Lecture Notes on Jenkins and CI/CD Automation

Overview of Jenkins

• Jenkins is an automation server used to build projects.
• It acts as a CI (Continuous Integration) tool and a CD (Continuous Delivery/Deployment) tool.
• Jenkins orchestrates the whole CI/CD flow.
• Can integrate with tools like Argo CD for microservices deployment and Ansible for software deployment.
• Can trigger automated tests after compiling source code.

Artifacts in CI/CD

• Artifacts refer to the output of build processes, like compiled binaries or executables.
• Example formats: .exe for Windows, .jar (Java Archive) for Java, .war (Web Application Archive) for Java web applications.
• Artifacts include compiled source code and dependencies and can be stored in artifact repositories like Nexus.
• Important for storing different versions to allow rollback if newer versions fail.

Jenkins CI/CD Workflow

• Code is developed and pushed to a version control system like GitHub.
• Jenkins monitors the repository for changes using a GitHub webhook or SCM polling.
• Upon detecting changes, Jenkins performs a build, creates artifacts, and can deploy these to a server.
• Artifacts are stored in repositories such as Nexus for version control.

Configuring Jenkins

• Jenkins can be set up to pull changes from a repository periodically using SCM polling.
• Build triggers can be set up using CRON expressions to define polling frequency.

Introduction to Maven

• Maven is a build tool used primarily for Java projects.
• It utilizes a Project Object Model (POM) for configuration, listing dependencies, and repositories.
• Maven's POM file is central to its operation, detailing project structure, dependencies, and plugins.
• Maven automatically handles library dependencies and can be integrated into Jenkins pipelines.

Using Jenkins with Maven

• Jenkins pipelines can invoke Maven to handle the build stage of the CI/CD pipeline.
• Pipelines can be staged, such as Build, Test, Deploy, with each stage handling specific tasks.
• Jenkins can trigger Maven and other tools like JUnit for running tests.

Repository and Version Control

• Version control for Jenkins pipelines is better managed in source control systems like GitHub.
• Storing Jenkinsfiles in a repo allows for better collaboration and versioning.

Issues and Troubleshooting

• Errors in Jenkins builds might be due to misconfigured roles, permissions, or missing dependencies.
• Common issues include Terraform not being found or incorrect IAM roles in AWS.

Practical Tips

• Always ensure Jenkins is correctly configured to pull from the right branches and repositories.
• Use CRON jobs for scheduled builds but ensure the correct syntax is used.
• When debugging Jenkins, examine console outputs for detailed error logs.
• Utilize Jenkins’ plugin ecosystem to extend its capabilities.