Stateful distributed interposition

Interposition-based system enhancements for multitiered servers are difficult to build because important system context is typically lost at application and machine boundaries. For example, resource quotas and user identities do not propagate easily between cooperating services that execute on different hosts or that communicate with each other via intermediary services. Application-transparent system enhancement is difficult to achieve when such context information is obscured by complex service interaction patterns. We propose a basic mechanism for sharing contextual information across the tiers of multitier computations to support system enhancement for multitier servers and applications. This article introduces generic, cluster-wide context as a new, configurable abstraction for the OS. System administrator- or application-specified context tracking rules determine how context is associated with system processes, sockets, messages, how it is relayed along the interapplication communication channels, and how it is to be interpreted by system interpositions, thus realizing Stateful Distributed Interposition.