CI/CD pipelines are the backbone of modern software development practices, enabling teams to automate the processes of building, testing, and deploying applications. A well-designed pipeline ensures that code changes are consistently integrated and deployed, reducing the risk of errors and increasing the speed of delivery.

• Source Stage: The pipeline is triggered by a change in the source code repository.
• Build Stage: The application is compiled, and dependencies are resolved.
• Test Stage: Automated tests are run to ensure code quality.
• Deploy Stage: The application is deployed to a staging or production environment.
• Monitor Stage: The deployed application is monitored for performance and errors.

• Define the pipeline using code, often in YAML or JSON format.
• Store the pipeline configuration in the same repository as the application code.

• Parallel Execution: Multiple jobs or stages run simultaneously to save time.
• Sequential Execution: Jobs or stages run one after another, ensuring dependencies are met.

• Intermediate or final products generated during the pipeline (e.g., compiled binaries, Docker images).

• Events that start the pipeline, such as code commits, pull requests, or scheduled times.

Let's look at a simple CI/CD pipeline example using YAML syntax, which is common in tools like GitLab CI/CD and Jenkins.

• Stages: Defines the different stages of the pipeline.
• build_job: A job in the build stage that runs the build.sh script and saves the build artifacts.
• test_job: A job in the test stage that runs the run_tests.sh script.
• deploy_job: A job in the deploy stage that runs the deploy.sh script, but only if the code is on the master branch.

Objective: Create a basic CI/CD pipeline that builds, tests, and deploys a simple application.

Steps:

1. Set Up the Repository:

   • Create a new repository on GitHub or GitLab.
   • Add a simple application (e.g., a "Hello World" script).

2. Define the Pipeline:

   • Create a .gitlab-ci.yml file (for GitLab) or a Jenkinsfile (for Jenkins) in the root of the repository.
   • Define the stages and jobs as shown in the example above.

3. Implement Build Script:

   • Create a build.sh script that compiles or prepares the application.

4. Implement Test Script:

   • Create a run_tests.sh script that runs basic tests on the application.

5. Implement Deploy Script:

   • Create a deploy.sh script that deploys the application to a staging environment.

6. Commit and Push:

   • Commit the changes and push them to the repository.
   • Observe the pipeline execution in the CI/CD tool's interface.

Here is a sample solution for a GitLab CI/CD pipeline:

• Missing Dependencies: Ensure all necessary dependencies are installed in the build environment.
• Incorrect Paths: Double-check file paths in scripts and artifact definitions.
• Pipeline Triggers: Make sure the pipeline is correctly triggered by the desired events (e.g., commits to specific branches).

CI/CD pipelines are essential for automating the software development lifecycle, ensuring consistent and reliable delivery of applications. By understanding the key concepts and practicing with real examples, you can design and implement effective pipelines for your projects. In the next module, we will delve deeper into dependency management within CI/CD pipelines.