What is continuous integration?

Continuous Integration (CI) is a practice in software development that encourages the frequent integration of code changes into a shared repository. This practice aims to increase efficiency, improve software quality, and maintain stability of production deployments. This guide will detail the concept of CI, its benefits, and its relationship with continuous delivery and continuous deployment.

What is continuous integration?

Continuous integration is the practice of automating the integration of code changes from multiple contributors into a single software project. It is a key DevOps practice that uses automated tools to build, package, and test applications automatically whenever there are new code changes.

Core principles of continuous integration

1. Automate the build and test process: Automation is crucial in CI to ensure that the integration process is consistent and repeatable.
2. Maintain a single source repository: All project code and dependencies should be stored in a version-controlled repository accessible to all team members.
3. Commit to the mainline frequently: Developers are encouraged to integrate their changes frequently, at least daily, to reduce integration conflicts.
4. Keep the build fast: Builds should be completed quickly to ensure that developers receive feedback quickly.
5. Test in a clone of the production environment: Testing in an environment that mirrors production as closely as possible ensures fewer surprises when deploying.
6. Make the latest production build accessible: Accessing the latest production build should be easy for team members, testers, and stakeholders.
7. Increase transparency: Transparency in the build results ensures that all team members can take immediate action when responding to incidents, and maintain context on the current state of the production deployment.

Relationship between CI and CD

Continuous delivery and continuous deployment are extensions of continuous integration, aimed at further increasing the speed and safety of software development and deployment.

Continuous delivery

Continuous delivery is the practice of ensuring that your codebase is always in a state that is ready to deploy. While CI focuses on the integration and testing phases, continuous delivery automates the release process so that you can deploy your application at any point with a single action. Unlike in continuous deployment, continuous delivery requires human intervention to trigger the final deployment to production.

Continuous deployment

Continuous deployment goes one step further than continuous delivery by automatically deploying every mainline change that passes the automated testing phase. This means there's no human intervention in the deployment process, and changes can go live minutes after being developed.

Implementing CI: best practices and tools

To implement CI effectively, you need the right tools and practices in place:

• Version control systems like Git allow developers to collaborate on code and track changes asynchronously.
• CI servers such as Jenkins, CircleCI, and GitHub Actions automate the build and test processes.
• Automated testing including unit tests, and integration tests, ensures that your production builds are stable before going live to users.

Example of setting up a CI process with GitHub Actions

Here’s a basic example of how you can set up a CI workflow using GitHub Actions:

name: CI

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

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v2
      - name: Setup Node.js
        uses: actions/setup-node@v2
        with:
          node-version: '14'

      - name: Install dependencies
        run: npm install

      - name: Run tests
        run: npm test

      - name: Build
        run: npm run build

This simple workflow configures GitHub Actions to run a build and test sequence every time changes are pushed to the main branch or a pull request is made to it.

Continuous integration when integrated with continuous delivery and continuous deployment, can significantly accelerate a development team’s ability to deliver applications quickly, reliably, and with confidence. By understanding and implementing CI, teams can ensure their development processes are more streamlined and less prone to error.