The continuous delivery approach involves fast software development iterations and frequent, safe updates to the deployed application. It is all about reducing risk and delivering value faster by producing reliable software in short iterations. Because Docker encapsulates both the application and the application's environment or infrastructure configuration, it provides a key building block for two essential aspects of a continuous delivery pipeline. Docker makes it easy to test exactly what you are going to deploy. The possibility of making serious errors during the handoff or bringing in any undesirable changes is less likely in this case. Docker containers encourage a central tenet of continuous delivery: they reuse the same binaries at each step of the pipeline to ensure no errors are introduced in the build process itself.

As indicated earlier, Docker containers provide the basis for immutable infrastructures. Applications can be added, removed, cloned, and/or their constituencies can change without leaving any residues behind. IT infrastructures can be changed without affecting the applications that run on them. The Docker tool ecosystem is the growth trajectory and hence a lot of delivery-related works get simply automated and accelerated to add business value. As Martin Fowler says, you actually do continuous delivery in the following situations:

• If your software is deployable throughout its life cycle
• If your team prioritizes keeping the software deployable over working on new features
• If anybody can get fast, automated feedback on the production readiness of their systems anytime somebody makes a change to them
• If you can perform push-button deployments of any version of the software to any environment on demand

Docker also easily integrates with CI and continuous delivery platforms enabling development and testing to deliver seamless updates to production. In the case of any kind of failure, it is possible to roll back to the previous working version.