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CI/CD Pipeline - Hands-on

Jenkins based CI/CD Pipeline

Jenkins is an open-source continuous integration server for orchestrating the CI/CD pipelines. It supports integration with several components, infrastructure such as git, cloud etc. that helps in complete software development life cycle.

In this hands-on lab, let us: * Create a build pipeline (CI) for a simple java application. * Adding Test stage to build pipeline

This hands-on is based on the Jenkins running on docker on your local workstation, designed for Windows OS. For Linux OS, please follow the demo

Note: The hands-on lab is designed with Jenkins on the docker. However, the steps are applicable for the direct docker installation on your windows workstation as well.

Installing Git, Docker and Jenkins:

  • Install git command line tool on your workstation. (Follow this to install Git Locally·)
  • Docker Desktop for windows is installed on the workstation. Follow the instructions to install docker.
  • Ensure that your Docker for Windows installation is configured to run Linux Containers rather than Windows Containers. See the Docker documentation for instructions to switch to Linux containers.
  • Refer this to run and setup the Jenkins on docker.
  • Configure Jenkins with initial steps such as create an admin user etc. Follow Setup wizard.
  • If you have installed the Jenkins on your local workstation, make sure the maven tool is installed. Follow this to installl maven.

Forking Sample java application:

For this hands-on, let us fork a simple java application from the GitHub simple-java-maven-app. 1. Sign up for the GitHub account Join GitHub · GitHub. Once signed up, proceed to login. 2. Open the simple-java-maven-app by clicking on this link 3. On the top right corner, click on the ‘Fork’ to create a copy of the project to your GitHub account. (Refer Fork A Repo) 4. Once forked, clone this repository to your local workstation.

Create Jenkins Project:

  1. Login to the Jenkins portal at http://localhost:8080 using the admin account created earlier during Jenkins’s setup.
  2. On your first login, the following screen will appear. Click on “Create a Job”.

Fig 4: Jenkins - Create a Job

  1. On the next screen, type simple-java-pipeline in the Enter an Item Name field. Select Pipeline from the list of items and click OK.

Fig 5: Jenkins - Create Pipeline

  1. Click the Pipeline tab at the top of the page to scroll down to the Pipeline section.
  2. From the Definition field, choose the Pipeline script from SCM option. This option instructs Jenkins to obtain your Pipeline from Source Control Management (SCM), which will be your locally cloned Git repository.
  3. From the SCM field, choose Git.
  4. In the Repository URL field, specify the directory path of your locally cloned repository from the Forking Sample Java application section above.

Screen looks like below after entering the details.

Fig 6: Jenkins - Pipeline Configuration

Create Build pipeline using the Jenkinsfile:

Jenkinsfile is a script file containing the pipeline configuration and the stages and other instructions to Jenkins to create a pipeline from the file. This file will be saved at the root of the code repository. 1. Using your favorite text editor or IDE, create and save a new text file with the name Jenkinsfile at the root of your local simple-java-maven-app Git repository. 2. Copy the following declarative pipeline code and paste it into the empty Jenkinsfile. 

pipeline {
    agent {
        docker {
            image 'maven:3.8.1-adoptopenjdk-11' 
            args '-v /root/.m2:/root/.m2' 
        }
    }
    stages {
        stage('Build') { 
            steps {
                sh 'mvn -B -DskipTests clean package' 
            }
        }
    }
}

Note: If you are running Jenkins on your local workstation without the docker, please change the agent to any as shown below so that it runs on the localhost. Please ensure that the maven tool is installed on your local workstation.

pipeline {
    agent any

    stages {
        stage('Build') { 
            steps {
                sh 'mvn -B -DskipTests clean package' 
            }
        }
    }
}

In the above Jenkinsfile: * We specified an agent where the pipeline should run. 'docker’ in the agent section indicates to run a new docker container with the specified image. * In the stages section, we can define multiple steps as different stages. Here, we have a stage called ‘Build’, with the maven command for building the java application.

  1. Save your Jenkinsfile and commit and push to your forked repository. Run the following commands from the command prompt.
cd <your local simple-java-maven-app repo cloned folder>
git add .
git commit -m "Add initial Jenkinsfile"
git push origin master
  1. Go to Jenkins portal on your browser and click on the Dashboard. Open the simple-java-pipeline and from the left-menu, click on Build Now.

Fig 7: Jenkins - Building the Pipeline

  1. Notice the build running under the Build History menu. Click on the build number and it shows the stages.

Fig 8: Jenkins - View Running Builds

  1. We have successfully created a build pipeline with single stage and ran it. We can check the logs by clicking on the Console Output menu.

Additional stages in the build pipeline:

In the previous section, we have created the pipeline with a single stage. Typically, your CI pipeline contains multiple stages such as Build, Test and other optional stages such Code scanning etc. In this section, let us add a Test stage to the build pipeline and run.

  1. Go back to your text editor/IDE and open Jenkinsfile and the Test stage shown below.
stage('Test') {
            steps {
                sh 'mvn test'
            }
            post {
                always {
                    junit 'target/surefire-reports/*.xml'
                }
            }
        }

The Jenkinsfile looks like below after adding the Test stage.

pipeline {
    agent {
        docker {
            image 'maven:3.8.1-adoptopenjdk-11' 
            args '-v /root/.m2:/root/.m2' 
        }
    }
    stages {
        stage('Build') { 
            steps {
                sh 'mvn -B -DskipTests clean package' 
            }
        }
        stage('Test') {
            steps {
                sh 'mvn test'
            }
            post {
                always {
                    junit 'target/surefire-reports/*.xml'
                }
            }
        }
    }
}
  • Here the stage ‘Test’ is added which runs the maven command test.
  • The post -> always section ensures that this step is executed always after the steps are completed. The test report is available through Jenkins’s interface.

Note: If you are running Jenkins on your local workstation without the docker, please change the agent to any so that it runs on the localhost. Please ensure that the maven tool is installed on your local workstation.

pipeline {
    agent any

    stages {…

    }
}
  1. Save your Jenkinsfile and commit and push to your forked repository. Run the following commands from the command prompt.
cd <your local simple-java-maven-app repo cloned folder>
git add .
git commit -m "Test stage is added to Jenkinsfile"
git push origin master
  1. Go to Jenkins portal on your browser and click on the Dashboard. Open the simple-java-pipeline and from the left-menu, click on Build Now.
  2. Notice the Build and Test stages are showing in the Build screen.

Fig 9: Jenkins - Viewing the Running Builds with Test stage Included

We have now successfully created CI pipeline with two stages: Build and Test stages.