Runtime Adaptation for Actor Systems

Abstract

Abstract. We study the problem of extending RV techniques in the context of (asynchronous) actor systems, so as to be able to carry out a degree of system adaptation at runtime. We propose extensions to specification logics that provide handles for programming both monitor synchronisations (with individual actors), as well as the administration of the resp. adaptations once the triggering behaviour is observed. Since this added functionality allows the specifier to introduce erroneous adaptation procedures, we also develop static analysis techniques based on substructural type systems to assist the construction of correct adaptation scripts.

A Suite of Monitoring Tools for Erlang

“…Even though several monitoring tools [14,23,15,20] exists for renowned languages such as Java, the only tools developed specifically for Erlang are detectEr [4,7] and adaptEr [9,8]. In this paper we therefore give an overview of these two runtime monitor tools.…”

“…Adaptation actions are rectifying actions (such as restarting or terminating misbehaving actors) in order to mitigate the effects incurred by a detected violation. This extension led to the creation of a Runtime Adaptation tool called adaptEr [8,9]. In this property, the specifier presumes that the error (which may arise after a number of correct interactions) is caused by the interface actor i (as shown in Figure 2, where an inc request is erroneously forwarded to the decrementor actor k) -one may, for instance, have prior knowledge that actor i is a newly-installed, untested component.…”

“…In most monitoring settings [6,17,8,18] the correctness property is generally specified as a formula in a logic with precise formal semantics, from which a monitor is then automatically synthesised. This monitor is essentially the executable software which analyses the runtime execution of a program in relation to the given property.…”

“…By contrast, monitors in Runtime Adaptation (RA) [9,22,8,21] break this passivity by executing adaptation actions after analysing a particular sequence of system events. As shown in Figure 1b, rather than flagging violations, RA monitors can execute adaptation actions upon detecting an event sequence that denotes incorrect behaviour.…”

A Generic Instrumentation Tool for Erlang

“…eAOP was also embedded in a framework called AdaptEr 2 to automate runtime adaptation monitors for Erlang systems [5,6]. AdaptEr was developed as an extension to DetectEr 2.0, and can selectively apply adaptation actions to specific actors so as to either rectify the effects of a detected misbehaviour (e.g., restart a misbehaving actor) or else to improve the system based on the current state of the system (e.g., by terminating idle/redundant actor processes).…”