Continuous Integration vs. Continuous Delivery / Deployment: What’s the Difference?

Introduction

The modern world of software development moves fast, and such practices as Continuous Integration, or CI, Continuous Delivery, CD, and Continuous Deployment are at their height of popularity. These techniques enable the teams to get the software out of the door quickly but with fewer errors.

What do all of these words actually mean, and how might these help your project? Let's break them down in simple terms.

In other words: CI keeps your code healthy, Continuous Delivery keeps your code always ready for release and Continuous Deployment is a process where every change goes right to your users.

What is Continuous Integration (CI)?

The most general definition of CI can be that it is a way of software development methodology wherein multiple developers are able to work easily with one another. In other words, it means integrating working code into one single repository-something like a central code branch-very frequently. And every time new code is added, automated tests that check if anything is broken will run.

CI aims to catch problems early. Immediately when something breaks, the developers hear of it, and thus they can act quickly to give a fix. In this way, time will not be lost and greater problems caused by hanging are not faced.

Advantages of CI:

• Bug detection early on: Acquire the habit of solving problems when they actually appear, hence making the whole development process smooth.
• Prepare for Release Faster: As the integration is continuous, thereby making preparation for release quite easy.
• Improved Team Collaboration: Since there are fewer changes in the air, the slightest amount of error or conflict between the developers isn't likely to occur.

What You Need for CI:

• Automation tests that need to run post addition of each code.
• A constantly polling server on changes and executed by itself
• Changes ready for the developers to make, frequently enough at least once a day.

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What is Continuous Delivery (CD)?

Continuous Delivery is an extension of Continuous Integration. While Continuous Integration automatically tests for correctness of code changes, Continuous Delivery will have those changes prepared to be deployed. A more accurate meaning would be that whenever there is already a new version of your code, that version could be released, with relatively little trouble, to a testing or staging environment.

Continuous Delivery means an individual can release an update on any schedule that one wants. It could be daily, weekly, monthly, and so on. The major difference between Continuous Integration is that Continuous Delivery focuses on the automation of the whole releasing process. This is all about keeping a version of your software always ready for release to production.

Advantages of CD::

• Simplified Releases: Deployment is going to be a really simple process without much friction.
• Faster Feedback: You can put out small changes more often and get user feedback faster.
• Changes Less Likely to Be Risky: Because you release in small updates you are able to fix problems more easily.

What You Need for CD:

• A solid CI base: your tests should cover a sufficient part of your code.
• Automated deployment scripts make it a breeze to push changes live.
• Feature flags for A/B testing: Sometimes this is used to control what a user can see before a release.

What is Continuous Deployment?

Continuous Deployment: This is the latest step of improvement, in the CI/CD process. It's the same as Continuous Delivery, except for one little difference-the every change that passed automated tests goes directly to production. No need for manual approval. This means your users can get to work almost immediately.

For teams, continuous deployment is great since it allows them to move fast. It saves them from "release days." It will let you deliver new features to users faster than ever.

Advantages of Continuous Deployment::

• Instant Feedback: Very comfortable testing novel ideas-as-user sees changes right there and then.
• Smaller, Easier Fixes: As the size of the updates is smaller than in conventional desk applications, when problems arise, debugging will be easier.
• Freedom to concentrate on development: Developers can spend more productive time building new features, rather than deal with releases.

What You Need for Continuous Deployment:

• A very strong-testing culture, whereby your automated tests ought to catch most problems.
• Documentation that moves at the pace of changes.
• Feature flags: available to introduce new features gradually, if needed.

CI vs. CD vs. Continuous Deployment: Comparison Table

A rough comparison to help explain the difference might be as follows:

Practice	Focus Area	Benefits	Needs
CI (Continuous Integration)	Merge code changes more frequently by testing on a regular basis. Find bugs earlier rather than during releases.	Robust test suite, frequent merges, and automated builds	Strong foundation of CI, automated deployments, feature flags
Continuous Delivery	Software is ready for deployment at all times after testing—easier releases, faster feedback, less stress.	Strong foundation of CI, automated deployments, feature flags	Mature testing culture, reliable tests, thorough documentation of the system and process
Continuous Deployment	Automate the release of every change.	Fast feedback, no manual approvals, smaller incremental updates	Same as Continuous Delivery needs, with a focus on automating the entire release process

Getting Started with CI/CD

For a good CI/CD process,

1. Start with CI: Pay extra attention to automating your testing process. Every change should be tested before merge.
2. Extend to CD: Automate the processes for deploying staging environments. In that way, more extensive testing can be performed before a release of a new version.
3. Switch to Continuous Deployment: If you get comfortable, automate the release to production. This may save some time and make your team more prolific.

Final Thoughts

Continuous Integration, Continuous Delivery, and Continuous Deployment enable your team to rethink the way it delivers its software. They allow for finding problems a lot sooner with reduced complexity of the releases and quicker delivery. Be it a small startup or a huge enterprise, it's going to result in far better software being built much faster.