Shared Libraries & Best Practices

Why shared libraries?

When many Jenkinsfiles copy the same “npm ci → test → docker build” block, extract it into a shared library.

Typical Git repo layout:

vars/
  buildNodeApp.groovy     # becomes step buildNodeApp()
src/
  org/mycompany/...       # Groovy classes
resources/
  ...                     # templates / non-Groovy files

vars/buildNodeApp.groovy

def call(Map config = [:]) {
    sh 'npm ci'
    sh 'npm test'
    sh 'npm run build'
}

Jenkinsfile

@Library('my-shared-library@main') _
 
pipeline {
    agent { docker { image 'node:20-alpine' } }
    stages {
        stage('Build') {
            steps {
                buildNodeApp()
            }
        }
    }
}

Configure the library under Manage Jenkins → System → Global Pipeline Libraries.

Production best practices

What you built across 4 days

Day 1  CI/CD + install + first job
Day 2  Freestyle + Git + triggers
Day 3  Declarative Jenkinsfile
Day 4  Docker agents + deploy + libraries