Creating CI/CD pipelines in Jenkins

Introduction

One of the revolutionary practices transforming modern software development is Continuous Integration and Continuous Deployment (CI/CD) for delivering high-quality software quickly and efficiently. Organizations use CI/CD to deliver a product faster and to detect bugs early in the software lifecycle.

Jenkins is a popular open -source automation server built in Java . It plays a pivotal role in automating these processes. In this blog post, we'll understand how to create a Jenkins pipeline, from setting up your Jenkins environment to deploying your application.

What is Jenkins?

Jenkins is an open-source automation server that enables developers to build, test, and deploy their code with ease. Jenkins supports a wide range of plugins, allowing integration with any tool in your CI/CD . Jenkins pipelines allow you to define your build, test, and deployment processes making them versionable and reusable across projects.

Prerequisites

Before delving into creating a Jenkins pipeline, we should ensure we have the following : ·        Jenkins installed and operational on your server or local machine.

·        Basic understanding of Jenkins and CI/CD concepts.

·        A version control system (such as Git) containing your project's code.

Setting Up Jenkins

1.     Install Jenkins:

·        Download and install Jenkins from the official Jenkins Website.

·        Follow the installation instructions specific to your operating system.

2.     Install Required Plugins:

·        Navigate to Manage Jenkins > Manage Plugins.

·        Install the following essential plugins: Pipeline, Git, GitHub, Docker (if using Docker).

Types of pipeline

There are two types of Jenkins pipeline code.

--> Declarative Pipeline

--> Scripted Pipeline

In this blog, let's dive into the details of Declarative Pipelines, explore their features, and learn how to create a sample pipeline."

Declarative Pipeline

A Declarative Pipeline is a type of pipeline syntax in Jenkins that allows you to define your entire CI/CD process in a clear, structured, and easy-to-read format using a predefined DSL (Domain Specific Language). It simplifies the pipeline creation process and is recommended for most users due to its readability and straightforward syntax.

Features of Declarative Pipeline:

1. Simplified Syntax: The Declarative Pipeline uses a more straightforward and user-friendly syntax compared to the Scripted Pipeline, making it easier to write and understand.

2. Pipeline as Code: Like all Jenkins pipelines, a Declarative Pipeline is defined in code, allowing you to version control your build, test, and deployment configurations along with your application code.

3. Structured Blocks: It uses predefined blocks such as pipeline, agent, stages, and steps to define the different parts of your CI/CD process. This structured approach enforces best practices and reduces complexity.

4. Built-in Error Handling: Includes constructs for handling errors and defining post-execution actions, such as post blocks for success, failure, and always scenarios.

5. Extensibility: Easily extendable with Jenkins plugins to support various tools and services within the CI/CD pipeline.

6. Parallel Execution: Supports parallel execution of stages, allowing multiple tasks to be run simultaneously, which can significantly reduce pipeline execution time.

Example of a Declarative Pipeline

Here's a simple example of a Declarative Pipeline:

Create a New Jenkins :

• From the Jenkins dashboard, click on New Item.

• Enter a name for your job and select Pipeline as the project type.

• Click OK to create the job.

• Select all required general configurations if any .

• In pipeline tab under script enter the following code,
  

Explanation of the Pipeline Script

• pipeline: This block is the root block of the Jenkins pipeline and encapsulates the entire pipeline configuration.

•        agent any: This specifies that the pipeline can run on any available Jenkins agent.

•        stages: This block defines the different stages of your pipeline. Each stage consists of steps that define the actions to be performed.

•        stage('Checkout'): Checks out the code from your Git repository.

•        stage('Build'): Builds your project (e.g., compiles the code).

•        stage('Test'): Runs tests on your project.

•        stage('Deploy'): Deploys your application.

•        post: This block defines actions to be performed after the pipeline execution, such as sending notifications.

Running Your Pipeline

1.     Save Your Pipeline:

•      Save your pipeline script in the Jenkins job configuration.

•      Click Save.

2.     Run the Pipeline:

•     Click Build Now to trigger the pipeline.

•     Monitor the console output to track the progress of each stage.

The pipeline script is a sample and the code can be customized according to the project requirements.

Advantages of Declarative Pipelines

1.  Readability: The high-level, structured syntax of Declarative Pipelines makes them easy to read and understand. This improves collaboration among team members and simplifies the onboarding process for new developers.

2.    Ease of Use: The simplified syntax and predefined structure reduce the complexity of writing and maintaining pipelines, making it accessible to a broader range of users, including those who may not be familiar with Groovy scripting.

3.    Consistency: Declarative Pipelines enforce a consistent approach to pipeline definition, which helps maintain standards and best practices across different projects and teams.

4.    Maintainability: Due to their clear and concise structure, Declarative Pipelines are easier to maintain. Changes can be made with minimal risk of introducing errors.

5.  Error Handling: Built-in mechanisms for handling errors and defining post-execution actions help ensure pipelines are robust and can gracefully handle failures.

6.    Modularity: Pipelines can be modularized using shared libraries and reusable blocks, promoting code reuse and reducing duplication.

7.   Integration: Since the pipeline is defined in code, it can be stored in a version control system (e.g., Git), allowing for versioning, branching, and collaboration.

8.    Flexibility: While enforcing a structured approach, Declarative Pipelines still offer enough flexibility to cater to complex CI/CD workflows, including parallel execution and conditional stages.

Conclusion

Creating a Jenkins pipeline is a powerful way to automate your CI/CD processes, ensuring that your software is always in a deployable state. By following the steps outlined in this blog post, you can set up and customize your Jenkins pipelines to fit your specific project needs. Experiment with different stages, steps, and advanced features to fully leverage Jenkins' capabilities.