As you embark on optimizing your development practices, you may come across the terms "continuous integration" (CI) and "continuous delivery" (CD) frequently. But what exactly is the difference between continuous integration vs continuous delivery?
I have helped numerous companies implement CI/CD pipelines over my 10+ years in test automation. In this comprehensive guide, I will demystify continuous integration and continuous delivery to help you leverage these practices for faster, better software delivery.
First, let‘s clarify the distinction at a high-level:
| Continuous Integration | Continuous Delivery | |
|---|---|---|
| Focus | Developer workflow | Release workflow |
| Goal | Catch defects early | Deploy to production rapidly |
| Stage | Build + test code | Release + deploy code |
| Automates | Code merges, builds, tests | Pipeline to production |
| Validate | Code changes | Releasability |
| Mindset | Code quality + velocity | Business agility |
Now let‘s explore each methodology more closely.
What is Continuous Integration?
Continuous integration (CI) is a development practice that focuses on improving code quality and development speed. It revolves around developers frequently merging code changes into a shared code repository multiple times per day. Common tools used for CI include Git, GitHub, Jenkins, CircleCI, TravisCI, and more.
The main goals of continuous integration include:
- Catch defects and integration issues early to enable faster remediation
- Maintain a stable, up-to-date codebase through frequent code merges
- Reduce lengthy merge conflicts by continually integrating code instead of long-lived feature branches
- Provide rapid feedback to developers when issues arise through test automation
By focusing on rapidly incorporating code and running automated checks (builds, tests) on each change, continuous integration shifts defect detection to the left in the development cycle. This means finding issues while code is still fresh in the developer‘s mind rather than right before major releases. Early validation reduces costs dramatically compared to later-stage bug fixes.
CI enables developers to code with more confidence since the system safeguards quality. Teams can thus accelerate velocity while improving software quality.
Core CI Practices
To implement continuous integration, teams standardize on practices like:
- Maintaining a shared code repository and branch (e.g. master) for ongoing integration
- Setting up automatic builds that compile code and package artifacts on a frequent basis (at least daily)
- Executing extensive automated testing suites against the latest build to catch regressions
- Providing rapid feedback loops for developers on build failures, test results, syntax issues, etc.
- Fixing integration issues immediately to maintain the code health and stability
By following core CI principles, teams establish a consistent, low-risk development workflow centered on quality.
What is Continuous Delivery?
Continuous delivery (CD) picks up where continuous integration ends and focuses on the optimal release and deployment of integrated code changes. The key metric is lead time: how fast a code change can safely progress from development to production.
CD introduces comprehensive release automation spanning build, testing, staging deployment, and final production deployment activities. The goal is to eliminate manual bottlenecks and quality gates that slow down delivery of customer value.
Benefits of implementing continuous delivery include:
- Faster innovation cycles through rapid iterations and incremental delivery of functionality
- Lower deployment risk through incremental changes rather than huge, batch releases
- Improved system stability from constant production-like testing
- Better developer productivity by reducing time spent on manual tasks
- Greater business agility to respond to changing market landscapes
CD provides the systems and process infrastructure for development teams to seamlessly progress working code to customers.
Core CD Practices
Common continuous delivery capabilities include:
- Fully scripted deployment processes that are repeatable, reliable and auditable
- Automated environment provisioning using Infrastructure-as-Code tools like Terraform
- Incremental updates delivered in smaller batches more frequently
- Extensive test automation across multiple environments to validate builds
- Easy and automated rollbacks to rapidly fix issues post-deployment
- Production-mirror testing environments that accurately replicate real-world conditions
- Dark launches and feature flags to test or target new functionality
While achieving end-to-end CD maturity takes time, teams can realize benefits through incremental automation. The end goal is maintaining releasable code that could ship to customers with minimal effort.
Key Differences Between CI and CD
While continuous integration and continuous delivery are complementary disciplines, they have some distinct differences:
Focus Area
- CI focuses on developer coding practices: integrating code, running builds, executing automated tests, code reviews, etc. Its sphere of control stays within the development team‘s context.
- CD focuses on release practices: taking integrated code through staging, testing, deployment, monitoring. It spans beyond development into IT/Ops territory.
Main Goal
- The goal of CI is detecting code defects and integration issues as early as possible in development. Feedback is directed at developers.
- The goal of CD is making sure integrated code changes are releasable and deployable to customers. Feedback looks at production-readiness.
Stage in Pipeline
- CI centers on the build and test phase. Code is integrated, constructed, and validated locally.
- CD revolves around the release and deploy phase. Code is packaged, deployed, tested in stage/prod environments.
Automation Focus
- CI automation includes enabling frequent code check-ins, builds, running automated test suites locally.
- CD automation encompasses the end-to-end pipeline – build, test, stage deployment, production deployment, etc.
Mindset Differences
- CI encourages a developer-centric mindset focused on code quality and velocity through test automation.
- CD drives a business-centric mindset focused on rapid production delivery to customers.
So in summary, CI supports developer effectiveness while CD improves business responsiveness. But together they enable acceleration of the entire software development lifecycle.
Implementing a CI/CD Pipeline
While CI and CD have distinct concerns, they work symbiotically to achieve comprehensive workflow automation from code check-in to production deployment.
Here are some tips on implementing robust CI/CD based on my experience:
Build a CI Foundation First
- Focus on optimizing the developer workflow through CI before expanding to downstream delivery automation.
- Master practices like trunk-based development, branch merging, automated building, and unit testing to validate code changes.
Prioritize Incrementally
- Resist the temptation to boil the ocean. Pick 1-2 friction points in your release process to eliminate first.
- Start small, demonstrate value, and expand automation efforts gradually over several releases.
Validate Early and Often
- Shift testing and validation to the left in your lifecycle by putting checks in place during development instead of right before release.
- Implement test automation to validate code functionality and quality early on while changes are still fresh. This reduces rework.
Monitor Pipeline Health
- Actively monitor DevOps metrics like lead time, deployment frequency, time to restore service, and change failure rate.
- Analyze metrics to continuously improve pipeline performance and catch issues.
Foster Cross-Team Collaboration
- Bring technology and business teams together early on to inform priorities and align on release timelines.
- Improve transparency between teams through information radiators like dashboards and broadcasts.
By judiciously combining CI and CD principles, you can optimize both developer productivity as well as business delivery speed. While the effort is non-trivial, CI/CD practices result in easier innovation, higher quality, and smooth releases over time.
Over 10+ years, I have helped numerous companies on their CI/CD journey – please reach out if you need any guidance!
