On the rise and fall of CI services in GitHub

Continuous integration (CI) services are used in collaborative open source projects to automate parts of the development workflow. Such services have been in widespread use for over a decade, with new CIs being introduced over the years, sometimes overtaking other CIs in popularity. We conducted a longitudinal empirical study over a period of nine years, aiming to better understand this rapidly evolving CI landscape. By analysing the development history of 91,810 GitHub repositories of active npm packages having used at least one CI service, we quantitatively studied the evolution of seven popular CIs, specifically focusing on their co-usage and migration in the considered repositories. We provide statistical evidence of the rise of GitHub Actions, that has become the dominant CI service in less than 18 months time. This coincides with the fall of Travis that has seen an important decrease in usage, likely due to a combination of policy changes and migrations to GitHub Actions.