Combining stochastic process algebras and queueing networks for software architecture analysis

Abstract

We propose an integrated approach to the functional and performance analysis of Software Architectures (SAs) based on Stochastic Process Algebras (SPAs) and Queueing Networks (QNs), in order to combine their main advantages: formal techniques for the verification of functional properties of systems for SPAs, and efficient performance analysis for QNs. We first introduce AEmilia, a SPA based architectural description language for the compositional, graphical and hierarchical modeling of SAs, which is equipped with suitable checks for the detection of architectural mismatches. Then we present a systematic approach to derive QN models from AEmilia specifications. This is based on the identification of three different classes of QN basic elements -arrival processes, buffers, and service processes -and on syntactic restrictions to be imposed to AEmilia specifications, so that each architectural component directly falls into one of the three classes. Although performance analysis could be carried out directly on the Markov chain (MC) underlying an AEmilia specification, having a QN model allows performance indices to be evaluated possibly by exact product form solutions or by well known approximate methods. Furthermore, unlike the underlying MC, the high level of abstraction of the QN model should ease the interpretation of the performance results at the architectural description level.

SoftArch/MTE: Generating Distributed System Test-Beds from High-Level Software Architecture Descriptions

“…In order to avoid having to build continuously evolving performance test bed prototypes a number of architecture and middleware performance simulation and modelling methods and tools have been developed [1,9,7,18,27,24,29,36]. These make it easier for architects to express and explore likely architecture performance by providing higher-level models of architectures and using these to produce simulated or computed performance estimates for the models.…”

“…Figure 3 shows SoftArch being used to model a candidate architecture design for the video system in Figure 1 [12]. SoftArch provides a variety of predominantly graphical architecture modelling tools (1) and an extensible meta-model of available architecture elements, connectors and properties. It also provides a set of "design critics" (2) that monitor software architecture model changes and give unobtrusive user feedback.…”

“…In addition, different clients, client requests and server services may suit a different architectural arrangement. For example, simple high-volume read requests may be cached or split across multiple machines with mirrored databases, whereas different kinds of transaction processing updates are centralised on one or more machines according to their data access or remote object service access patterns [1,10,35]. Architects may want to use a different set of architectural design choices and compare their estimated performance metrics.…”

“…Most system development now requires the use of complex distributed system architectures and middleware [1,35]. Architectures are quite varied and systems may use simple 2-tier clients with a centralised database; 3-tier client, application server and database divisions of responsibility; multi-tier, decentralised web, application and database server layers; and peer-to-peer communications [1,33,35].…”

“…Architectures are quite varied and systems may use simple 2-tier clients with a centralised database; 3-tier client, application server and database divisions of responsibility; multi-tier, decentralised web, application and database server layers; and peer-to-peer communications [1,33,35]. Using each of these approaches an architect has a wide range of choice as to where to locate data processing (e.g.…”