Scoped Synchronization Constraints for Large Scale Actor Systems

Abstract

Very large scale systems of autonomous concurrent objects (Actors) require coordination models to meet two competing goals. On the one hand, the coordination models must allow Actors to dynamically modify protocols in order to adapt to requirement changes over the, likely extensive, lifetime of the system. On the other hand, the coordination models must enforce protocols on potentially uncooperative Actors, while preventing deadlocks caused by malicious or faulty Actors. To meet these competing requirements, we introduce a novel, scoped semantics for Synchronizers [7,6]-a coordination model based on declarative synchronization constraints. The mechanism used to limit the scope of the synchronization constraints is based on capabilities and works without central authority. We show that the mechanism closes an attack vector in the original Synchronizer approach which allowed malicious Actors to intentionally deadlock other Actors.

Why Do Scala Developers Mix the Actor Model with other Concurrency Models?

“…More advanced coordination mechanisms for actor systems have also been proposed [4,31,9,27]. However,to the best of our knowledge, none has been integrated with a widely used actor library.…”

Specifying Languages and Verifying Programs with K

“…K's ability to express truly concurrent computations has been used in researching safe models for concurrency [20], synchronization of agent systems [21], models for P-Systems [22], [23], and for the x86-TSO relaxed memory model [24]. K has been used for designing type checkers/inferencers [25], for model checking executions with predicate abstraction [26], [27] and heap awareness [28], for symbolic execution [29]- [31], computing worst case execution times [32], [33], studying program equivalence [34], and runtime verification [24], [35].…”

Optimized distributed implementation of multiparty interactions with Restriction

“…In [23,21], Synchronizers are used to filter incoming messages for a set of actors. A message is delivered only if it matches an enabled pattern.…”

“…Such patterns include atomic synchronization of a set of messages, that requires all involved messages to be pending before granting their transmission. According to [21], synchronizers are implemented through dispatchers located on the target actors, that is the actors for which incoming messages are filtered. Upon reception of an incoming message, the dispatcher is responsible for checking whether the message is allowed for transmission according to the synchronizers.…”