DevOps classroom Series – 19/Feb/2021

Jenkins 2

• In this series we will look into the newer version of Jenkins feature that directly supports pipeline as a code
• Jenkinsfile:
  • In Jenkins 2 we can write our own pipeline defintion using a DSL (Domain Specific Language) and save it as a text file in our source code and Jenkins will read the pipeline from the scm (git) and execute the pipeline steps
  • This textfile is referred as Jenkinsfile. It is not necessary to name the file as Jenkinsfile, but it is a standard convention and many organizations using this standard.
• Jenkins supports two kinds of pipelines
  • Scripted Pipeline:
    • This is primarily a Groovy Script (Java Based Language)
  • Declarative Pipeline:
    • This was introduced by Cloud bees and this reduces the need to supplement the pipeline defintion with Groovy code to emulate traditional features of jenkins
• Jenkins 2 Supports some new project types
  • Pipeline
  • Folder
  • Organization
  • Multi branch pipeline

Foundations

• Scripted vs Declarative Pipeline
  • Scripted syntax refers to the intial way of pipeline as code in jenkins
  • Scripted Syntax is imperative style and is more dependend on Groovy language and Groovy constructs
  • Declarative syntax is the newer option
  • Pipelines are defined in a declarative style in clear sections that describe the states rather than focussing on logic
• Scripted Pipeline example

node('ltecomm') {
    stage('git'){
        git 'https://github.com/wakaleo/game-of-life.git'
    }
    stage('maven') {
        sh 'mvn clean package'
    }
    stage('archive artifacts') {
        archive 'gameoflife-web/targets/gameoflife.war'
    }
}

• Declarative Pipeline:

pipeline {
    agent { label 'ltecomm' }
    stages {
        stage('SCM') {
            steps {
                git 'https://github.com/wakaleo/game-of-life.git'
            }
        }
        stage('Build') {
            steps {
                sh 'mvn clean package'
            }
        }
    }
}

• Best way to configure pipeline is to create a Jenkinsfile in your source code

• Refer Here this changeset

• Now lets create a jenkins job

• Now lets change the Jenkinsfile to have the declarative pipeline Refer Here for the changes

• Basic Structure of Scripted pipeline

• Refer Here for the official docs

• Blue Ocean Interface:

  • Navigate to Jenkins Plugins and install Blue Ocean