Application Frameworks

Shared libraries encourage code reuse, promote consistency across teams, and ultimately improve product velocity and quality. But application developers are still left to choose the right libraries, figure out how to correctly configure them, and wire everything together. By preinstalling and preconfiguring libraries, application frameworks provide a simplified developer experience and even greater consistency, albeit at the cost of some flexibility. By owning the entire application life cycle, frameworks go beyond a mere collection of libraries. Guaranteed framework behavior can scale development--for example, by avoiding the need for in-depth security or privacy code reviews of every application. The cross-team and cross-language consistency provided by frameworks is also a necessary foundation for higher-level automation and smart systems. This article offers an overview of the central aspects of frameworks, then dives deeper into their benefits, the trade-offs they entail, and the most important features we recommend implementing. Finally, we present a practical application of frameworks at Google: how developing a microservices platform allowed Google to break up its monolithic code base, and how frameworks enabled that change. A framework is, in many ways, similar to a shared library and has similar benefits. For Google, two technical principles help to distinguish a framework from a library: inversion of control and extensibility.