Reversibility in session-based concurrency: A fresh look

Abstract

Much research has studied foundations for correct and reliable communication-centric software systems. A salient approach to correctness uses verification based on session types to enforce structured communications; a recent approach to reliability uses reversible actions as a way of reacting to unanticipated events or failures. In this paper, we develop a simple observation: the semantic machinery required to define asynchronous (queue-based), monitored communications can also support reversible protocols. We propose a framework of session communication in which monitors support reversibility of (untyped) processes. Main novelty in our approach are session types with present and past, which allow us to streamline the semantics of reversible actions. We prove that reversibility in our framework is causally consistent, and define ways of using monitors to control reversible actions.

Runtime Verification for Decentralised and Distributed Systems

“…In a similar line, the monitors defined by Castellani et al [26,27] play a dual role: they enforce run-time adaptation policies, and ensure secure information flow in multiparty exchanges. Recent work by Mezzina and Pérez [75,76] uses monitors as the memories required to support models of concurrency in which actions are reversible and causally consistent.…”

A theory of retractable and speculative contracts

“…Reversibility, generalizing backtracking by allowing one to go back to any past state, has also been studied in the setting of binary session types [35,36,37]. There however the emphasis is on defining the reversible engine, based on causalconsistent reversibility [25], and not on studying compliance or subtyping (which would correspond to our subcontract relation).…”

Causally consistent reversible choreographies

“…e selection u ⊳ {l i .P i } i∈I is actually u, w ::= n | x, y, z n, m : a non-deterministic choice over I. In an improvement with respect to [17,18], here we consider parallel composition of processes P | Q and recursion µX.P (which binds the recursive variable X in process P ). Process V u is the application which substitutes name u on the abstraction V .…”

“…Focusing on session types [10,11] (a well established class of behavioral types), Tiezzi and Yoshida [22] were the first to integrate reversibility into a session π-calculus, following the seminal approach of Danos and Krivine [6]; in [22], however, session types are not used in the definition of reversible communicating systems, nor play a role in establishing their properties. Triggered by this observation, our prior work [17,18] develops a monitors-as-memories approach. e idea is to use monitors (run-time entities that enact protocol actions) as the memories needed to record and undo communication steps.…”

“…at is, causally consistent reversibility does not lead to extraneous states, not reachable through ordinary computations. e framework in [17,18], however, accounts only for reversible π-calculus processes implementing binary sessions, i.e., protocols between exactly two partners. Also, it considers synchronous communication instead of the more general (and practical) asynchronous (queue-based) communication.…”