Public PhD Thesis Defense of Carmine Vassallo
Advisor: Prof. Dr. Harald C. Gall
2nd Advisor: Prof. Dr. Laurie Williams
3rd Advisor: Prof. Dr. Sebastian Proksch
Chair: Prof. Dr. Davide Scaramuzza
Date and time: Friday, September 18, 2020, 16:00 h
Location: remotely via “Zoom” (here)
Extended Abstract: Continuous Integration (CI) is a software development practice that enables developers to build reliable software faster. Given its proven benefits, such as increased developer productivity and higher release frequency, most organizations have started adopting CI. This practice advocates full automation of all build steps (i.e., compilation, testing, and code quality assessment) to create a new version of the software. However, the mere introduction of an automated build infrastructure is not sufficient to practice CI well and to achieve its goals. Organizations have also to foster the application of several principles, such as commit often, that reduce conflicts in the team and ensure that the build is continuously executable. Living up to these principles is not easy especially when developers face tough deadlines. As a consequence, developers tend to deviate from principles generating anti-patterns, which are ineffective solutions to recurrent problems. Anti-patterns appear to be beneficial, but, in the end, they let CI decay and lower its effectiveness. In this dissertation, we characterize the problem of anti-patterns to implement solutions that help developers remove the root causes of anti-patterns and, therefore, follow principles. Based on the results of a preliminary study performed on opensource projects revealing the existence of deviations from core principles, we empirically derive a catalog of 79 anti-patterns encountered by developers in practice conducting semi-structured interviews with 13 practitioners and manually analyzing 2,300 posts from a well-know forum (i.e., StackOverflow) where users discuss issues related to the adoption of CI. By interpreting the resulting catalog of anti-patterns, we identify four main causes for their presence, which are (i) the poor knowledge of prerequisites for adopting CI, (ii) the difficulty of inspecting build failure logs, (iii) the presence of bad configurations, and (iv) the wrong usage of a CI process. While only better coaching in CI can efficiently remove the former, we implement several approaches to address the other causes. To improve the understandability of build failure logs, we first build a taxonomy of build failures through the manual analysis of errors contained in 34,182 build logs from open-source and closed-source projects, and then we develop a tool called BART that produces summaries for the most common build failure types. We evaluate the performance of our tool in a controlled experiment with 17 developers. To identify violations of CI principles in the form of configuration smells that developer should remove, we propose CDLinter, a semantic linter for CI/CD configuration files that is evaluated opening 145 issues in open-source projects and monitoring the acceptance of our bug reports and the removal of reported smells over a period of six months. Finally, we implement CI-Odor, an automated reporting tool that leverages information from repository and build history to monitor the presence of bad practices that slowly creep into a project over time. We evaluate its usefulness sending developers reports produced for 36 open-source projects. The results of our evaluations show that the proposed approaches are effective at removing and identifying the aforementioned causes of anti-patterns and, consequently, enforcing a principle-driven continuous integration. BART improves the understandability of the most common build failure types and developers are faster in solving build failures. In presence of build summaries, the resolution time is reduced by 23% when solving testing failures, 20% when repairing compilation errors, 43% when fixing missing dependencies, and 62% when dealing with code analysis failures. CD-Linter identifies smells that are relevant for developers. During the 6-month observation period, 53% of the project maintainers react positively to the issues detected by CD-Linter, with 9% that confirm the validity of the reported problem and 44% that fix it. Finally, the reports generated by CI-Odor are useful for monitoring anti-patterns. Many developers (67%) expect a positive effect of using our generated reports on their CI discipline and the majority (55%) is already willing to integrate CI-Odor in their CI processes.