Setting up a CI Pipeline with Jenkins and GitLab CI

Continuous Integration (CI) is a software development practice that allows developers to integrate code changes into a shared repository multiple times a day. This approach helps in detecting issues early, ensuring code quality, and streamlining the development process. Jenkins and GitLab CI are two popular tools used for setting up CI pipelines. In this blog post, we will guide you through the process of setting up a CI pipeline using Jenkins and GitLab CI in detail.

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Understanding Continuous Integration

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Before diving into the setup process, let’s briefly understand the concept of Continuous Integration. CI involves the following key practices:

1. Version Control System (VCS)

A robust version control system, such as Git, is essential for CI. Developers commit their changes to the repository multiple times a day, ensuring that the codebase is always up-to-date.

2. Automated Builds

Automated build tools compile the source code, run tests, and generate executable files or artifacts. This step ensures that the codebase can be successfully built without any manual intervention.

3. Automated Testing

Automated tests, including unit tests, integration tests, and acceptance tests, are executed automatically after each code commit. These tests help identify bugs and ensure that new changes do not break existing functionality.

4. Continuous Deployment

In addition to CI, Continuous Deployment (CD) involves automatically deploying code changes to production servers after passing all tests. However, in this blog post, we will focus on setting up CI using Jenkins and GitLab CI.

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Prerequisites

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Before diving into the setup, ensure you have the following prerequisites in place:

1. Git: A version control system for managing your source code.

2. GitLab: A Git repository hosting service where your codebase resides.

3. Jenkins: An automation server that will be responsible for running your CI pipeline.

4. Docker: (Optional) If you plan to use Docker for building and packaging your application.

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Setting up CI Pipeline with Jenkins

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Jenkins (https://www.jenkins.io/) is an open-source automation server widely used for CI and CD. Follow these steps to set up a basic CI pipeline with Jenkins:

Step 1: Install Jenkins

Install Java: Jenkins requires Java to run. Ensure that you have Java installed on your server or local machine.

Download Jenkins: Visit the [official Jenkins website](https://www.jenkins.io/download/) and download the appropriate version for your operating system.

Install Jenkins: Follow the installation instructions provided on the Jenkins website.

Step 2: Configure Jenkins

Access Jenkins: Once installed, access Jenkins through your web browser (typically at `http://localhost:8080`).

Install Plugins: Install necessary plugins for Git integration, build tools, and any other tools required for your projects.

Create a New Jenkins Job: Click on “New Item” to create a new Jenkins job. Choose the type of project you are working on (freestyle project, pipeline, etc.).

Configure Source Code Management: Select Git as your version control system and provide the repository URL and credentials if required.

Set Build Triggers: Configure build triggers, such as polling the repository for changes or triggering builds manually.

Configure Build Steps: Define build steps, such as compiling code, running tests, and generating artifacts.

Save and Run: Save your Jenkins job configuration and trigger the build to see if it runs successfully.

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Setting up CI Pipeline with GitLab CI

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GitLab CI (https://about.gitlab.com/stages-devops-lifecycle/continuous-integration/) is a part of GitLab, a web-based Git repository manager. It allows you to define and manage CI/CD pipelines directly within GitLab. Here’s how you can set up a CI pipeline with GitLab CI:

Step 1: Create a `.gitlab-ci.yml` file

Create a Repository: If you haven’t already, create a GitLab repository for your project.

Create `.gitlab-ci.yml`: Inside your repository, create a file named `.gitlab-ci.yml`. This file defines your CI/CD pipeline configuration.

Step 2: Define CI Pipeline Stages

stages:
  - build
  - test
  - deploy

Define the stages of your CI pipeline. In this example, there are three stages: `build`, `test`, and `deploy`.

Step 3: Configure Jobs for Each Stage

build:
  stage: build
  script:
    - echo "Building the project..."

test:
  stage: test
  script:
    - echo "Running tests..."

deploy:
  stage: deploy
  script:
    - echo "Deploying to production..."

Configure jobs for each stage. For example, the `build` job may compile your code, the `test` job may run tests, and the `deploy` job may deploy your application to a server.

Step 4: Commit and Push the `.gitlab-ci.yml` file

Commit and push the `.gitlab-ci.yml` file to your GitLab repository. GitLab CI will automatically detect the file and start running your CI pipeline based on the configuration you defined.

Setting up a CI pipeline is a fundamental practice in modern software development. Jenkins and GitLab CI are powerful tools that help automate the integration and testing process, leading to faster development cycles and higher code quality. By following the steps outlined in this guide, you can establish a robust CI pipeline for your projects, ensuring reliable and efficient software delivery.

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Happy Exploring!