An Approach to Recommendation of Verbosity Log Levels Based on Logging Intention

Verbosity levels of logs are designed to discriminate highly diverse runtime events, which facilitates system failure identification through simple keyword search (e.g., fatal, error). Verbosity levels should be properly assigned to logging statements, as inappropriate verbosity levels would confuse users and cause a lot of redundant maintenance effort. However, to achieve such a goal is not an easy task due to the lack of practical specifications and guidelines towards verbosity log level usages. The existing research has built a classification model on log related quantitative metrics such as log density to improve logging level practice. Though such quantitative metrics can reveal logging characteristics, their contributions on logging level decision are limited, since valuable logging intention information buried in logging code context can not be captured. In this paper, we propose an automatic approach to help developers determine the appropriate verbosity log levels. More specially, our approach discriminates different verbosity log level usages based on code context features that contain underlying logging intention. To validate our approach, we implement a prototype tool, VerbosityLevelDirector, and perform a case study to measure its effectiveness on four well-known open source software projects. Evaluation results show that VerbosityLevelDirector achieves high performance on verbosity level discrimination and outperforms the baseline approaches on all those projects. Furthermore, through applying noise handling technique, our approach can detect previously unknown inappropriate verbosity level configurations in the code repository. We have reported 21 representative logging level errors with modification advice to issue tracking platforms of the examined software projects and received positive feedback from their developers. The above results confirm that our work can help developers make a better logging level decision in real-world engineering.