GitLab CI vs. Jenkins

1. Overview

Choosing the right Continuous Integration/Continuous Deployment (CI/CD) tool is important for streamlining development and deployment processes in software development. Two prominent tools in this space are GitLab CI and Jenkins. They offer powerful features for automating builds, tests, and deployments. However, they both cater to different needs and preferences.

Knowing the differences between GitLab CI and Jenkins can help us select the most suitable tool for our project requirements.

In this tutorial, we’ll explore the features of GitLab CI and Jenkins. Additionally, we’ll compare their capabilities to provide a comprehensive understanding of their strengths and differences.

2. GitLab CI

GitLab CI integrates seamlessly with GitLab, making it a popular web-based DevOps lifecycle tool. As a CI/CD tool, developers can automate building, testing, and code deployment.

Let’s break down the features of GitLab CI that make it stand out for CI/CD.

2.1. Version Control Integration

GitLab CI is tightly integrated with GitLab’s version control system. This integration simplifies the setup process since the CI/CD functionality is built into the same platform that hosts the code repository. With this in place, we can easily create and manage CI/CD pipelines directly from GitLab repositories.

For example, let’s consider a simple pipeline definition using GitLab CI configuration:

stages:
  - build
  - test

build_job:
  stage: build
  script:
    - echo "Compiling the code..."
    - gcc -o my_app my_app.c

test_job:
  stage: test
  script:
    - echo "Running tests..."
    - ./my_app --run-tests

We have configured a pipeline with two stages: build and test. The build_job compiles the code, while the test_job runs the test. This example demonstrates the seamless integration of GitLab CI with GitLab’s version control system. This ensures seamless and automated execution with every code commit.

2.2. Auto DevOps

It also offers Auto DevOps, a feature that automatically detects, builds, tests, deploys, and monitors applications based on best practices. In particular, it simplifies the CI/CD process by providing pre-configured CI/CD pipelines that work out of the box.

2.3. Container Registry

GitLab CI includes a built-in container registry. This feature allows us to build, store, and deploy Docker images seamlessly. Additionally, this integration makes it easier to manage Docker images and use them within CI/CD pipelines.

For example, let’s look at a pipeline that builds and deploys a Docker image:

stages:
  - build
  - deploy

build_job:
  stage: build
  script:
    - docker build -t my-app:latest .
    - docker login -u $CI_REGISTRY_USER -p $CI_REGISTRY_PASSWORD $CI_REGISTRY
    - docker push $CI_REGISTRY/my-group/my-project/my-app:latest

deploy_job:
  stage: deploy
  script:
    - docker pull $CI_REGISTRY/my-group/my-project/my-app:latest
    - docker run -d -p 80:80 my-app:latest

From the configuration setup, the pipeline builds a Docker image, pushes it to the GitLab container registry, and then deploys it.

2.4. GitLab Runners

GitLab CI uses runners to execute jobs. Runners are lightweight, agent-like processes that run the scripts defined in the .gitlab-ci.yml file. Furthermore, they can be shared with a project enhancing flexibility in managing build environments.

For example, let’s consider a job that requires a specific runner:

stages:
  - test

test_job:
  stage: test
  script:
    - npm install
    - npm test
  tags:
    - docker

In this example, the job runs on a runner tagged with docker, ensuring it has the necessary environment.

2.5. Pipeline Visibility

GitLab CI offers robust pipeline visualization tools. Furthermore, we can easily view the status of each stage and job, see logs, and identify any failures. This feature enhances quick diagnoses and issue resolution:

For example, the GitLab CI/CD dashboard (source) provides a graphical representation of different pipelines, showing the progress and results of each stage.

2.6. Security and Compliance

In software development, security and compliance are important. GitLab CI offers out-of-the-box security scanning and compliance. It can automatically scan code for vulnerabilities and enforce compliance with security policies. It ensures applications adhere to best practices.

For example, let’s consider a pipeline that includes a security scanning stage:

include:
  - template: Security/SAST.gitlab-ci.yml

stages:
  - test
  - security

sast:
  stage: security

In the configuration, this pipeline uses GitLab’s Static Application Security Testing (SAST) template to scan for security vulnerabilities as part of the CI/CD process.

