What is Pipeline?
A pipeline refers to a series of automated steps and actions that define the continuous integration and continuous delivery (CI/CD) process for software development.
Jenkins pipelines are often defined within the version control system (Git) making it easy to manage changes to the pipeline itself.
A pipeline can execute multiple stages in parallel, improving efficiency.
Declarative
Declarative is a simplified and structured way to define Jenkins pipelines using a Domain-specific language (DSL).
Declarative is a more recent and advanced implementation of a pipeline as a code.
Declarative pipelines are defined using declarative blocks and include pre-defined sections for stages, steps and other pipeline elements.
Scripted
Scripted was the first and most traditional implementation of the pipeline as a code in Jenkins.
It was designed as a general-purpose DSL (Domain Specific Language) built with Groovy.
Why we should have a pipeline?
The definition of a Jenkins Pipeline is written into a text file (called a Jenkinsfile) which in turn can be committed to a project’s source control repository.
This is the foundation of "Pipeline-as-code"; treating the CD pipeline as a part of the application to be versioned and reviewed like any other code.
Creating a Jenkinsfile and committing it to source control provides several immediate benefits:
Automatically creates a Pipeline build process for all branches and pull requests.
Code review/iteration on the Pipeline (along with the remaining source code).
Pipeline Syntax
A pipeline is defined with a specific syntax known as groovy syntax. There's a proper way or method to write a pipeline. Out of the box method of the pipeline will cause an error during the deployment of an application.
Here's the proper syntax to write a pipeline:
pipeline {
agent any
stages {
stage('Build') {
steps {
//
}
}
stage('Test') {
steps {
//
}
}
stage('Deploy') {
steps {
//
}
}
}
}
Task 01
Create a New Job, this time select Pipeline instead of Freestyle Project.
Complete the example using the Declarative pipeline
steps:
Set up your Jenkins server as you did in the previous day's tasks.
Click on Create a new job on your Jenkins server.
Write the name of your job and select the pipeline instead of the freestyle project.
Write the description of your pipeline and select the GitHub project if it's from GitHub.
Go to the pipeline section and write the pipeline for your project. Write a simple pipeline for your understanding.
Then click on Save and Build Now to run your pipeline. The pipeline will be shown on your screen in real time.
This means that your pipeline and its groovy syntax running successfully. If any stage fails, the whole pipeline will fail from the failed step.
It's enough for today and your basic understanding of the pipeline. Practice to write the pipeline to make it perfect.
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