Thespis: Causally-consistent OLTP.

Data Consistency defines the validity of a data set according to some set of rules, and different levels of data consistency have been proposed. Causal consistency is the strongest type of consistency possible when data is stored in multiple locations, and fault tolerance is desired. Thespis is a middleware that leverages the Actor model to implement causal consistency over a DBMS, whilst abstracting complexities for application developers behind a REST interface. ThespisTRX is an extension that provides read-only transaction capabilities, whilst ThespisDIIP is another extension that handles distributed integrity invariant preservation. Here, we analyse standard transactional workloads on the relational data model, which is richer than the key-value data model supported by the Thespis interface. We show the applicability of the Thespis approach for this data model by designing new operations for the Thespis interface, which ensure correct execution of such workloads in a convergent, causally-consistent distributed environment.