Shared-library

Jenkins Shared Library CI/CD Pipeline (Docker Project)

Overview

This project demonstrates how to use a Jenkins Shared Library to build a reusable CI/CD pipeline for a Docker-based application.

Instead of writing pipelines in every project, we centralize logic using a shared library.

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Objective

• Reuse pipeline code across projects
• Build Docker image from source code
• Push image to DockerHub
• Understand Jenkins Shared Library structure

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Architecture

GitHub Repo (App Code)
        ↓
Jenkins Pipeline
        ↓
Shared Library (Reusable Code)
        ↓
Docker Build & Push

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Repository Structure

🔹 Shared Library Repo

jenkins-shared-library/
│
├── vars/
│   ├── ciPipeline.groovy
│   ├── dockerBuild.groovy
│   ├── dockerPush.groovy
│   └── gitCheckout.groovy
│
└── src/
    └── com/devops/utils.groovy

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Jenkins Setup

1️⃣ Install Git on Jenkins Server

sudo yum install git -y  

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2️⃣ Configure Shared Library

Go to:

Manage Jenkins → Configure System → Global Pipeline Libraries

Add:

• Name: mind-lib

• Default Version: main

• SCM: Git

• Repository URL:

  https://github.com/jadalaramani/jenkins-shared-library.git
  

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3️⃣ Add DockerHub Credentials

Go to:

Manage Jenkins → Credentials

Add:

• Kind: Username with Password
• ID: dockerhub-cred
• Username: your DockerHub username
• Password: your DockerHub password

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Shared Library Code

🔹 gitCheckout.groovy

def call(String repoUrl, String branch='main') {
    git branch: branch, url: repoUrl
}

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🔹 dockerBuild.groovy

def call(String imageName, String tag) {
    sh "docker build -t ${imageName}:${tag} ."
}

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🔹 dockerPush.groovy

def call(String imageName, String tag, String credId) {

    withCredentials([usernamePassword(
        credentialsId: credId,
        usernameVariable: 'DOCKER_USER',
        passwordVariable: 'DOCKER_PASS'
    )]) {

        sh """
        echo "$DOCKER_PASS" | docker login -u "$DOCKER_USER" --password-stdin
        docker push ${imageName}:${tag}
        """
    }
}

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🔹 ciPipeline.groovy

def call(Map config) {

    def image = config.imageName

    pipeline {
        agent any

        environment {
            TAG = "${BUILD_NUMBER}"
        }

        stages {

            stage('Checkout') {
                steps {
                    gitCheckout(config.repoUrl)
                }
            }

            stage('Build Docker Image') {
                steps {
                    sh "docker build -t ${image}:${TAG} ."
                }
            }

            stage('Push Image') {
                steps {
                    dockerPush(image, TAG, config.dockerCred)
                }
            }

            stage('Deploy') {
                steps {
                    echo "Deploying ${image}:${TAG}"
                }
            }
        }
    }
}

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Jenkinsfile (Application Repo)

@Library('mind-lib') _

ciPipeline(
    repoUrl: 'https://github.com/jadalaramani/jenkins-shared-library.git',
    imageName: 'ramanijadalla/mindcircuit17d',
    dockerCred: 'dockerhub-cred'
)

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▶️ Pipeline Execution Flow

1. Jenkins pulls source code
2. Builds Docker image
3. Tags image with build number
4. Logs into DockerHub
5. Pushes image
6. Deploy stage runs

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Common Errors & Fixes

❌ Git not found

Install Git:

sudo yum install git -y

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❌ Credential type mismatch

Use:

usernamePassword (NOT string)

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❌ Environment variable error

Avoid:

IMAGE_NAME = config.imageName

Use:

def image = config.imageName

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Key Learnings

• Jenkins Shared Library structure
• Reusable pipeline design
• Secure credential handling
• Docker CI/CD workflow

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👨‍💻 Author

Jadala Ramani DevOps Engineer

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