Reactive Control Techniques for Autonomic Management Systems
Autonomic management systems usually involve several pieces of software designed independently from each other. As a consequence, they may take inconsistent decisions when executed in a non-coordinated manner. Using reactive control techniques, and especially synchronous languages and discrete controller synthesis, provides means for static enforcement of global properties, such as the avoidance of inconsistent decisions. This work has been done with Éric Rutten, Noël De Palma, and Soguy Mak-Karé Gueye.
Journal Articles
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Designing Autonomic Management Systems by using Reactive Control Techniques
Nicolas Berthier, Éric Rutten, Noël De Palma, Soguy Mak-Karé Gueye. IEEE Transactions on Software Engineering, 42(7):640–657, July 2016.Abstract
The ever growing complexity of software systems has led to the emergence of automated solutions for their management. The software assigned to this work is usually called an Autonomic Management System (AMS). It is ordinarily designed as a composition of several managers, which are pieces of software evaluating the dynamics of the system under management through measurements (e.g., workload, memory usage), taking decisions, and acting upon it so that it stays in a set of acceptable operating states. However, careless combination of managers may lead to inconsistencies in the taken decisions, and classical approaches dealing with these coordination problems often rely on intricate and ad hoc solutions. To tackle this problem, we take a global view and underscore that AMSs are intrinsically reactive, as they react to flows of monitoring data by emitting flows of reconfiguration actions. Therefore we propose a new approach for the design of AMSs, based on synchronous programming and discrete controller synthesis techniques. They provide us with high-level languages for the specification of the system to manage, as well as means for statically guaranteeing the absence of logical coordination problems. Hence, they suit our main contribution, which is to obtain guarantees at design time about the absence of logical inconsistencies in the taken decisions. We detail our approach, illustrate it by designing an AMS for a realistic multi-tier application, and evaluate its practicality with an implementation.
The prototype tool sams demonstrates the concepts introduced in this article.
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Coordinating Self-sizing and Self-repair Managers for Multi-tier Systems
Soguy Mak-Karé Gueye, Noël De Palma, Éric Rutten, Alain Tchana, and Nicolas Berthier. Future Generation Computer Systems, 35(0):14–26, June 2014.Abstract
Computing systems have become more and more distributed and heterogeneous, making their manual administration difficult and error-prone. The Autonomic Computing approach has been proposed to overcome this issue, by automating the administration of computing systems with the help of control loops called autonomic managers. Many research works have investigated the automation of the administration functions of computing systems and today many autonomic managers are available. However the existing autonomic manages are mostly specialized in the management of few administration concerns such as self-repair which handles server failures, and self-sizing which deals with dynamic server allocation. This makes necessary the coexistence of multiple autonomic managers for a complete system management. The coexistence of several such managers is required to handle multiple concerns, yet requires coordination mechanisms to avoid incoherent administration decisions. We investigate the use of control techniques for the design of coordination controllers, for which we exercise synchronous programming that provide formal semantics, and discrete controller synthesis to automate the construction of the controller. The paper details an application of the latter approach for the design of a coordination controller to orchestrate the execution of four self-repair and two self-sizing managers that address the availability and performance of a multi-tier replication-based system. We evaluate and demonstrate the benefits of our coordination solution by executing the RUBiS Benchmark web application.
Applications of Logico-numerical Control
Papers
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Logico-numerical Control for Software Components Reconfiguration
Nicolas Berthier, Frederico Alvares, Hervé Marchand, Gwenaël Delaval, Éric Rutten. In 1st IEEE Conference on Control Technology and Applications, CCTA ’17. IEEE, August 2017.Abstract
We target the problem of the safe control of reconfigurations in component-based software systems, where strategies of adaptation to variations in both their environment and internal resource demands need to be enforced. In this context, the computing system involves software components that are subject to control decisions. We approach this problem under the angle of Discrete Event Systems (DES), involving properties on events observed during the execution (e.g., requests of computing tasks, work overload), and a state space representing different configurations such as activity or assemblies of components. We consider in particular the potential of applying novel logico-numerical control techniques to extend the expressivity of control models and objectives, thereby extending the application of DES in component-based software systems. We elaborate methodological guidelines for the application of logico-numerical control based on a case-study, and validate the result experimentally.
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Towards Applying Logico-numerical Control to Dynamically Partially Reconfigurable Architectures
Nicolas Berthier, Xin An, Hervé Marchand. In 5th Int. Workshop on Dependable Control of Discrete Systems, DCDS ’15. IFAC, May 2015.Abstract
We investigate the opportunities given by recent developments in the context of Discrete Controller Synthesis algorithms for infinite, logico-numerical systems. To this end, we focus on models employed in previous work for the management of dynamically partially reconfigurable hardware architectures. We extend these models with logico-numerical features to illustrate new modeling possibilities, and carry out some benchmarks to evaluate the feasibility of the approach on such models.
Control for Energy Efficient Circuit Designs
Papers
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A Case for Symbolic Limited Optimal Discrete Control: Energy Management in Reactive Data-flow Circuits
Mete Özbaltan and Nicolas Berthier. In 21st IFAC World Congress, IFAC ’20, July 2020. To appear in IFAC-PapersOnLine.Abstract
We present a framework for achieving efficient dynamic management of configurable reactive data-flow circuits subject to global design objectives such as mutual exclusion on shared resources and minimization of energy consumption. We propose a new symbolic controller synthesis algorithm that targets the optimization of a cost function summed over a sliding window of a given number of reactions of the system. We then present a technique for constructing symbolic models of configurable data-flow circuits that lends itself to the automatic computation of dynamic configuration controllers. We use these models to experimentally evaluate our control algorithm, and make the case for symbolic optimal discrete controller synthesis on such designs.
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Exercising Symbolic Discrete Control for Designing Low-power Hardware Circuits: an Application to Clock-gating
Mete Özbaltan and Nicolas Berthier. In 14th Int. Workshop on Discrete Event Systems, WODES ’18, pages 120–126. IFAC, June 2018.Abstract
We devise a tool-supported framework for achieving power-efficiency of hardware chips from high-level designs described using the popular hardware description language Verilog. We consider digital circuits as hierarchical compositions of sub-circuits, and achieve power-efficiency by switching-off the clock of each sub-circuit according to some clock-gating logic. We encode the computation of the latter as several small symbolic discrete controller synthesis problems, and use the resulting controllers to derive power-efficient versions from original circuit designs. We detail and illustrate our approach using a running example, and validate it experimentally by deriving a low-power version of an actual Reed-Solomon decoder.
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