Efficient upgrading in a purely functional component deployment model

Abstract

Safe and efficient deployment of software components is an important aspect of CBSE. The Nix deployment system enables side-by-side deployment of different versions and variants of components, complete installation, safe upgrades, and safe uninstalls through garbage collection. It accomplishes this through a purely functional deployment model, meaning that the file system content of a component only depends on the inputs used to build it, and never changes afterwards. An apparent downside to this model is that upgrading "fundamental" components used as build inputs by many other components becomes expensive, since all of these must be rebuilt and redeployed. In this paper we show that binary patching between sets of components enables efficient deployment of upgrades in the purely functional model, transparently to users. Sequences of patches can be combined automatically to enable upgrading between arbitrary versions. The approach was empirically validated. © Springer-Verlag Berlin Heidelberg 2005.