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About Mary Zheng

Mary has graduated from Mechanical Engineering department at ShangHai JiaoTong University. She also holds a Master degree in Computer Science from Webster University. During her studies she has been involved with a large number of projects ranging from programming and software engineering. She works as a senior Software Engineer in the telecommunications sector where she acts as a leader and works with others to design, implement, and monitor the software solution.

Getting Started with Jenkins Pipeline

1. Introduction

Jenkins is an open-source automation server that enables developers to build, test, and deploy their software reliably. It has more than 1800 plugins. Jenkins Pipeline is a suite of plugins to support continuous delivery pipelines into Jenkins. In this example, I will demonstrate the following:

  • Install Jenkins and Pipeline plugin
  • Configure the maven tool
  • Build simple pipeline jobs to demonstrate with old node script and new declarative pipeline.

2. Technologies Used

The example code in this article was built and run using:

  • Jenkins 2.3
  • Docker Desktop
  • Github
  • Maven 3.6.1

3. Jenkins Installation

In this step, I will install Jenkins in a docker container on my Windows 10 PC.

  1. Create a folder –C:\MaryZheng\DevTools\Jenkins_home and share it via Docker setting ->Resource ->File Sharing.
  2. Pull docker image jenkins/jenkins:lts-jdk11 from Docker hub.
  3. Start the Jenkins container and map the volume to C:\MaryZheng\DevTools\Jenkins_home.
  4. Install suggested Jenkins plugins (pipeline, git, maven, etc).
  5. Create a “Hello World” Pipeline Job.

3.1 Docker File Sharing

This step is only needed when running Jenkins as a docker container at a windows PC.

Click docker Settings->Resources->File Sharing and click the “plus” icon to add a folder as a shared resource.

jenkins pipeline - docker resource
Figure 1 Docker Resource file Sharing

3.2 Pull Jenkins Docker Image

Create a Docker hub account if you don’t have one.

Execute docker pull command – docker pull jenkins/jenkins:lts-jdk11 to get the image.

docker pull jenkins/jenkins:lts-jdk11

PS C:\MaryZheng\DockerImages> docker pull jenkins/jenkins:lts-jdk11
lts-jdk11: Pulling from jenkins/jenkins
bb7d5a84853b: Pull complete                                                                                             3e2bcf6b1921: Pull complete                                                                                             978539702e19: Pull complete                                                                                             7fa18bcbf207: Pull complete                                                                                             a67725ef6531: Pull complete                                                                                             be5329269e0a: Pull complete                                                                                             f1514eafcdb2: Pull complete                                                                                             a1f0f8fcd02d: Pull complete                                                                                             8d76f0dde4b9: Pull complete                                                                                             9f47eedf727b: Pull complete                                                                                             74d1ec398ccc: Pull complete                                                                                             df71683f45f5: Pull complete                                                                                             95c82c721e5c: Pull complete                                                                                             2569d89b2015: Pull complete                                                                                             40a8b1ea9f1c: Pull complete                                                                                             4d4e70b7b6df: Pull complete                                                                                             d112a9446c9f: Pull complete                                                                                             Digest: sha256:510c7e5a5e62049e48f5d01cc6a5e03197f84fbbce70ea51d9d788043926180a
Status: Downloaded newer image for jenkins/jenkins:lts-jdk11
docker.io/jenkins/jenkins:lts-jdk11

3.3 Start Jenkins

Start the Jenkins from the docker run command.

docker run -p 9090:8080 -p 50000:50000 -v C:\MaryZheng\DevTools\Jenkins_home:/var/jenkins_home jenkins

