Containerizing Continuous Delivery in Java

Chapter 3. The Impact of Docker on Java Application Architecture

“If you can’t build a [well-structured] monolith, what makes you think microservices are the answer?”

Simon Brown, Coding the Architecture

Continuously delivering Java applications within containers require several long-standing architectural patterns and paradigms be challenged. The potential for automation and immutability that containers provide (along with new properties imposed like resource-restriction and transience) means that new architecture and configuration approaches are required. This chapter looks at examples of these changes, such as the Twelve-Factor Application, the decomposition of monolithic applications into smaller API-driven composable components (microservices), and the need to develop mechanical sympathy—an appreciation and respect for the underlying deployment fabric.

Cloud-Native Twelve-Factor Applications

In early 2012, Platform-as-a-Service (PaaS) pioneer Heroku developed the Twelve-Factor App, a series of rules and guidance for helping developers build cloud-ready PaaS applications that:

• Use declarative formats for setup automation, to minimize time and cost for new developers joining the project
• Have a clean contract with the underlying operating system, offering maximum portability between execution environments
• Are suitable for deployment on modern cloud platforms, minimizing the need for servers and systems administration
• Minimize divergence between development and production, ...