In this blog, I will discuss the Jenkins Pipeline and the types of pipelines: Declarative and Scripted Pipelines.

Let’s start!

1. Jenkins Pipeline

According to the official documentation of Jenkins, “ Jenkins Pipeline is a suite of plugins that supports implementing and integrating continuous delivery pipelines into Jenkins. “

Pipelines allow for defining a series of steps that will be executed whenever the change of code like building, testing, and deploying takes place.

Pipelines enable modeling simple-to-complex delivery Pipelines as a Code. The definition of a Jenkins Pipeline is written into a text file called Jenkinsfile.

Jenkins Pipelines are written in a domain-specific language (DSL) called Declarative Pipeline. This DSL makes it easy to define complex pipelines without writing a lot of code.

2. Why Pipelines?

• They are easy to use.

• They are scalable.

• They are flexible.

• They are secure.

• Automate the software development process.

• Improve the quality of your code.

• Increase the speed of your deployments.

• Improve collaboration.

3. Pipeline Concepts

3.1 Pipeline

A Pipeline is a user-defined model of a CD pipeline. This is a vital part of Declarative Pipeline Syntax.

3.2 Node

A node is a machine part of the Jenkins environment and capable of executing a Pipeline. This is a key part of Scripted Pipeline Syntax.

3.3 Stage

A stage in a pipeline is a logical grouping of steps that are executed together. Stages are typically used to group related tasks, such as building, testing, and deploying code.

3.4 Step

A step in a pipeline is a single action that is executed as part of a stage. Steps are typically used to perform tasks such as building, testing, and deploying code.

Now let us know the types of Pipelines. There are two types: Declarative Pipelines and Scripted Pipelines.

4. Declarative Pipeline

Declarative Pipeline is based on a set of declarative statements that define the structure and behavior of your pipeline. These statements are grouped into sections, which are executed in order.
Declarative Pipeline is a new syntax for writing Jenkins Pipelines. It is designed to be more concise and easier to read than the Scripted Pipeline syntax.

4.1 Syntax

pipeline {
    agent any #1
    stages {
        stage('Build') { #2
            steps {
                //#3
            }
        }
        stage('Test') { #4
            steps {
                //#5
            }
        }
        stage('Deploy') { #6
            steps {
                //#7
            }
        }
    }
}

#1 Execute this Pipeline or any of its stages, on any available agent.

#2 Defines the “Build” stage.

#3 Perform some steps related to the “Build” stage.

#4 Defines the “Test” stage.

#5 Perform some steps related to the “Test” stage.

#6 Defines the “Deploy” stage.

#7 Perform some steps related to the “Deploy” stage.

5. Scripted Pipeline

Scripted Pipeline is based on a Groovy script that defines the structure and behavior of the pipeline. The script is executed in order, and it can contain a variety of steps, including building, testing, and deploying code.
Scripted Pipeline is a syntax for writing Jenkins Pipelines. It is the original syntax for Pipelines, and it is still supported in Jenkins.

5.1 Syntax

node { #1
    stage('Build') { #2
        //#3
    }
    stage('Test') { #4
        // #5
    }
    stage('Deploy') { #6
        // #7
    }
}

#1 Execute this Pipeline or any of its stages, on any available agent.

#2 Defines the “Build” stage. ‘stage’ blocks are optional in Scripted Pipeline syntax.

#3 Perform some steps related to the “Build” stage.

#4 Defines the “Test” stage.

#5 Perform some steps related to the “Test” stage.

#6 Defines the “Deploy” stage.

#7 Perform some steps related to the “Deploy” stage.

6. Difference between Declarative and Scripted Pipelines

7. Jenkinsfile

A Jenkinsfile is a text file that contains the definition of a Jenkins Pipeline. It is typically stored in the root directory of the project that it is used to automate.

The following is an example of a Jenkinsfile:

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        sh 'mvn clean install'
      }
    }
    stage('Deploy') {
      steps {
        sh 'scp -r target/*.jar localhost:/opt/app'
      }
    }
  }
}

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.

Now let us complete tasks as we now know the basics of the Pipelines.