Aligning component upgrades

Modern software systems, like GNU/Linux distributions or Eclipse-based development environment, are often deployed by selecting components out of large component repositories. Maintaining such software systems by performing component upgrades is a complex task, and the users need to have an expressive preferences language at their disposal to specify the kind of upgrades they are interested in. Recent research has shown that it is possible to develop solvers that handle preferences expressed as a combination of a few basic criteria used in the MISC competition, ranging from the number of new components to the freshness of the final configuration. In this work we introduce a set of new criteria that allow the users to specify their preferences for solutions with components aligned to the same upstream sources, provide an efficient encoding and report on the experimental results that prove that optimising these alignment criteria is a tractable problem in practice.Comment: In Proceedings LoCoCo 2011, arXiv:1108.609

Dynamic software updates for real-time systems

Seamlessly updating software in running systems has re-cently gained momentum. Dynamically updating the soft-ware of real-time embedded systems, however, still poses numerous challenges: such systems must meet hard dead-lines, cope with limited resources, and adhere to high safety standards. This paper presents a solution for updating component-based cyclic embedded systems without violating real-time constraints. In particular, it investigates how to identify points in time at which updates can be performed and how to transfer the state of a component to a new version of the same component. We also present experimental results to validate the proposed solution

Run-time Variability with First-class Contexts

Software must be regularly updated to keep up with changing requirements. Unfortunately, to install an update, the system must usually be restarted, which is inconvenient and costly. In this dissertation, we aim at overcoming the need for restart by enabling run-time changes at the programming language level. We argue that the best way to achieve this goal is to improve the support for encapsulation, information hiding and late binding by contextualizing behavior. In our approach, behavioral variations are encapsulated into context objects that alter the behavior of other objects locally. We present three contextual language features that demonstrate our approach. First, we present a feature to evolve software by scoping variations to threads. This way, arbitrary objects can be substituted over time without compromising safety. Second, we present a variant of dynamic proxies that operate by delegation instead of forwarding. The proxies can be used as building blocks to implement contextualization mechanisms from within the language. Third, we contextualize the behavior of objects to intercept exchanges of references between objects. This approach scales information hiding from objects to aggregates. The three language features are supported by formalizations and case studies, showing their soundness and practicality. With these three complementary language features, developers can easily design applications that can accommodate run-time changes

Rebuilding Debian using Distributed Computing

International audienceDoing Quality Assurance work on Debian, a Linux distribution with more than 12000 packages, requires an impressive amount of computing power, which is usually not available for its developers. In this article, we report on the development of an infrastructure to run quality-assurance tasks on Debian using the Grid'5000 experimental platform. In particular, we focus on the problem of rebuilding all packages in Debian from source. We describe the details of this task, and the infrastructure we developed, with scalability and robustness in mind. The results we obtained are then presented, and we discuss possible improvements and lessons we learnt in the process, which might be useful in the context of other large-scale experiments

Shortening Time-to-Discovery with Dynamic Software Updates for Parallel High Performance Applications

Despite using multiple concurrent processors, a typical high performance parallel application is long-running, taking hours, even days to arrive at a solution. To modify a running high performance parallel application, the programmer has to stop the computation, change the code, redeploy, and enqueue the updated version to be scheduled to run, thus wasting not only the programmer’s time, but also expensive computing resources. To address these inefficiencies, this article describes how dynamic software updates can be used to modify a parallel application on the fly, thus saving the programmer’s time and using expensive computing resources more productively. The net effect of updating parallel applications dynamically reduces their time-to-discovery metrics, the total time it takes from posing a problem to arriving at a solution. To explore the benefits of dynamic updates for high performance applications, this article takes a two-pronged approach. First, we describe our experience in building and evaluating a system for dynamically updating applications running on a parallel cluster. We then review a large body of literature describing the existing state of the art in dynamic software updates and point out how this research can be applied to high performance applications. Our experimental results indicate that dynamic software updates have the potential to become a powerful tool in reducing the time-to-discovery metrics for high performance parallel applications

