Those familiar with DevOps know that continuity lies at the heart of its life cycle, which underpins its core concepts of continuous integration, continuous deployment, and continuous delivery (CI/CD/CD), three terms that many often get confused with since they are often used interchangeably. But despite this common practice, they are not one and the same despite all being a part of the software delivery process. In fact, each has its own benefits and requirements. Since understanding their differences is key to properly implementing them, this article explores what sets them apart.
An overview of CI/CD/CD
As stated, these three approaches differ in what they mean to development teams and, most importantly, their implementation. A good way to think about CI/CD/CD is a timeline where continuous integration starts at the beginning as it serves as the foundation for the continuous deployment or delivery that follows. Hence, it is bad practice to implement continuous deployment or delivery first, ahead of continuous integration. With that in mind, let us go over what each stands for.
Continuous Integration
CI is the practice of merging the changes to the code base to the version control’s system main branch as frequently as possible once they are tested. Validating these changes involves making a build and performing automated tests against it. If these tests fail, the changes will not be merged so that dev teams avoid integration issues. The main advantage of CI is the reduction of bugs making their way to production since problems are caught early on and resolved before release.
Continuous Delivery
Continuous Delivery (CD) serves as an extension of continuous integration as it leverages automation in deploying all code changes to different environments once they are merged with the main branch. The artifact can be built as part of continuous integration or part of the CD process since your repository or the source of truth is dependable, given your CI. In other words, on top of the automated testing process, there is an automated release process that lets developer teams deploy their changes at any time or whenever CI is completed. Because of this capability, deploying changes to production regularly is recommended to simplify troubleshooting and allow customers to get their hands on the best version of the product as soon as possible.
Continuous Deployment
Continuous deployment (CD) takes continuous delivery a step further by releasing all the changes that pass the verification stages in the pipeline into production. Automation is used to manage this entire process, and pushing the changes will only be halted whenever a failure is encountered in any of the verification steps. CD benefits not only the customers who receive faster updates but also developers who receive the former’s feedback more quickly, enabling them to deploy small changes incrementally instead of big updates that put more pressure on them.
Continuous Integration vs Continuous Deployment vs Continuous Delivery
As explained, CI is simply integrating changes to the code base into the main branch or source of truth using platforms specifically designed for such purposes. In contrast, continuous delivery occurs once said changes have been integrated and bring them to the customer’s hands. Thus, continuous integration and continuous delivery are not different approaches but rather complementing ones.
On the other hand, the difference between continuous integration and continuous deployment is similar to that of the above, with the exception of continuous deployment using automation to push changes to the customers without human intervention.
Last but not least, continuous delivery is partly a manual process that requires developers or non-technical team members to release the changes, while continuous deployment automates this process.
The risks of focusing solely on Continuous Integration
Knowing the difference between these three is vital since many businesses tend to conflate continuous delivery and continuous development to the point that they only prioritize continuous integration. This confusion may also lead some to think that they are not ready for the continuous deployment and therefore neglect it altogether.
It is important to note that setting up a CI server that continuously merges and integrates code changes does not mean you are practicing continuous delivery. Properly implementing continuous delivery requires the right tools for software testing, staging, and deployment, which can handle all these processes automatically and continuously.
Conclusion
All in all, continuous integration is indispensable and must be implemented before starting with continuous delivery or deployment. That does not mean continuous delivery is less important (it is more so in truth), but rather neglecting to implement it correctly significantly reduces stability and reliability. Hopefully, by having a clearer understanding of what sets these terms apart, you now have a better idea of how to implement them properly.
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