Jenkinsfile Basics

1. Introduction

A Jenkinsfile is a text file that contains the definition of a Jenkins Pipeline. It is typically written in Groovy and is stored in the source control repository of the project, allowing for versioning and collaboration.

2. What is a Jenkinsfile?

Jenkinsfile is a way to define a Jenkins Pipeline as code. It allows you to specify how your CI/CD process should be executed, including build, test, and deployment stages.

3. Pipeline Structure

A Jenkins pipeline can be defined in two ways: declarative and scripted. The declarative syntax is simpler and recommended for most users.

3.1 Declarative Pipeline

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                // Build steps go here
            }
        }
        stage('Test') {
            steps {
                // Test steps go here
            }
        }
        stage('Deploy') {
            steps {
                // Deployment steps go here
            }
        }
    }
}

3.2 Scripted Pipeline

node {
    stage('Build') {
        // Build steps go here
    }
    stage('Test') {
        // Test steps go here
    }
    stage('Deploy') {
        // Deployment steps go here
    }
}

4. Stages and Steps

Each pipeline consists of stages that group related steps. Steps are the individual tasks that Jenkins performs, such as executing shell commands or running scripts.

Stages

• Define a sequence of operations.
• Can be parallelized.

Steps

• Individual commands or actions within a stage.
• Can include scripts, shell commands, or other plugins.

5. Example Jenkinsfile

Here’s a simple example of a Jenkinsfile that builds, tests, and deploys a Node.js application:

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                sh 'npm install'
            }
        }
        stage('Test') {
            steps {
                sh 'npm test'
            }
        }
        stage('Deploy') {
            steps {
                sh 'npm run deploy'
            }
        }
    }
}

6. Best Practices

• Keep Jenkinsfile simple and readable.
• Use descriptive stage names.
• Leverage environment variables for configuration.
• Version control your Jenkinsfile alongside your code.

7. FAQ