since build.groovy is not in vars/ or src/, Jenkins cannot load it as a callable method, causing a missing method error.

3. Final Answer:

   Jenkins will throw a missing method error because resources/ is for static files only -> Option C

4. Quick Check:

   Scripts must be in vars/ or src/ [OK]

Hint: Scripts in resources/ cause missing method errors [OK]

Common Mistakes:

• Expecting Groovy scripts to run from resources/
• Ignoring directory purpose and mixing files
• Assuming silent failure without error

5. You want to create a reusable Jenkins shared library that includes:
- A global function notifyBuild
- A helper class BuildHelper
- A configuration file email.yml
Which directory structure correctly organizes these files?

hard

A. src/notifyBuild.groovy, vars/BuildHelper.groovy, resources/email.yml

B. vars/notifyBuild.groovy, resources/BuildHelper.groovy, src/email.yml

C. resources/notifyBuild.groovy, src/BuildHelper.groovy, vars/email.yml

D. vars/notifyBuild.groovy, src/BuildHelper.groovy, resources/email.yml

Solution

1. Step 1: Assign global functions to vars/

   Global functions like notifyBuild go into vars/ as Groovy scripts.

2. Step 2: Place helper classes in src/

   Classes like BuildHelper belong in src/ directory.

3. Step 3: Store config files in resources/

   Configuration files such as email.yml must be inside resources/.

4. Final Answer:

   vars/notifyBuild.groovy, src/BuildHelper.groovy, resources/email.yml -> Option D

5. Quick Check:

   vars = functions, src = classes, resources = configs [OK]

Hint: Match file type: vars=func, src=class, resources=config [OK]

Common Mistakes:

• Swapping vars/ and src/ for functions and classes
• Placing config files outside resources/
• Mixing file types in wrong directories