🧱 Lecture 11: Continuous Integration and Continuous Deployment (CI/CD) with Jenkins

Farrukh Rehman
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Previous lesson: 🧱 Lecture 10 : Dockerizing the Full Stack Application

🎯 Introduction

In modern software development, manual builds and deployments are no longer sustainable. Teams need speed, reliability, and consistency. This is exactly what Continuous Integration (CI) and Continuous Deployment (CD) provide.

Jenkins is one of the most powerful tools for implementing CI/CD. It enables teams to automate everything from code integration to production deployment.

In this lecture, you will learn:

What CI/CD really means in practice
How Jenkins works
How to write pipelines using Jenkinsfile
How to automate build, test, and deployment
Best practices used in professional teams
This is a practical, industry-aligned guide.

What is Continuous Integration (CI)?

Continuous Integration is the practice of frequently merging code into a shared repository and automatically validating every change.

A typical CI workflow:

Developer pushes code to GitHub
Pipeline automatically triggers
Application builds
Tests run
Feedback is provided immediately

Why CI Matters

Bugs are caught early
Integration conflicts are reduced
Code quality improves
Teams ship faster with confidence

Without CI, teams often discover problems too late — during release.

What is Continuous Deployment (CD)?

Continuous Deployment goes one step further.

After code passes:

Build
Tests
Quality checks

…it is automatically deployed to environments like staging or production.

Some teams use:

Continuous Delivery → Deployment requires manual approval
Continuous Deployment → Deployment is fully automatic

Both models are common in professional environments.

What is Jenkins?

Jenkins is an open-source automation server that allows you to build complete CI/CD pipelines.

With Jenkins, you can:

Pull code from repositories
Build applications
Run automated tests
Perform static code analysis
Deploy applications
Trigger workflows across tools

Jenkins is popular because:

It is free and open-source
It supports thousands of plugins
It works with almost any tech stack
It scales from small teams to large enterprises

Jenkins Architecture (Simplified)

Jenkins typically consists of:

Jenkins Controller (Master)

Manages jobs
Provides UI
Schedules pipelines
Handles configuration

Jenkins Agents (Workers)

Execute the actual builds
Can run on separate machines
Useful for scaling pipelines

Pipelines

Define the automation workflow
Written as code using a Jenkinsfile

Lets Write our Jenkinsfile

for backend .net application

pipeline {
    agent any
     options {
        disableConcurrentBuilds()
    }   
    stages {
        stage('Build') {
            steps {
                script {
                    // Remove previous image with the <none> tag  testing
                    sh 'docker rmi ecom-backend:latest || true'

                    // Build the new image with an explicit tag  
                    sh 'docker build --no-cache -t ecom-backend:latest -f ECommerce.API/Dockerfile .'

                    // Remove dangling images
                    sh 'docker images -q --filter "dangling=true" | xargs docker rmi || true'

                    // Clean up intermediate images
                    sh 'docker image prune -f'

                    // Custom cleanup script to remove any remaining <none> tagged images
                    sh '''
                        for image_id in $(docker images --filter "dangling=true" -q); do
                            docker rmi $image_id || true
                        done
                    '''
                }
            }
        }
        stage('Push and Deploy') {
            steps {                
                script {
                    // Stop and remove the container if it exists
                    sh 'docker stop ecom-backend || true'
                    sh 'docker rm ecom-backend || true'

                    // Run the new container
                    sh 'docker run -d --restart always --name ecom-backend --env "ASPNETCORE_ENVIRONMENT=Development" --network zohan -p 8202:8080 ecom-backend:latest'

                     sh 'docker image prune -f'
                }
            }
        }
    }
}

Lets Write for Frontend

pipeline {
    agent any
     options {
        disableConcurrentBuilds()
    }   
    stages {       

        stage('Build') {
            steps {
                sh 'docker build --no-cache -t ecom-front/ui -f Dockerfile .'
            }
        }
        stage('Push and Deploy') {
            steps {                
                sh 'docker stop ecom-front || true && docker rm ecom-front || true'
                sh 'docker run -d --restart always --name ecom-front --network zohan -p 9201:80 ecom-front/ui:latest'

            }
        }
    }
}