Experience Report: An Empirical Study of API Failures in OpenStack Cloud Environments
Pooya Musavi, Bram Adams, Foutse Khomh · 2016
Stories about service outages in cloud environments have been making the headlines recently. In many cases, the reliability of cloud infrastructure Application Programming Interfaces (APIs) were at fault. Hence, understanding the factors affecting the reliability of these APIs is important to improve the availability of cloud services. In this study, we mined bugs of 25 modules within the 5 most important OpenStack APIs to understand API failures and characteristics. Our results show that in OpenStack, only one third of all API-related changes are due to fixing failures, with 7% of all fixes even changing the API interface, potentially breaking clients. Through qualitative analysis of 230 sampled API failures we observed that the majority of API related failures are due to small programming faults. Fortunately, the subject, message and stack trace as well as reply lag between comments included in these failures' bug reports provide a good indication of the cause of the failure.