What Constitutes the Deployment and Run-time Configuration System? An Empirical Study on OpenStack Projects

Modern software systems are designed to be deployed in different configured environments (e.g., permissions, virtual resources, network connections), and adapted at run-time to different situations (e.g., memory limits, enabling/disabling features, database credentials). Such a configuration during the deployment and run-time of a software system is implemented via a set of configuration files, which together constitute what we refer to as a “configuration system”. Recent research efforts investigated the evolution and maintenance of configuration files. However, they merely focused on a limited part of the configuration system (e.g., specific infrastructure configuration files or Dockerfiles), and their results do not generalize to the whole configuration system. To cope with such a limitation, we aim by this paper to better capture and understand what files constitute a configuration system. To do so, we leverage an open Card Sort technique to qualitatively study 1,756 configuration files from OpenStack, a large and widely studied open-source software ecosystem. Our investigation reveals the existence of nine types of configuration files, which cover the creation of the infrastructure on top of which OpenStack will be deployed, along with other types of configuration files used to customize OpenStack after its deployment. These configuration files are interconnected while being used at different deployment stages….