DevOps Classroom Series – 01/Oct/2020

Scripted Syntax vs Declarative Syntax

• Style:
  • Scripted syntax is imperative
  • Declrative Syntax is declarative
• Scripting:
  • Scripted: Uses Groovy lanugage constructs
  • Declarative: Jenkins DSL
• UI Tooling
  • Declarative: Blue Ocean
• Example:
  • Scripted:

    node('HMS') {
        stage ('git') {
            git 'https://github.com/dummygitrepos/gameoflife.git'
        }
        stage ('compile'){
            sh 'mvn package'
        }
    }
    

  • Declarative:

    pipeline {
        agent { label 'HMS' }
        stages {
            stage ('SCM') {
                steps {
                    git 'https://github.com/dummygitrepos/gameoflife.git'
                }
            },
            stage ('Compile') {
                steps {
                    sh 'mvn package'
                }
            } 
        }
    }
    

Scripted Syntax

• node: This line tells jenkins on which node it should run this part of pipeline
  • syntax:
    • node(‘HMS’)
    • node (‘HMS && QA’)
  • Then node will have a closure {}
• stage:
  • This is also a closure will allows to run the steps
  • Should have a name.
• steps:
  • Jenkins DSL Commands are referred as steps.
  • This is lowest/atomic level of functionality defined by the DSL.
  • Refer Here for all the available steps
  • Now lets look at git steps and understand different ways of defining a step
    • Navigate to git the above link
    • Refer the docs from here
    • Every step has arguments
    • Different versions of git step

    1. git 'https://github.com/dummygitrepos/gameoflife.git'
    2. git url: 'https://github.com/dummygitrepos/gameoflife.git', branch: 'master'
    

• Relation b/w node stage and steps are as shown below

Declarative Pipeline Structure

• The Structure is represented below
• Refer Here for declarative pipeline
• Agents in pipeline: Refer Here
  • Example syntax

    pipeline {
        agent { label 'HRMS && QA'  }
    }