Logging Library Migrations: A Case Study for the Apache Software Foundation Projects

Developers leverage logs for debugging, performance monitoring and load testing. The increased dependence on logs has lead to the development of numerous logging libraries which help developers in logging their code. As new libraries emerge and current ones evolve, projects often migrate from an older library to another one. In this paper we study logging library migrations within Apache Software Foundation (ASF) projects. From our manual analysis of JIRA issues, we find that 33 out of 223 (i.e., 14%) ASF projects have undergone at least one logging library migration. We find that the five main drivers for logging library migration are: 1) to increase flexibility (i.e., the ability to use different logging libraries within a project) 2) to improve performance, 3) to reduce effort spent on code maintenance, 4) to reduce dependence on other libraries and 5) to obtain specific features from the new logging library. We find that over 70% of the migrated projects encounter on average two post-migration bugs due to the new logging library. Furthermore, our findings suggest that performance (traditionally one of the primary drivers for migrations) is rarely improved after a migration.