What is continuous integration, continuous delivery, and continuous deployment?
Continuous Integration (CI) is a software development practice where developers regularly merge their code changes into a central repository, after which automated builds and tests are run. CI most often refers to the build or integration stage of the software release process and requires both an automation component (for example, a CI or build service) and a cultural component (for example, learning to integrate frequently). The critical goals of CI are to find and address bugs more quickly, improve software quality, and reduce the time it takes to validate and release new software updates.
Continuous Integration focuses on smaller commits and smaller code changes to integrate. A developer commits code at regular intervals, at minimum once a day. The developer pulls code from the repository to ensure the code on the local host is merged before pushing it to the build server. At this stage, the build server runs the various tests and accepts or rejects the code commit.
The fundamental challenges of implementing CI include more frequent commits to the shared codebase, maintaining a single source code repository, automating builds, and automating testing. Additional challenges include testing in similar environments to production, providing visibility of the process to the team, and allowing developers to obtain any version of the application quickly.
Continuous Delivery (CD) is a software development practice where code changes are automatically built, tested, and prepared for production release. It expands on continuous integration by deploying all code changes to a testing environment, a production environment, or both after the build stage has been completed. Continuous delivery can be fully automated with a workflow process or partially automated with manual steps at critical points. When continuous delivery is appropriately implemented, developers always have a deployment-ready build artifact that has passed a standardized test process.
Continuous Deployment automatically deploys revisions to a production environment without explicit approval from a developer, making the entire software release process automated. This, in turn, allows for a continuous customer feedback loop early in the product lifecycle.
Continuous Delivery is not continuous Deployment. One misconception about continuous delivery is that every change committed is applied to production immediately after passing automated tests. However, the point of continuous delivery is not to immediately apply every change to production but to ensure that every change is ready to go to production.
Before deploying a change to production, a decision process can be implemented to ensure that the production deployment is authorized and audited. This decision can be made by a person and then executed by the tooling.
Using continuous delivery, the decision to go live becomes a business decision, not a technical one. The technical validation happens on every commit.
Rolling out a change to production is not a disruptive event. Deployment doesn’t require the technical team to stop working on the next set of changes; it doesn’t need a project plan, handover documentation, or a maintenance window. Deployment becomes a repeatable process that has been carried out and proven multiple times in testing environments.
Image Credits: GitLab
Article Credits: Adit Modi
Adit is a Cloud Engineer at Digital Alpha | 9x AWS | AWS Community Builder | HashiCorp Ambassador