Shared Libraries
When multiple pipelines share the same logic (e.g., building a Docker image, sending Slack notifications), you can extract that code into a Shared Library. Shared Libraries are Groovy scripts stored in a Git repository and loaded by Jenkins.
Why Shared Libraries?
- DRY: Write once, use in many pipelines.
- Versioned: Libraries are versioned (Git tags).
- Encapsulate complex logic.
- Reduce Jenkinsfile size and complexity.
Structure of a Shared Library
A shared library requires a specific directory structure in a Git repo:
(root)
├── vars/
│ └── myStep.groovy # defines a global variable/step
└── src/ # optional, for Java-like classesExample: Create a Simple Step
In
vars/sayHello.groovy:def call(String name) {
echo "Hello, ${name}!"
}Configuring the Shared Library in Jenkins
1. "Manage Jenkins" → "Configure System" → "Global Pipeline Libraries".
2. Add a library with a name (e.g.,
my-lib).3. Set the Git repository URL and credentials.
4. Default version: can be a branch or tag (e.g.,
main).Using the Shared Library in a Pipeline
In your Jenkinsfile:
@Library('my-lib') _
pipeline {
agent any
stages {
stage('Hello') {
steps {
sayHello('Jenkins')
}
}
}
}Loading Libraries from Same Repo
You can also load a library from the same SCM as your Jenkinsfile using
library step:library identifier: 'my-lib@main', retriever: modernSCM([
$class: 'GitSCMSource',
remote: 'https://github.com/org/my-lib.git',
credentialsId: 'github-token'
])Best Practices
- Version your library (use Git tags).
- Keep steps small and focused.
- Document each step.
- Test library changes before rolling out.
Two Minute Drill
- Shared Libraries reuse pipeline code across many jobs.
- Structure:
vars/for global steps,src/for classes. - Configure in "Global Pipeline Libraries".
- Use
@Library('name') _to import.
Need more clarification?
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