Continuous Deployment vs Continuous Delivery. What’s the difference?

Continuous Delivery: Shortening the time to market

This process involves the automation of steps between and starting with the build and every step that precedes the deployment process.  Approving and initiating the deployment of the build into production is done manually. This means that despite continuous delivery being automation-oriented, it includes at least one manual step (deployment).

The goal of continuous delivery is to get the new features, bug fixes, or configurations ready for deployment into a production environment in a quick and stable way. To achieve this, the build artefact has to be maintained in a deployable state at all times irrespective of the number of contributors involved in its development.

Continuous delivery allows companies to enjoy several benefits that were beyond their reach before its introduction. First, the speed of the go-to-market is increased significantly because it automates processes that used to take a significant time. Reworks are also minimized by automated testing that gives detailed information on the build’s health. Secondly, companies are able to achieve lower-risk releases by utilizing strategies such as canary release and blue-green deployments. Finally, companies get continuous feedback that plays a big role in delivering high-quality applications to the end-users.

Continuous delivery adds confidence to builds before they are delivered to a specified environment. This is because it has all the validation and testing steps required to get the build ready for deployment in a production environment.

Continuous Deployment: An end-to-end automation process

This involves the actual deployment to a production environment of changes made to the code after they have been tested for correctness and stability. Its process is completely automated and doesn’t require explicit approval from the developers involved. This is made possible by its rigorous monitoring and roll-back mechanism.

The tests conducted in continuous deployment reflect as many scenarios as possible to understand the application’s behaviour in a production environment. Some of the tests that are performed include unit tests and functional tests (both tests are also part of the continuous delivery pipeline). Frameworks that can be effectively utilized to carry out unit tests including TestNG, RSpec, and NUnit among others.

By automating the deployment process, time is freed up to focus on the actual development of the software and this increases the team’s overall productivity. Just like in continuous delivery, the continuous deployment also gives developers access to continuous customer feedback because the time to market is reduced significantly, features are tested and deployed quickly and customer-oriented tasks such as A/B tests are accessible by the business teams faster. It is important for a clear map to be defined before introducing continuous deployment because bugs missed by it will negatively impact the users’ experience.

Difference between continuous delivery vs continuous deployment

Even though continuous deployment and continuous delivery overlap, their goals are different. Below are some of the differences between the two processes.

Need for a staging area

Continuous delivery requires a staging area where new code is reviewed. The changes have to be manually accepted and this creates a time lag before the changes are made available to be released into a production environment.

On the other hand, continuous deployment does not require a staging area since the process is completely automated and requires no manual approval. This means that it offers a lag-free environment for new releases on their way to the production environment. This also means that automated testing is integrated early in the development and integration process

Scope

While continuous delivery and deployment overlap, the latter goes further into the actual deployment of the application into a selected environment. Continuous delivery ensures that builds are continually being processed to be in a deployable state but don’t perform the actual deployment. Once the artifact gets to this stage, it needs to be manually validated and approved for it to proceed.

Continuous deployment on the other hand deploys the artifact into a selected environment. This can be a production environment or a deployment slot where more tests can be undertaken without impacting the application’s users.

Testing

Continuous deployment performs tests that are aimed at evaluating how the build will perform in a production environment. Continuous delivery tests are meant to ensure that the features are working well and the application is bug-free.

To summarize

The two processes add agility and speed to the app development and deployment process. Their strength is in providing a continuous flow of updates, feedback, fixes, and testing with the goal of making high-quality applications available to the end-users. Even though there is an overlap between the two their goals are different. Continuous delivery aims to always have the builds in a deployable stage and continuous deployment aims to continually deploy updated applications.

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