Continuous Delivery (CD) and Continuous Deployment (CI/CD) are two practices in software development and release management that are closely related but have distinct differences:
Continuous Delivery (CD):
Continuous Delivery is a software development practice where code changes are automatically built, tested, and prepared for release to a staging or pre-production environment. However, the actual deployment to the production environment is a manual decision made by a human.
Key characteristics of Continuous Delivery include:
- Automated testing: Code changes go through automated testing, including unit tests, integration tests, and acceptance tests.
- Staging environment: Code changes are deployed to a staging or pre-production environment that closely resembles the production environment.
- Manual approval: Before code is deployed to the production environment, it requires manual approval by a person or a team, often a product owner or a release manager.
- Reduced risk: CD aims to reduce the risk of deploying untested or unstable code to the production environment.
In Continuous Delivery, the deployment to production is a controlled and deliberate process. This allows teams to thoroughly test changes in a staging environment and ensure that only stable and approved code is promoted to production.
Continuous Deployment (CI/CD):
Continuous Deployment is an extension of Continuous Delivery, where code changes that pass automated tests are automatically and immediately deployed to the production environment without manual intervention. This means that every successful code change is automatically released to production, assuming it passes all tests.
Key characteristics of Continuous Deployment include:
- Fully automated: The deployment process is entirely automated, from code integration, testing, to production deployment.
- Immediate release: Successful code changes are immediately deployed to the production environment, often multiple times a day.
- High level of confidence: Teams practicing Continuous Deployment typically have a high level of confidence in their automated testing and monitoring systems.
Continuous Deployment is often associated with fast-paced development environments, such as those in startups or web-based applications, where the ability to quickly release new features and bug fixes is a competitive advantage.
In summary, the main difference between Continuous Delivery and Continuous Deployment is the level of automation and the final step of deployment to production. Continuous Delivery stops at the staging environment and requires manual approval for production deployment, while Continuous Deployment automates the entire process, deploying code changes to production automatically once they pass automated tests. The choice between these practices depends on the specific needs, risk tolerance, and development culture of an organization.