From monolithic to microservice architecture: an automated approach based on graph clustering and combinatorial optimization

Migrating from a legacy monolithic system to a microservice architecture is a complex and time-consuming process. Software engineers may strongly benefit from automated support to identify a high-cohesive and loose-coupled set of microservices with proper granularity. The automated approach proposed in this paper extracts microservices by using graph clustering and combinatorial optimization to maximize cohesion and minimize coupling. The approach performs static analysis of the code to obtain a graph representation of the monolithic system. Then, it uses graph clustering to detect high-cohesive communities of nodes using the Louvain community algorithm. In parallel, the tool clusters the domain entities (i.e., classes representing uniquely identifiable concepts in a system domain) within bounded contexts to identify the required service granularity. Finally, it uses combinatorial optimization to minimize the coupling, hence deriving the microservice architecture. The approach is fully implemented. We applied it over four different monolithic systems and found valuable results. We evaluated the identified architectures through cohesion and coupling metrics, along with a comparison with other state-of-the-art approaches based on features such as granularity level, number of produced services, and methods applied. The approach implementation and the experimental results are publicly available.