Setting Up CI Pipelines for Clojure Projects

14.6.1 Setting Up CI Pipelines for Clojure Projects

In the modern software development landscape, Continuous Integration (CI) is a critical practice that enables teams to deliver high-quality software efficiently. For Clojure developers, setting up a robust CI pipeline ensures that code changes are automatically tested, validated, and prepared for deployment. This section provides a comprehensive guide to setting up CI pipelines using popular services such as Jenkins, CircleCI, and GitHub Actions. We will cover running tests, code linting, and building artifacts, with practical examples and best practices.

Understanding Continuous Integration

Continuous Integration is a development practice where developers integrate code into a shared repository frequently, ideally several times a day. Each integration is verified by an automated build and tests, allowing teams to detect problems early.

Key Benefits of CI

• Early Bug Detection: Automated testing helps identify bugs early in the development cycle.
• Improved Code Quality: Consistent testing and code analysis improve the overall quality of the codebase.
• Faster Delivery: Automation speeds up the software delivery process, enabling faster releases.
• Reduced Integration Problems: Frequent integrations reduce the complexity of merging changes.

Setting Up CI with Jenkins

Jenkins is a widely used open-source automation server that supports building, deploying, and automating software development processes. It is highly customizable and supports a vast array of plugins.

Installing Jenkins

1. Download Jenkins: Visit the Jenkins website and download the latest stable version.
2. Install Jenkins: Follow the installation instructions for your operating system.
3. Start Jenkins: Run Jenkins and access it via http://localhost:8080.

Configuring Jenkins for Clojure

1. Install Plugins: Navigate to Manage Jenkins -> Manage Plugins and install the following plugins:

   • Git Plugin
   • Pipeline Plugin
   • Clojure Plugin (for syntax highlighting and build steps)

2. Create a New Job: Go to New Item, select Pipeline, and name your job.

3. Configure the Pipeline:

   • Source Code Management: Connect to your Git repository.
   • Pipeline Script: Use a Jenkinsfile to define your pipeline.

Example Jenkinsfile for Clojure

pipeline {
    agent any
    stages {
        stage('Checkout') {
            steps {
                git 'https://github.com/your-repo/clojure-project.git'
            }
        }
        stage('Build') {
            steps {
                sh 'lein deps'
            }
        }
        stage('Lint') {
            steps {
                sh 'lein cljfmt check'
            }
        }
        stage('Test') {
            steps {
                sh 'lein test'
            }
        }
        stage('Package') {
            steps {
                sh 'lein uberjar'
            }
        }
    }
    post {
        always {
            archiveArtifacts artifacts: '**/target/*.jar', fingerprint: true
        }
    }
}

Best Practices for Jenkins

• Use Declarative Pipelines: They are easier to read and maintain.
• Parallelize Stages: Run independent stages in parallel to speed up the pipeline.
• Use Docker: For consistent build environments, consider using Docker within Jenkins.

Setting Up CI with CircleCI

CircleCI is a cloud-based CI service that automates the software development process using continuous integration and delivery.

Configuring CircleCI for Clojure

1. Sign Up and Create a Project: Sign up on CircleCI and create a new project linked to your GitHub repository.

2. Add .circleci/config.yml: Create a configuration file in your repository to define the build process.

Example CircleCI Configuration

version: 2.1

executors:
  clojure-executor:
    docker:
      - image: circleci/clojure:lein-2.9.5

jobs:
  build:
    executor: clojure-executor
    steps:
      - checkout
      - run: lein deps
      - run: lein cljfmt check
      - run: lein test
      - run: lein uberjar
      - store_artifacts:
          path: target/uberjar
          destination: uberjar

workflows:
  version: 2
  build_and_test:
    jobs:
      - build

Best Practices for CircleCI

• Use Orbs: Reuse common configurations and commands using CircleCI Orbs.
• Optimize Caching: Cache dependencies to speed up builds.
• Parallel Jobs: Leverage CircleCI’s parallelism to run jobs concurrently.

Setting Up CI with GitHub Actions

GitHub Actions is a CI/CD service integrated directly into GitHub, allowing you to automate workflows directly from your repository.

Configuring GitHub Actions for Clojure

1. Create a Workflow: In your repository, navigate to Actions and set up a new workflow.

2. Define .github/workflows/ci.yml: Create a YAML file to define your CI pipeline.

Example GitHub Actions Workflow

name: CI

on:
  push:
    branches:
      - main
  pull_request:
    branches:
      - main

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
    - name: Checkout code
      uses: actions/checkout@v2

    - name: Set up JDK 11
      uses: actions/setup-java@v2
      with:
        java-version: '11'

    - name: Install Leiningen
      run: |
        curl https://raw.githubusercontent.com/technomancy/leiningen/stable/bin/lein > lein
        chmod a+x lein
        sudo mv lein /usr/local/bin/        

    - name: Install dependencies
      run: lein deps

    - name: Lint code
      run: lein cljfmt check

    - name: Run tests
      run: lein test

    - name: Build JAR
      run: lein uberjar

    - name: Upload artifact
      uses: actions/upload-artifact@v2
      with:
        name: uberjar
        path: target/uberjar/*.jar

Best Practices for GitHub Actions

• Reusable Workflows: Use reusable workflows to share common logic across repositories.
• Matrix Builds: Test against multiple environments using matrix strategies.
• Secrets Management: Securely manage sensitive data using GitHub Secrets.

Running Tests and Code Linting

Testing and code linting are integral parts of any CI pipeline. They ensure that code changes do not introduce regressions or violate coding standards.

Testing with lein test

Leiningen, the build tool for Clojure, provides a simple way to run tests using the lein test command. Ensure your test directory contains all necessary test files.

Code Linting with lein cljfmt

lein cljfmt is a Leiningen plugin for formatting Clojure code. It checks for code style issues and can automatically fix them.

;; project.clj
:plugins [[lein-cljfmt "0.6.8"]]

lein cljfmt check

Building Artifacts

Building artifacts is the final step in a CI pipeline, preparing the application for deployment.

Creating an Uberjar

An Uberjar is a standalone JAR file containing all dependencies. Use lein uberjar to create an Uberjar for your Clojure project.

lein uberjar

Conclusion

Setting up a CI pipeline for Clojure projects involves configuring automated processes to test, lint, and build your code. Whether you choose Jenkins, CircleCI, or GitHub Actions, the key is to automate repetitive tasks, ensuring consistent and reliable software delivery. By following the best practices outlined in this guide, you can establish a robust CI pipeline that enhances your development workflow.

Quiz Time!