Continuous Integration (CI) is a fundamental practice in DevOps that involves automatically integrating code changes from multiple contributors into a shared repository several times a day. Setting up a CI pipeline ensures that code changes are automatically tested and validated, reducing integration issues and improving software quality.

1. Version Control System (VCS):

   • A VCS like Git is essential for tracking changes and collaborating on code.
   • Example: GitHub, GitLab, Bitbucket.

2. CI Server:

   • A CI server automates the process of building and testing code.
   • Example: Jenkins, Travis CI, CircleCI.

3. Build Automation:

   • Tools that compile code, run tests, and package applications.
   • Example: Maven, Gradle, npm.

4. Automated Testing:

   • Running tests automatically to ensure code quality.
   • Example: JUnit, Selenium, pytest.

Select a CI tool that fits your project needs. For this example, we will use Jenkins, a popular open-source CI tool.

1. Install Jenkins:

   • Download Jenkins from the official website and follow the installation instructions for your operating system.

2. Start Jenkins:

   • Run Jenkins and access the web interface at http://localhost:8080.

3. Initial Setup:

   • Unlock Jenkins using the initial admin password provided during installation.
   • Install suggested plugins to get started quickly.

1. Create a New Job:

   • Go to the Jenkins dashboard and click on "New Item."
   • Enter a name for your job and select "Freestyle project."

2. Configure Source Code Management:

   • Under "Source Code Management," select "Git."
   • Enter the repository URL and credentials if required.

3. Define Build Triggers:

   • Under "Build Triggers," select "Poll SCM" and set the schedule (e.g., H/5 * * * * to poll every 5 minutes).

4. Add Build Steps:

   • Under "Build," click "Add build step" and select "Execute shell" or "Invoke top-level Maven targets" based on your project.
   • Example shell script for a Node.js project:

     npm install
     npm test
     

1. Unit Tests:

   • Ensure your project includes unit tests. For example, in a Java project, you might use JUnit.
   • Example Maven configuration:

     <build>
       <plugins>
         <plugin>
           <groupId>org.apache.maven.plugins</groupId>
           <artifactId>maven-surefire-plugin</artifactId>
           <version>2.22.2</version>
         </plugin>
       </plugins>
     </build>
     

2. Integration Tests:

   • Include integration tests to validate the interaction between components.
   • Example shell script:

     mvn verify
     

1. Publish Test Results:

   • Under "Post-build Actions," select "Publish JUnit test result report."
   • Enter the path to the test result files (e.g., **/target/surefire-reports/*.xml).

2. Notifications:

   • Configure email notifications or integrate with chat tools like Slack to notify the team of build results.

For more advanced configurations, you can use Jenkins Pipeline (Jenkinsfile):

1. Install Jenkins on your local machine or use a cloud service.
2. Create a new Jenkins job for a sample project (e.g., a simple Java or Node.js application).
3. Configure the job to pull code from a Git repository.
4. Add build steps to compile the code and run tests.
5. Configure post-build actions to publish test results and send notifications.

1. Install Jenkins:

   • Follow the official Jenkins installation guide for your operating system.

2. Create a New Job:

   • Go to the Jenkins dashboard, click "New Item," enter a job name, and select "Freestyle project."

3. Configure Source Code Management:

   • Select "Git" and enter the repository URL.

4. Add Build Steps:

   • For a Node.js project:

     npm install
     npm test
     

5. Configure Post-Build Actions:

   • Select "Publish JUnit test result report" and enter the path to test results.

In this section, we covered the essential steps to set up a CI pipeline using Jenkins. We discussed the importance of version control, CI servers, build automation, and automated testing. By following the provided steps and example scripts, you can create a robust CI pipeline that ensures code quality and facilitates continuous integration. In the next module, we will delve into the fundamentals of Continuous Delivery (CD) and how it extends the CI process.