Basic DevOps CI/CD Pipeline #2

Before reading this blog, check out the first part of the series.

In this part, we’ll integrate a private GitHub repository with Jenkins by adding credentials and automate the process of building and pushing Docker images.

Adding GitHub Credentials to Jenkins

1. Access Jenkins GUI:

   • Navigate to your Jenkins instance in a web browser.

2. Add Credentials:

   • Go to Manage Jenkins > Credentials > (Global) > Add Credentials.
   • Select “Username with password” as the kind.
   • Fill in your GitHub username and password.
   • Assign an ID to these credentials, e.g., github-creds.
   • Click “OK” to save.

   You should now see the credentials listed.

Creating the Jenkins Pipeline

We’ll create a Jenkins pipeline to check out the source code from GitHub.

1. Create a New Pipeline:

   • In Jenkins, create a new pipeline job.

2. Define the Pipeline Script:

   • Use the following script to check out the code:

     pipeline {
         agent any
         stages {
             stage('Checkout') {
                 steps {
                     git(branch: 'master', credentialsId: 'github-creds', url: 'https://github.com/github_user/private-repository.git')
                 }
             }
         }
     }
     

   Replace github_user/private-repository.git with your repository’s URL.

Preparing the Application

We’ll use a basic Maven Spring Boot web application project. You can create one at start.spring.io, selecting version 2.4.1 and Java 8.

Adding a Dockerfile

Create a Dockerfile in your project with the following content:

FROM openjdk:8-jdk-alpine
COPY . /data
WORKDIR /data
RUN ["mvn", "clean", "install"]
COPY target/*.jar ./app.jar
ENTRYPOINT ["java", "-Xmx750m", "-jar", "app.jar"]

Setting Up DockerHub

1. Create a DockerHub Account:

   • Sign up at hub.docker.com.

2. Add DockerHub Credentials to Jenkins:

   • In Jenkins, go to Manage Jenkins > Credentials > (Global) > Add Credentials.
   • Select “Username with password” as the kind.
   • Enter your DockerHub username and password.
   • Assign an ID, e.g., dockerhub-creds.
   • Click “OK” to save.

Docker Operations in Jenkinsfile

We’ll use Jenkins plugins to interact with Docker:

1. Install Required Plugins:

   • Ensure the following plugins are installed:
     • Pipeline
     • Docker
     • Docker Pipeline

   Install them via Manage Jenkins > Manage Plugins > Available tab.

2. Define Build and Push Stages:

   • Update your Jenkinsfile with the following stages:

     pipeline {
         agent any
         stages {
             stage('Checkout') {
                 steps {
                     git(branch: 'master', credentialsId: 'github-creds', url: 'https://github.com/github_user/private-repository.git')
                 }
             }
             stage('Build') {
                 steps {
                     script {
                         newImage = docker.build 'yourdockerhubuser/javaapp'
                     }
                 }
             }
             stage('Push') {
                 steps {
                     script {
                         docker.withRegistry('', 'dockerhub-creds') {
                             newImage.push("${env.BUILD_NUMBER}")
                         }
                     }
                 }
             }
         }
     }
     

   Replace yourdockerhubuser with your DockerHub username.

   • Build Stage:

     • Builds the Docker image with the tag yourdockerhubuser/javaapp.

   • Push Stage:

     • Logs in to DockerHub using the provided credentials.
     • Tags the image with the current Jenkins build number.
     • Pushes the image to DockerHub.

Next Steps

In the next episode, we will continue by preparing a deployment Ansible playbook, triggering the playbook within Jenkins, and setting up the monitoring baseline.

Stay tuned!