CI vs CD: Differences, Similarities, and Best Practices
Continuous Integration (CI) and Continuous Delivery (CD) are two practices at the core of modern software development. They are interconnected, yet distinct, approaches that aim to streamline and expedite software development and delivery.
- CI and CD are similar in that they both focus on automation, frequent code changes, and a commitment to maintaining a high-quality, releasable codebase.
- CD is different from CI in the sense that CI focuses on preparing code for release (build/test) and CD involves the actual release of code (release/deploy).
CI is all about integrating and testing code changes frequently to maintain stability and early problem detection. It facilitates collaborative environments, catching integration issues at nascent stages, and expedites release cycles. CI is the watchful sentinel ensuring a stable, high-quality code base through an automated build system.
CD, on the other hand, picks up where CI leaves off, extending the process into the realm of automated deployment. It ensures that software is always in a production-ready state, thus promoting rapid, reliable deployments. CD is like a conductor, orchestrating the flow of the software release process from the beginning to the final production deployment.
This is part of a series of articles about CI/CD.
What Is Continuous Integration (CI)?
Continuous Integration (CI) is an essential practice in modern software development that focuses on integrating code changes from multiple developers into a shared repository as frequently as possible. This practice ensures that the code base remains stable, and any issues are discovered and resolved as early as possible in the development lifecycle.
CI plays a vital role in maintaining the quality and stability of software projects. By regularly integrating code changes, developers can identify integration issues or bugs early in the development process. This early detection allows teams to resolve these problems before they escalate, saving time and resources.
How CI works
CI relies on an automated build system to compile and test the code whenever a developer pushes their changes to the shared repository. Upon detecting an integration issue or a failed test, the build system notifies the responsible developer, who can then address the problem. This immediate feedback loop helps maintain a stable and high-quality code base.
Advantages of continuous integration
Implementing CI in your software development process has numerous benefits:
- Early detection of issues: By integrating and testing code changes frequently, CI allows the development team to identify and resolve issues early in the development process.
- Improved collaboration: CI fosters a collaborative environment where developers work together on a shared codebase, reducing the risk of conflicts and improving overall teamwork.
- Faster release cycles: CI ensures that the code is always in a releasable state, making it easier to deploy new features and bug fixes quickly.
What Is Continuous Delivery (CD)?
Continuous Delivery (CD) is an extension of Continuous Integration that focuses on automating the entire software release process, from code changes to deployment in production. CD ensures that the software is always in a releasable state, allowing development teams to deploy new features and bug fixes quickly and reliably.
CD is crucial in today’s fast-paced software development landscape because it enables teams to deliver high-quality software at a rapid pace. By automating the release process, CD minimizes human error and ensures that software is always production-ready.
How CD works
CD builds upon CI by automating the deployment process. Once the code passes all tests and checks in the CI pipeline, it is automatically deployed to staging or production environments. CD pipelines often include additional automated tests and checks, such as performance testing, security testing, and user acceptance testing, to ensure that the software is production-ready.
Advantages of continuous delivery
Implementing CD in your software development process has several benefits:
- Rapid releases: CD allows development teams to deploy new features and bug fixes quickly, enabling them to respond to customer needs and market changes more effectively.
- Reduced risk: By automating the deployment process, CD minimizes human error and ensures that the software is always in a production-ready state, reducing the risk of failed deployments and downtime.
- Improved feedback: CD enables teams to gather user feedback on new features and improvements more quickly, allowing them to iterate and improve their software rapidly.
CI vs CD: Similarities and Differences
Although CI and CD are typically used together, it’s essential to understand the similarities and differences between these two practices.
Similarities between CI and CD
CI and CD are similar in several aspects:
- Focus on automation: Both CI and CD rely on automating various aspects of the software development and release process, from building and testing code to deploying it in production.
- Quality assurance: CI and CD both emphasize maintaining a high-quality codebase and ensuring that the software is always in a releasable state.
- Frequent integration and deployment: CI and CD encourage frequent integration of code changes and rapid deployment of new features and bug fixes, enabling teams to stay agile and responsive.
Differences between CI and CD
Before discussing the differences, it is important to realize that an organization can have CI on its own, but CD cannot exist without CI, because it works on artifacts generated by a CI system.
Key differences between CI and CD include:
- Scope: CI focuses on automating the integration and testing of code changes, whereas CD extends this automation to the entire software release process, including deployment to production.
