Studying the use of Java logging utilities in the wild

Software logging is widely used in practice. Logs have been used for a variety of purposes like debugging, monitoring, security compliance, and business analytics. Instead of directly invoking the standard output functions, developers usually prefer to use logging utilities (LUs) (e.g., SLF4J), which provide additional functionalities like thread-safety and verbosity level support, to instrument their source code. Many of the previous research works on software logging are focused on the log printing code. There are very few works studying the use of LUs, although new LUs are constantly being introduced by companies and researchers. In this paper, we conducted a large-scale empirical study on the use of Java LUs in the wild. We analyzed the use of 3, 856 LUs from 11,194 projects in GitHub and found that many projects have complex usage patterns for LUs. For example, 75.8% of the large-sized projects have implemented their own LUs in their projects. More than 50% of these projects use at least three LUs. We conducted further qualitative studies to better understand and characterize the complex use of LUs. Our findings show that different LUs are used for a variety of reasons (e.g., internationalization of the log messages). Some projects develop their own LUs to satisfy project-specific logging needs (e.g., defining the logging format). Multiple uses of LUs in one project are pretty common for large and very largesized projects mainly for context like enabling and configuring the logging behavior for the imported packages. Interviewing with 13 industrial developers showed that our findings are also generally true for industrial projects and are considered as very helpful for them to better configure and manage the logging behavior for their projects. The findings and the implications presented in this paper will be useful for developers and researchers who are interested in developing and maintaining LUs.