PS C:\MaryZheng\DockerImages> docker run -p 9090:8080 -p 50000:50000  jenkins/jenkins:lts-jdk11                         Running from: /usr/share/jenkins/jenkins.war
webroot: EnvVars.masterEnvVars.get("JENKINS_HOME")
2021-11-04 22:58:58.605+0000 [id=1]     INFO    org.eclipse.jetty.util.log.Log#initialized: Logging initialized @1684ms to org.eclipse.jetty.util.log.JavaUtilLog
2021-11-04 22:58:58.812+0000 [id=1]     INFO    winstone.Logger#logInternal: Beginning extraction from war file
2021-11-04 22:59:00.671+0000 [id=1]     WARNING o.e.j.s.handler.ContextHandler#setContextPath: Empty contextPath
2021-11-04 22:59:00.858+0000 [id=1]     INFO    org.eclipse.jetty.server.Server#doStart: jetty-9.4.43.v20210629; built: 2021-06-30T11:07:22.254Z; git: 526006ecfa3af7f1a27ef3a288e2bef7ea9dd7e8; jvm 11.0.13+8
2021-11-04 22:59:01.608+0000 [id=1]     INFO    o.e.j.w.StandardDescriptorProcessor#visitServlet: NO JSP Support for /, did not find org.eclipse.jetty.jsp.JettyJspServlet
2021-11-04 22:59:01.729+0000 [id=1]     INFO    o.e.j.s.s.DefaultSessionIdManager#doStart: DefaultSessionIdManager workerName=node0
2021-11-04 22:59:01.730+0000 [id=1]     INFO    o.e.j.s.s.DefaultSessionIdManager#doStart: No SessionScavenger set, using defaults
2021-11-04 22:59:01.733+0000 [id=1]     INFO    o.e.j.server.session.HouseKeeper#startScavenging: node0 Scavenging every 660000ms
2021-11-04 22:59:02.860+0000 [id=1]     INFO    hudson.WebAppMain#contextInitialized: Jenkins home directory: /var/jenkins_home found at: EnvVars.masterEnvVars.get("JENKINS_HOME")
2021-11-04 22:59:03.179+0000 [id=1]     INFO    o.e.j.s.handler.ContextHandler#doStart: Started w.@639aba11{Jenkins v2.303.3,/,file:///var/jenkins_home/war/,AVAILABLE}{/var/jenkins_home/war}
2021-11-04 22:59:03.255+0000 [id=1]     INFO    o.e.j.server.AbstractConnector#doStart: Started ServerConnector@4189d70b{HTTP/1.1, (http/1.1)}{0.0.0.0:8080}
2021-11-04 22:59:03.257+0000 [id=1]     INFO    org.eclipse.jetty.server.Server#doStart: Started @6337ms
2021-11-04 22:59:03.261+0000 [id=23]    INFO    winstone.Logger#logInternal: Winstone Servlet Engine running: controlPort=disabled
2021-11-04 22:59:03.809+0000 [id=30]    INFO    jenkins.InitReactorRunner$1#onAttained: Started initialization
2021-11-04 22:59:03.887+0000 [id=28]    INFO    jenkins.InitReactorRunner$1#onAttained: Listed all plugins
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.google.inject.internal.cglib.core.$ReflectUtils$2 (file:/var/jenkins_home/war/WEB-INF/lib/guice-4.0.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int,java.security.ProtectionDomain)
WARNING: Please consider reporting this to the maintainers of com.google.inject.internal.cglib.core.$ReflectUtils$2
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2021-11-04 22:59:06.702+0000 [id=29]    INFO    jenkins.InitReactorRunner$1#onAttained: Prepared all plugins
2021-11-04 22:59:06.723+0000 [id=28]    INFO    jenkins.InitReactorRunner$1#onAttained: Started all plugins
2021-11-04 22:59:06.767+0000 [id=30]    INFO    jenkins.InitReactorRunner$1#onAttained: Augmented all extensions
2021-11-04 22:59:08.417+0000 [id=29]    INFO    jenkins.InitReactorRunner$1#onAttained: System config loaded
2021-11-04 22:59:08.418+0000 [id=29]    INFO    jenkins.InitReactorRunner$1#onAttained: System config adapted
2021-11-04 22:59:08.420+0000 [id=29]    INFO    jenkins.InitReactorRunner$1#onAttained: Loaded all jobs
2021-11-04 22:59:08.422+0000 [id=29]    INFO    jenkins.InitReactorRunner$1#onAttained: Configuration for all jobs updated
2021-11-04 22:59:08.505+0000 [id=44]    INFO    hudson.model.AsyncPeriodicWork#lambda$doRun$0: Started Download metadata
2021-11-04 22:59:08.529+0000 [id=44]    INFO    hudson.util.Retrier#start: Attempt #1 to do the action check updates server
2021-11-04 22:59:10.189+0000 [id=31]    INFO    jenkins.install.SetupWizard#init:

*************************************************************
*************************************************************
*************************************************************

Jenkins initial setup is required. An admin user has been created and a password generated.
Please use the following password to proceed to installation:

b9a0904907f34d6c85512f51245cff3e

This may also be found at: /var/jenkins_home/secrets/initialAdminPassword

Launch Jenkins at http://localhost:9090 and enter the initial password shown at line 41 to unlock Jenkins.

jenkins pipeline - unlock jenkins
Figure 2 Unlock Jenkins

Click the Continue button and set up an admin user. Now the Jenkins server is ready to use.