- Deployment: In CI, the primary goal is to ensure that the codebase is stable and integration issues are resolved. In CD, the focus shifts to automating the deployment process and ensuring that the software is always production-ready.
- Testing: While both CI and CD involve automated testing, CI usually focuses on extensive tests to verify functionality, performance, and security, while CD typically includes minimal smoke tests to make sure software is deployed and working properly in production.
Related content: Read our guide to CI/CD tools
Best Practices for Implementing CI and CD
Best Practices for Implementing Continuous Integration
Maintain a code repository
The first and most crucial practice for implementing continuous integration is to maintain a centralized code repository. This is where all the source code, configuration files, and other essential artifacts for your project should be stored. A well-maintained code repository allows developers to collaborate more efficiently, track changes in the codebase, and easily revert to previous versions when necessary.
Automate the build
Automating the build process is a critical aspect of implementing continuous integration. This means that whenever a developer pushes changes to the code repository, an automated system should compile the code, run tests, and generate relevant artifacts such as executables or documentation.
By automating the build process, you can catch integration issues early, reduce the likelihood of introducing regressions, and ensure that the code is always in a releasable state.
Make the build self-testing
Incorporating automated testing into your build process is another essential practice for continuous integration. This means that every time a build is triggered, a suite of automated tests should be run to verify that the application still functions correctly.
Automated testing helps catch issues early and reduces the time spent on manual testing. It also helps ensure that new changes do not introduce regressions into the system.
Keep the build fast
A fast build process is crucial for maintaining an efficient continuous integration pipeline. Ideally, your build should take no more than a few minutes to complete. Longer build times can slow down development and discourage developers from integrating their changes frequently.
To keep your build process fast, consider the following strategies:
- Break down your build into smaller, more targeted tasks.
- Run tests in parallel where possible.
- Use incremental builds to only compile and test changed code.
- Leverage build caching to avoid re-processing the same artifacts.
- Optimize your build scripts and tooling.
Make it easy to get the latest deliverables
One of the primary goals of continuous integration is to ensure that the code is always in a releasable state. To facilitate this, make it easy for developers, testers, and other stakeholders to access the latest build artifacts.
You can achieve this by publishing build artifacts to a centralized location, such as an artifact repository or file server, automatically notifying stakeholders when new artifacts are available, and providing clear documentation on how to access and use the artifacts.
Best Practices for Implementing Continuous Delivery
Automate the release process
Just as automating the build process is essential for continuous integration, automating the release process is crucial for continuous delivery. This means that deploying a new version of your application to production should require minimal manual intervention.
Automating the release process helps ensure consistent and reliable deployments, reduces the likelihood of human error, and allows for faster delivery of features to end-users.
Learn more in our detailed guide to software deployment
Keep everything in version control
In addition to maintaining a code repository, it is essential to keep all aspects of your application, including configuration files, environment settings, and deployment scripts, in version control. This allows you to track changes, roll back to previous versions when necessary, and ensure that all team members are working with the same baseline.
Furthermore, keeping everything in version control helps maintain consistency between different environments, such as development, staging, and production. This reduces the likelihood of issues arising due to configuration discrepancies or missing dependencies.
Build a staging environment that mirrors production
A key aspect of continuous delivery is ensuring that your application behaves consistently across different environments. To achieve this, it is crucial to have a staging environment that closely mirrors your production environment.
A staging environment allows you to test your application under realistic conditions, catch environment-specific issues before they reach production, and minimize the risk of failed deployments. Ensure that your staging environment is kept up to date with the latest production settings, and use it to validate your application before promoting it to production.
Build quality in
Continuous delivery relies on the assumption that the code is always in a releasable state. To maintain this level of quality, it is essential to prioritize quality throughout the entire development process.
Some strategies for building quality into your application include:
- Writing clean, maintainable code.
- Incorporating automated testing at all levels, from unit tests to integration tests and end-to-end tests.
- Conducting regular code reviews to catch issues early and share knowledge among team members.
- Using static analysis tools to catch potential issues before they become problems.
- Monitoring your application in production to identify and resolve issues quickly.
Done means released
Finally, to fully embrace continuous delivery, it is essential to adopt the mindset that “done” means “released.” This means that once a feature is complete and has passed all necessary tests, it should be deployed to production as soon as possible.
By releasing features quickly and frequently, you can gather feedback from end-users more rapidly, iterate on your product more effectively, and ultimately deliver more value to your customers.
Continuous Integration and Continuous Delivery with Codefresh
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