Jenkins Declarative Pipeline

1. What is a Pipeline?

A pipeline in Jenkins is a collection of steps or jobs that are interlinked in a sequence to automate the process of building, testing, and deploying software. Pipelines provide a robust way to manage continuous integration and continuous delivery (CI/CD) workflows, allowing teams to define complex processes in a simple, automated fashion.

2. Declarative Pipeline

The declarative pipeline is a more recent and advanced implementation of pipeline-as-code in Jenkins. It is structured, making it easier to read and write, especially for beginners or those who prefer a more formal syntax. The declarative pipeline is built with a specific syntax that simplifies the creation and management of pipelines by providing a clear structure with predefined sections and stages.

3. Scripted Pipeline

The scripted pipeline was the first and most traditional implementation of pipeline-as-code in Jenkins. It was designed as a general-purpose DSL (Domain Specific Language) built with Groovy. Although it offers more flexibility and control, it requires a deeper understanding of Groovy scripting and is less structured compared to the declarative pipeline.

Why You Should Use a Pipeline

The definition of a Jenkins Pipeline is written into a text file called a Jenkinsfile, which can be committed to a project’s source control repository. This is the foundation of "Pipeline-as-code," treating the CD pipeline as part of the application, which can be versioned and reviewed like any other code.

Creating a Jenkinsfile and committing it to source control provides several immediate benefits:

• Automatic Pipeline Creation: A pipeline build process is automatically created for all branches and pull requests, streamlining CI/CD workflows.

• Code Review and Iteration: The pipeline code can be reviewed and iterated along with the remaining source code, ensuring quality and consistency across the entire project.

Pipeline Syntax

Below is an example of a basic declarative pipeline syntax:

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                // Add build steps here
            }
        }
        stage('Test') {
            steps {
                // Add test steps here
            }
        }
        stage('Deploy') {
            steps {
                // Add deploy steps here
            }
        }
    }
}

This pipeline is divided into stages: Build, Test, and Deploy. Each stage contains steps that define the tasks to be executed.

Task: Creating a Jenkins Pipeline

Task-01: Create a New Job Using a Pipeline

1. Create a New Job: Start by creating a new job in Jenkins, selecting "Pipeline" instead of "Freestyle Project."

2. Follow the Official Jenkins "Hello World" Example: Jenkins provides an official "Hello World" example using a pipeline. You can follow this example to understand the basics of how pipelines work.

3. Complete the Example Using the Declarative Pipeline: Implement the example using the declarative pipeline syntax. This will help you get hands-on experience with the pipeline's structure and functionality.

By following these steps, you'll gain a solid understanding of Jenkins pipelines and how to integrate them into your CI/CD processes effectively.

Thank you for taking the time to read! 💚