What's the difference between continuous integration, delivery and deployment

If you are working in the information technology industry or are interested in that, you have heard the question “What is a CI/CD pipeline?”. CI/CD or the process of continuous integration and continuous delivery can be called the heart of the modern software engineering industry. Through this article, we are going to get to know what is CI and CD, why it is that important, the difference between CI and CD, and how CI and CD relate to each other in the software development process.

What is CI and CD?

“What is a CI/CD pipeline?” This is a common question when it comes to software development. Continuous Integration or CI is a software development practice that should be followed by everyone involved in the software development process. There they frequently integrate their code changes into a shared repository which includes all the code changes of the team members. 

The main goal of CI is to automate the code integration process and detect integration issues at the earliest in the development cycle. In CI, after the developers are done with their respective code changes, they submit them to a version control system such as Git, trigger an automated build process, and test.

Continuous Delivery or CD mainly focuses on automating the entire process of software release. Through CD every change is automatically built then goes through the testing phase and is finally released to production. While CI ensures that code changes are integrated and tested regularly, CD automates the delivery of those changes to the required testing environments and other higher environments such as staging and production. 

In a CD pipeline, the code changes that have already passed the automated tests during CI are automatically deployed to the stage/QA environments and it allows the team members to conduct additional testing tasks before deploying that code to the production environment.

Why are they important?

CI and CD play a major role in modern software development. Let’s get to know some of their key benefits which help to improve the software development life cycle.

• Reduce bugs 

Since developers integrate their code changes into a shared repository while using continuous integration, it is easier for them to detect integration issues earlier if there are any. CD extends this practice to the test environments and it allows further testing before deploying the code to the production. This ultimately leads to a more stable codebase with less count of bugs.

• Save time

Since CI automates the build and test process and CD speeds up the deployment process, the whole development cycle gets accelerated along with the enhancements and respective bug fixes. With CI/CD, there is no need to do repetitive tasks manually in the development process since the automated tasks are just one click away. On the other hand, automated testing in CI/CD helps the developers and testers detect and fix issues at the earliest.

• Save cost

While CI automates repetitive tasks such as build and testing, CD decreases human involvement in the deployment process. These increase the efficiency and the quality of the process ultimately saving a lot of costs that can be wasted with manual processes.

• Increase consistency and reliability

CI is a consistent and repeatable process when it comes to code building and testing. CD spreads this consistency to the deployment process. All in all, they improve the reliability of software releases while increasing the overall quality.

How do they relate to each other

Continuous integration and continuous delivery are closely related to each other and they work together to sharpen both the development and software release processes. We know that CI is the base of CD since CI ensures that the code changes are continuously integrated and tested before CD takes those pre-tested changes and automates the deployment process to higher environments. 

Even though CI makes sure that the code is integrated with no issues, CD has to set the stage for automated deployments and it completes the development cycle by going through the deployment process again to add the developed and tested code to the production environments. However, we should know that even though CI/CD are related to each other, there is a major difference between CI and CD.

Continuous integration explained

Continuous Integration is a very important practice in the development process. It focuses on automating the integrated code changes from multiple contributors into a shared repository frequently. Once the code changes are submitted, an automated build process is triggered to compile the code and it creates a build artifact. This system then runs a set of tests to ensure the new code works well with the existing code. As a special benefit, the developers quickly get feedback on whether their code passed these tests or not.

Continuous delivery explained

The code changes can be moved to continuous delivery when those are gone through the CI pipeline. The main objective of CD is to ensure that the code in the repository is always in a deployable state, and can be deployed to production at any time. 

The CD sends the code changes to testing environments such as staging environments or QA environments. This is also done as an automated process. After the code is deployed to the test environments, the testers can perform testing as they want. If those code changes need to go to the production environment, developers might need to do additional reviews and get approval from the QA team before deploying the changes to production.

Continuous Delivery includes automated testing, configuration management, and deployment automation. Once code undergoes the CI phase, it goes through further automated testing and is prepared for release. However, the actual deployment to production is taken as a manual decision.

Continuous deployment explained

Continuous Deployment can be considered an extended version of continuous delivery. This involves automating the whole release process so that all the successful code changes are automatically deployed to production without manual involvement. This means that it helps to deploy code changes to the production environment using an automated way. After the testing is done in the testing environment, developers release the code changes to the production environments which have already passed the previous stages.

Similar to Continuous Delivery, but the difference is that, in Continuous Deployment, the deployment to production is fully automated. Once the code passes all testing phases, it is automatically released to production without human approval.

Typically, the QA team decides whether to promote or reject a build based on the test results obtained in the stage/QA environments. If the QA team approves the build with a +1, the DevOps team/SRE team proceeds to deploy the build to production. On the other hand, if the QA team rejects the build due to any L1/blockers, it is sent back to the development environment for addressing the identified L1 issues.

Conclusion

CI/CD practices play an important role in software development. Continuous Integration automates the integration of new code with the legacy code and its associated testing tasks. Continuous Delivery takes care of automating the release of these code changes to testing environments. 

CI/CD practices catch and fix errors early, keep everything consistent, and save both time and money. CI is the foundation and it ensures that code changes are integrated and tested correctly. CD automates how these changes get to testing and live environments. Together, CI/CD practices make software development and release faster and more reliable. At the end of the day, it leads to a costless and high-quality software product.

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