Extraction of Microservices from Monolithic Software Architectures

Driven by developments such as mobile computing, cloud computing infrastructure, DevOps and elastic computing, the microservice architectural style has emerged as a new alternative to the monolithic style for designing large software systems. Monolithic legacy applications in industry undergo a migration to microservice-oriented architectures. A key challenge in this context is the extraction of microservices from existing monolithic code bases. While informal migration patterns and techniques exist, there is a lack of formal models and automated support tools in that area. This paper tackles that challenge by presenting a formal microservice extraction model to allow algorithmic recommendation of microservice candidates in a refactoring and migration scenario. The formal model is implemented in a web-based prototype. A performance evaluation demonstrates that the presented approach provides adequate performance. The recommendation quality is evaluated quantitatively by custom microservice-specific metrics. The results show that the produced microservice candidates lower the average development team size down to half of the original size or lower. Furthermore, the size of recommended microservice conforms with microservice sizing reported by empirical surveys and the domain-specific redundancy among different microservices is kept at a low rate.