Manipulating Managed Execution Runtimes to Support Self-Healing Systems

Self-healing systems require that repair mechanisms are available to resolve problems that arise while the system executes. Managed execution environments such as the Common Language Runtime (CLR) and Java Virtual Machine (JVM) provide a number of application services (application isolation, security sandboxing, garbage collection and structured exception handling) which are geared primarily at making managed applications more robust. However, none of these services directly enables applications to perform repairs or consistency checks of their components. From a design and implementation standpoint, the preferred way to enable repair in a self-healing system is to use an externalized repair/adaptation architecture rather than hardwiring adaptation logic inside the system where it is harder to analyze, reuse and extend. We present a framework that allows a repair engine to dynamically attach and detach to/from a managed application while it executes essentially adding repair mechanisms as another application service provided in the execution environment

Optimizing decomposition of software architecture for local recovery

Cataloged from PDF version of article.The increasing size and complexity of software systems has led to an amplified number of potential failures and as such makes it harder to ensure software reliability. Since it is usually hard to prevent all the failures, fault tolerance techniques have become more important. An essential element of fault tolerance is the recovery from failures. Local recovery is an effective approach whereby only the erroneous parts of the system are recovered while the other parts remain available. For achieving local recovery, the architecture needs to be decomposed into separate units that can be recovered in isolation. Usually, there are many different alternative ways to decompose the system into recoverable units. It appears that each of these decomposition alternatives performs differently with respect to availability and performance metrics. We propose a systematic approach dedicated to optimizing the decomposition of software architecture for local recovery. The approach provides systematic guidelines to depict the design space of the possible decomposition alternatives, to reduce the design space with respect to domain and stakeholder constraints and to balance the feasible alternatives with respect to availability and performance. The approach is supported by an integrated set of tools and illustrated for the open-source MPlayer software

Prestige, Performance and Social Pressure in Viral Challenge Memes: Neknomination, the Ice-Bucket Challenge and SmearForSmear as Imitative Encounters

This article examines social media challenges that emerged in 2013, focusing on Neknomination, the Ice-Bucket Challenge and SmearForSmear. We understand them as ‘viral challenge memes’ that manifest a set of consistent features, making them a distinctive phenomenon within digital culture. Drawing upon Tarde’s concept of the imitative-encounter, we highlight three central features: their basis in social belonging and participation; the role of prestigious people and groups in determining the spread of challenges; and the distinctive techniques of self-presentation undertaken by participants. Based upon focus group interviews, surveys and visual analysis we suggest that viral challenge memes are social practices that diffuse in a wave-like fashion. Negotiating tensions between the social and individual, imitation and innovation, continuity and change, viral challenge memes are best thought of as creative practices, rather than sheep-like acts of conformity, and affirm the usefulness of analytical principles drawn from Tarde

Monadology and ethnography: Towards a Tardian monadic

This article outlines the project of a ‘monadic ethnography’ based on Gabriel Tarde’s monadology. Tarde’s key contention is that ‘everything is a society’, i.e. that the world is made up of composite and relational entities of infinitesimal complexity called monads. These assemblages of heterogeneous elements engaged in relations of mutual possession constitute the object of study of ‘monadic ethnography’. Their analysis, in turn, has a series of methodological and formal implications, including a transformation of concepts of scale, spatiality and temporality and the need to find representational strategies suitable for conveying the monads’ dynamic qualities. A fieldwork example which discusses the making of a car part in a small workshop based in the Can Ricart factory in Barcelona is provided. Throughout the article, the idea of ‘monadic ethnography’ is discussed in relation to the recent rediscovery of Tarde’s work, the work of Bruno Latour and Gilles Deleuze, and the so-called ‘ontological turn’ in the social sciences

Conformal and continuous deposition of bifunctional cobalt phosphide layers on p-silicon nanowire arrays for improved solar hydrogen evolution

Vertically aligned p-silicon nanowire (SiNW) arrays have been extensively investigated in recent years as promising photocathodes for solar-driven hydrogen evolution. However, the fabrication of SiNW photocathodes with both high photoelectrocatalytic activity and long-term operational stability using a simple and affordable approach is a challenging task. Herein, we report conformal and continuous deposition of a di-cobalt phosphide (Co2P) layer on lithography-patterned highly ordered SiNW arrays via a cost-effective drop-casting method followed by a low-temperature phosphorization treatment. The as-deposited Co2P layer consists of crystalline nanoparticles and has an intimate contact with SiNWs, forming a well-defined SiNW@Co2P core/shell nanostructure. The conformal and continuous Co2P layer functions as a highly efficient catalyst capable of substantially improving the photoelectrocatalytic activity for the hydrogen evolution reaction (HER) and effectively passivates the SiNWs to protect them from photo-oxidation, thus prolonging the lifetime of the electrode. As a consequence, the SiNW@Co2P photocathode with an optimized Co2P layer thickness exhibits a high photocurrent density of -21.9 mA.cm(-2) at 0 V versus reversible hydrogen electrode and excellent operational stability up to 20 h for solar-driven hydrogen evolution, outperforming many nanostructured silicon photocathodes reported in the literature. The combination of passivation and catalytic functions in a single continuous layer represents a promising strategy for designing high-performance semiconductor photoelectrodes for use in solar-driven water splitting, which may simplify fabrication procedures and potentially reduce production costsThis work was funded by ERDF funds through the Portuguese Operational Programme for Competitiveness and Internationalization COMPETE 2020, and national funds through FCT – The Portuguese Foundation for Science and Technology, under the project “PTDC/CTM-ENE/2349/2014” (Grant Agreement No. 016660). The work is also partially funded by the Portugal-China Bilateral Collaborative Programme (FCT/21102/28/12/2016/S). L. F. Liu acknowledges the financial support of the FCT Investigator Grant (IF/01595/2014) and Exploratory Grant (IF/01595/2014/CP1247/CT0001). L. Qiao acknowledges the financial support of the Ministry of Science and Technology of China (Grant Agreement No. 2016YFE0132400).info:eu-repo/semantics/publishedVersio

Recursive restartability: turning the reboot sledgehammer into a scalpel

Even after decades of software engineering research, complex computer systems still fail, primarily due to nondeterministic bugs that are typically resolved by rebooting. Conceding that Heisenbugs will remain a fact of life, we propose a systematic investigation of restarts as "high availability medicine." In this paper we show how recursive restartability (RR) - the ability of a system to gracefully tolerate restarts at multiple levels improves fault tolerance, reduces time-to-repair and enables system designers to build flexible, highly available software infrastructures. Using several examples of widely deployed software systems, we identify properties that are required of RR systems and outline an agenda for turning the recursive restartability philosophy into a practical software structuring tool. Finally, we describe infrastructural support for RR systems, along with initial ideas on how to analyze and benchmark such system