Continuous Delivery is a software development practice where software is always in a releasable state. Teams produce software in short cycles, ensuring that the software can be reliably released at any time. By relying on automated testing and deployment, as well as ensuring collaboration and communication between development and operational teams (DevOps), the goal of building, testing, and releasing software faster and more frequently can be achieved. This approach can help to reduce the cost, time and risk of delivering changes by allowing for more incremental updates to applications and configuration items (CIs) into production.
A straightforward and repeatable deployment process is important for continuous delivery and will be critical for operational processes such as Change Management and Release and Deployment Management to be agile and robust in the DevOps environments where continuous delivery will be part of best practices.
Continuous Delivery is sometimes confused with Continuous Deployment. Continuous Deployment means that every change is automatically deployed to production. Continuous Delivery means that the team ensures every change can be deployed to production but may choose not to do so, usually due to business reasons. In order to do Continuous Deployment one must be doing Continuous Delivery. (1)
Continuous delivery is enabled through the deployment pipeline. The purpose of the deployment pipeline has three components: Visibility, Feedback and Continually Deploy. (2)
· Visibility – All aspects of the delivery system including building, deploying, testing and releasing are visible to every member of the team to promote collaboration.
· Feedback – Team members learn of problems ASAP when they occur so that they are able to fix them as quickly as possible.
· Continually Deploy – Through a fully automated process you can deploy and release any version of the software to any environment.
Continuous Delivery also requires that whenever anyone makes a change that causes an automated test to fail, breaking the deployment pipeline, the pipeline and all associated systems must be brought back into a deployable state. In some cases, the Standard Operating Procedure (SOP) may be to have continuous integration and deployment reject any changes that take the code or configuration out of a deployable state.
Remember it is all about “Flow” in which continuous delivery is just one of many practices utilized in the “First Way”.
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2. Duvall Paul /Continuous Delivery: Patterns and Anti-Patterns in Software Lifecycle"