3. Jenkins

Jenkins is a widely used open-source automation server. Just like GitLab CI, we can build, test, and deploy applications. As a standalone CI/CD tool, Jenkins is highly extensible through its vast ecosystem of plugins. In particular, it allows customizations to fit specific needs. Additionally, it’s known for flexibility and robust functionalities, which support a wide range of software development workflows.

Let’s break down the features of Jenkins that make it a powerful tool for CI/CD.

3.1. Extensive Plugin Ecosystem

It’s one of Jenkins’s powerful features. Jenkins boasts over 1,500 plugins that extend its capabilities. The plugins integrate with various version control systems to deploy applications to different environments.

For example, let’s consider a pipeline that uses plugins for Git integration and Docker build:

pipeline {
    agent any
    stages {
        stage('Checkout') {
            steps {
                git 'https://github.com/example/repo.git'
            }
        }
        stage('Build Docker Image') {
            steps {
                script {
                    docker.build('my-app:latest')
                }
            }
        }
    }
}

In the configuration, the pipeline uses the Git plugin to check the code and the Docker plugin to build a Docker image.

3.2. Declarative and Scripted Pipelines

These are the types of pipelines offered by Jenkins. Declarative pipelines provide a simpler and more structured way to define CI/CD pipelines using a predefined syntax. Additionally, scripted pipelines are more flexible and controlled through Groovy scripts.

For example, let’s consider a simple declarative pipeline:

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                echo 'Building...'
                sh 'make build'
            }
        }
        stage('Test') {
            steps {
                echo 'Testing...'
                sh 'make test'
            }
        }
    }
}

The example illustrates the use of a declarative pipeline with two stages: Build and Test. From the pipeline, the structure is straightforward to read. Therefore, it makes it accessible for users with different levels of expertise.

3.3. Blue Ocean Interface

Jenkins provides the Blue Ocean Plugin. Additionally, this plugin offers a modern and user-friendly interface for creating, visualizing, and managing pipelines.

In particular, the feature simplifies pipeline creation with a visual editor and enhances pipeline visualization with intuitive graphical representations.

3.4. Pipeline as a Code

Jenkins promotes pipeline as a code functionality. In particular, pipelines are defined and versioned using code stored in the project repository.

For example, a Jenkinsfile store in the repository defines the pipeline configuration:

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                echo 'Building...'
                sh 'make build'
            }
        }
        stage('Test') {
            steps {
                echo 'Testing...'
                sh 'make test'
            }
        }
    }
}

Committing this Jenkinsfile to the repository ensures the pipeline configuration is consistent and traceable.

3.5. Distributed Builds

Jenkins supports distributed builds across multiple machines. By using Jenkins agents, jobs can be distributed to different nodes, allowing parallel execution and faster build times.

For example, let’s consider a Jenkinsfile that specifies different agents for different stages:

pipeline {
    agent none
    stages {
        stage('Build') {
            agent { label 'build-node' }
            steps {
                echo 'Building on build-node...'
                sh 'make build'
            }
        }
        stage('Test') {
            agent { label 'test-node' }
            steps {
                echo 'Testing on test-node...'
                sh 'make test'
            }
        }
    }
}

The build stage of this configuration runs on a node labeled build-node, while the test stage runs on a node labeled test-node, demonstrating Jenkins’ ability to distribute tasks.

3.6. Community Support

Jenkins is an open-source project with numerous plugin ecosystems. Additionally, professional developers and engineers contribute to and support these plugins through community efforts.

4. Comparisons Between GitLab CI and Jenkins

Here are some comparisons between GitLab CI and Jenkins:

5. Conclusion

In this article, we’ve explored the features and capabilities of both GitLab CI and Jenkins. Furthermore, by understanding their strengths and differences, we can decide which CI/CD tool best suits our project needs.

Finally, the choice between GitLab CI and Jenkins depends on specific requirements, ease of integration, and the desired level of customization.