On the Usefulness of Automatically Generated Microservice Architectures

The modernization of monolithic legacy systems with microservices has been a trend in recent years. As part of this modernization, identifying microservice candidates starting from legacy code is challenging, as maintainers may consider many criteria simultaneously. Multi-objective search-based approaches represent a promising state-of-the-art solution to support this decision-making process. However, the rationale to adopt each microservice candidate automatically identified by these approaches is poorly investigated in industrial cases. Furthermore, studies with these approaches have not carefully investigated how maintainers reason and make decisions when designing microservice architectures from legacy systems. To address this gap, we conducted an on-site case study with maintainers of an industrial legacy system to investigate the usefulness of automatically generated microservice architectures. We analyze design decisions pointed out by the maintainers when reasoning about microservice candidates using several criteria at the same time. Our study is the first to assess a search-based approach involving actual maintainers conceiving microservice architectures in an industrial setting. Therefore, firstly, we considered individual evaluation of microservice candidates to understand the rationale for identifying a service. Secondly, we conducted a focus group study with maintainers with the goal of investigating design decisions at an architectural level. The results show that: <italic>(i)</italic> the automated approach is able to identify useful microservices; <italic>(ii)</italic> the criteria observed by previous studies are, in fact, considered by maintainers; and <italic>(iii)</italic> the maintainer profiles, i.e., the preferred granularity for microservice, highly affect design decisions. Finally, we observed the maintainers needed little effort in adjusting the automatically identified microservices to make them adoptable. In addition to indicating a promising potential of search-based approaches to generate microservice architectures, our findings highlight the need for: <italic>(i)</italic> interactive and/or customizable approaches that enable maintainers to include their preferences during the search process, and <italic>(ii)</italic> flexible or automated selection of criteria that fits the scenario in which the modernization is taking place.