3.4 Installed Pipeline Plugin

In this step, I will install the suggested plugins via Jenkins Dashboard->Plugin Manager -> Manage Plugins menu. First, install the suggested plugins and then verify by viewing the “Installed” tab. Figure 3 shows the pipeline plugin is installed.

jenkins pipeline - pipeline plugin
Figure 3 Pipeline plugin is installed

3.5 Create a Hello World Pipeline

In this step, I will create a SimplePipelineJob from the provided “Hello World” script.

Click Dashboard ->New Item and enter “SimplePipelineJob“. Select “Pipeline” and click the OK button.

Figure 4 New SimplePipelineJob

Click the “Pipeline” tab and select the “Hello World” from the “Pipeline script” as shown at Figure 5. Click the “Save” button to create a pipeline job

Figure 5 Hello World Pipeline Job

Click the “Build Now” button and view the “Stages View“.

Figure 6 Hello World Stage View

4. Jenkins Pipeline Jobs

As you can see in the “Hello World” pipeline example, the step’s definition is captured by a groovy script. The stages and steps directives are required for a valid declarative Pipeline. In this step, I will create two pipeline jobs to clone source code from Github, build with maven, and test with JUnit.

4.1 Configure Maven Tool

Click Dashboard -> Manage Jenkins ->Global Tool Configuration ->Maven. Enter the maven361 for the Maven name. The maven name will be used in the pipeline scripts.

Figure 7 Configure Maven

4.2 Create a Scripted Pipeline

In this step, I will create a pipeline job with a choice input parameter. The input variable name is “BuildPara1“.

Figure 8 Input Parameter

Click the Pipeline tab and select the “Scripted Pipeline” option.

Figure 9 Scripted Pipeline

I will update the generated script for the following items:

  • Update the maven tool to “maven361” configured at the previous step.
  • Update the github URL to my testing URL
  • Add a new step to show the input choice value
  • Add a catch clause to accept an input to proceed or abort based on the user’s choice.

updated scripts

node {
    stage('Log parameter choices') {
        sh "echo 'INPUT is ${BuildPara1}' "
    }
    
    def mvnHome
    stage('Preparation') { // for display purposes
        // Get some code from a GitHub repository
        git 'https://github.com/maryzheng01/SinglePlayerPokerGame.git'
        // Get the Maven tool.
        // ** NOTE: This 'maven361' Maven tool must be configured
        // **       in the global configuration.
        mvnHome = tool 'maven361'
    }
    stage('Build') {
        // Run the maven build
        withEnv(["MVN_HOME=$mvnHome"]) {
            if (isUnix()) {
                try{
                    sh '"$MVN_HOME/bin/mvn" clean package'
                } catch (err) {
		    input 'maven clean package failed.  Verify in logs. Proceed to continue'
		}
            } else {
                bat(/"%MVN_HOME%\bin\mvn" -Dmaven.test.failure.ignore clean package/)
            }
        }
        
    }
    stage('Results') {
        junit '**/target/surefire-reports/TEST-*.xml'
        archiveArtifacts 'target/*.jar'
    }
}

Click the “Build with Parameter” button and click the Proceed or Abort button.

Figure 10 Interactive Job

4.3 Create a Declarative Pipeline

In this step, I will create a declarative pipeline with multiple steps.

declarative pipeline scripts

pipeline {
    agent any
    tools {
        maven 'maven361'
    }
    

    stages {
        
        stage('ENV Check') {
            steps {
               sh 'java --version'
            }
        }
        
        stage('GetResource') {
            steps {
               git 'https://github.com/maryzheng01/SinglePlayerPokerGame.git'
            }
        }
        
        stage('Build') {
            steps {
                echo "mvn"
                sh 'mvn -DskipTests clean install'
            }
        }
        
        stage('CleanUp') {
            steps {
               cleanWs()
            }
        }
         
    }
}

Click “Build Now” and view the results.

5. Summary

Jenkins Pipeline is used widely to support continuous integration and continuous deployment (CI/CD). In this example, I first installed Jenkins and Pipeline plugins. Then demonstrated with three Jenkins pipeline jobs:

  • Hello World Simple Pipeline.
  • Scripted Pipeline with an interactive user decision.
  • Declarative Pipeline with several steps.

6. Download the Source Code

Download
You can download the full source code of this example here: Getting Started with Jenkins Pipeline

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