The Existence and Co-Modifications of Code Clones within or across Microservices

In recent years, microservice architecture has been widely applied in software design. In addition, more and more monolithic software systems have been migrated into a microservice architecture. The core idea is to decompose the concerns of software projects into small and loosely-coupled services. Each service is supposed to be developed and even managed independently, which in turn improving the efficiency of development and maintenance. Code clone is common during software implementations, and many prior studies have revealed that code clones could cause maintenance difficulties. However, there is little work exploring the impacts of code clones on microservice projects. To bridge this gap, we focus on exploring the existence and co-modifications of within-service and cross-service code clones. With our evaluation of eight microservice projects, we have presented that there still exist code clones within services or across services. In addition, both within-service and cross-service code clones have been involved in co-modifications, meaning that these clones have caused maintenance difficulties. Finally, we have explored the characteristics of co-modifications in terms of changed LOC for both within-service and cross-service code clones.