JenkinsPipeline-Jenkinsfile_Notes

Code Based pipeline
******************

Set up tools in global tool configuration:

 1. jdk ==> myjava
 2. maven ==> mymaven


Every job : common step

  SCM  ==> https://github.com/Sonal0409/DevOpsCodeDemo.git

Every job : maven command

Job1:
  maven command
 compile the code => compile

 connect job 1 with job2

Job2: Unit testing

 maven command
 test the code => test

 
 post build action:

    convert junit report

Connected to job 3

Job3: Code coverage

 maven command
 coverage the code => cobertura:cobertura -Dcobertura.report.format=xml

 
 post build action:

    convert coverage report ==> cobertura

Connected to job 4

Job4: package

 maven command
 package the code => package

Connected to job 5

Job5: Code review 

 maven command
 code review  => pmd:pmd

 
 post build action:

    convert pmd.xml report



We cna do all of this process in a signle by write code


With Jenkins 1 version : scripted pipeline syntax:

node{

was complex
jenkins admin has be really good in scripting because:

 > there is proper structure to the script
 > the entire script is as per the admin 
 > script are written in DSL which is groovy based 
 > when you executed the script, jenkisn doesnot validate the code at first
 > if the pieline stop in middle, you have start the pipeline again from the very step, which is time consuming


In jenkins 2 you will write the code using Declarative pipeline syntax

> write script for pipeline is very easy

> Declarative pipeline syntax is also groovy based and very easy to write

> Declarative pipeline syntax is well defiend and there is a structure/template that admin has to follow in order to write the code

> Jenkins provides a snippet generator tool, that automatically geenrates your pipeline code

> beacuse we define everything in a proper structure, its easy to read and easy to write.

> if you dont follow the structure given by jenkins, you will get error

> when you start exeucting the pipeline ==> 

   > jenkisn will validate the code give you errors

  > jenskin will exeucte the code

  > in case jenkisn pipeline stops in the middle, you can fix the issue and restart from that particular stage itself

> piepline is execution multiple stages/tasks 

  > these tasks can be executed in sequence or in parallel

> jenkisn can read or fetch the pipeline code form github and execute the pipeline --> Jenkinsfile


 Structure of writing Jenkins declarative syntax
****************************
  key 'value'

declarative syntax consist of various blocks

1. all the code will be placed inside the pipeline block
2. In the pipeline block you will create tools block, defining what tools to be used in the pipeline
 
 pipeline{

  tools{
     jdk 'myjava'
     maven 'mymaven'
}



agent any

stages{

   stage('Clone repo')
    {
      steps{
           
        git 'https://github.com/Sonal0409/DevOpsCodeDemo.git'

               }

    }

 stage('Compile the code')
    {
      steps{
           
      sh 'mvn compile'

               }

    }

 stage('Code Review')
    {
      steps{
           
      sh 'mvn pmd:pmd'

               }

    }


 stage('test the code')
    {
      steps{
       echo 'Testing'    
      sh 'mvn test'


               }
      
       post{

       success{
                    junit 'target/surefire-reports/*.xml'
               }
                }
    }

 stage('Coverage of the code')
    {
      steps{
        
      sh 'mvn cobertura:cobertura -Dcobertura.report.format=xml'


               }
      
       post{

       success{
                    cobertura autoUpdateHealth: false, autoUpdateStability: false, coberturaReportFile: 'target/site/cobertura/coverage.xml', conditionalCoverageTargets: '70, 0, 0', failUnhealthy: false, failUnstable: false, lineCoverageTargets: '80, 0, 0', maxNumberOfBuilds: 0, methodCoverageTargets: '80, 0, 0', onlyStable: false, sourceEncoding: 'ASCII', zoomCoverageChart: false
               }
                }
    }


 stage('Package the code')
    {
      steps{
           
      sh 'mvn package'

               }

    }

}
}


Jenkins file:
***************

Save the script in GITHUb - in a repo

> Jenkins to pick the script from github and run it 

   > go to the repo
   > cretae a new file with name as Jenkinsfile
   > In the file place your code

How will jenkisn pickup this code now?

   > create a job in jenkins -- template pipeline 

   > select option pipeline script from SCM
    > sCM - git

    > give repo path

press save
   

> Whenever there is an update on the script in github, this jenkins code should run automatically

       > set up a trigger on the job
       
       
 You can find the repo with jenkinsfile here:
 
 https://github.com/Sonal0409/DevOpsCodeDemo/blob/master/Jenkinsfile