Scheduling Dynamic Software Updates in Mobile Robots

We present NeRTA (Next Release Time Analysis), a technique to enable dynamic software updates for low-level control software of mobile robots. Dynamic software updates enable software correction and evolution during system operation. In mobile robotics, they are crucial to resolve software defects without interrupting system operation or to enable on-the-fly extensions. Low-level control software for mobile robots, however, is time sensitive and runs on resource-constrained hardware with no operating system support. To minimize the impact of the update process, NeRTA safely schedules updates during times when the computing unit would otherwise be idle. It does so by utilizing information from the existing scheduling algorithm without impacting its operation. As such, NeRTA works orthogonal to the existing scheduler, retaining the existing platform-specific optimizations and fine-tuning, and may simply operate as a plug-in component. To enable larger dynamic updates, we further conceive an additional mechanism called bounded reactive control and apply mixed-criticality concepts. The former cautiously reduces the overall control frequency, whereas the latter excludes less critical tasks from NeRTA processing. Their use increases the available idle times. We combine real-world experiments on embedded hardware with simulations to evaluate NeRTA. Our experimental evaluation shows that the difference between NeRTA’s estimated idle times and the measured idle times is less than 15% in more than three-quarters of the samples. The combined effect of bounded reactive control and mixed-criticality concepts results in a 150+% increase in available idle times. We also show that the processing overhead of NeRTA and of the additional mechanisms is essentially negligible

TOWARDS CHANGE VALIDATION IN DYNAMIC SYSTEM UPDATING FRAMEWORKS

Dynamic Software Updating (DSU) provides mechanisms to update a program without stopping its execution. An indiscriminate update that does not consider the current state of the computation, potentially undermines the stability of the running application. Determining automatically a safe moment, the time that the updating process could be started, is still an open crux that usually neglected from the existing DSU systems. The program developer is the best one who knows the program semantics and the logical relations between two successive versions as well as the constraints which should be respected in order to proceed with the update. Therefore, a set of meta-data has been introduced that could be exploited to explain the constraints of the update. These constraints should be considered at the dynamic update time. Thus, a runtime validator has been designed and implemented to verify these constraints before starting the update process. The validator is independent of existing DSU systems and can be plugged into DSUs as a pre-update component. An architecture for validation has been proposed that includes the DSU, the running program, the validator, and their communications. Along with the ability to describe the restrictions by using meta-data, a method has been presented to extract some constraints automatically. The gradual transition from the old version to the new version requires that the running application frequently switches between executing old and new code for a transient period. Although this swinging execution phenomenon is inevitable, its beginning can be selected. Considering this issue, an automatic method has been proposed to determine which part of the code is unsafe to participate in the swinging execution. The method has been implemented as a static analyzer which can annotate the unsafe part of the code as constraints. This approach is demonstrated in the evolution of the various versions of three different long-running software systems and compared to other approaches. Although the approach has been evaluated by evolving various programs, the impact of different changes in the dynamic update is not entirely clear. In addition, the study of the effect of these changes can identify code smells on the program, regarding the dynamic update issue. For the first time, the code smells have been introduced that may cause a run-time or syntax error on the dynamic update process. A set of candidate error-prone patterns has been developed based on programming language features and possible changes for each item. This set of 75 patterns is inspected by three distinct DSUs to identify problematic cases as code smells. Additionally, error- prone patterns set can be exploited as a reference set by other DSUs to measure own flexibility

Du génie logiciel pour déployer, gérer et reconfigurer les logiciels

As a discipline, software engineering embraces various schools of thought, yet remains consistent with respect to its objective. It aims at providing means for effective and inexpensive production of software by contributing mathematical frameworks, methods and tools. Consequently, we witness some automation in software production process that, as of today, allows producing astronomical amounts of lines of code daily. This rapidly and massively produced software is required for all computer equipment that has invaded our daily life in various forms of other devices (PC, tablet, phone, refrigerator, car, etc.). In this world of large software consumption, it is somewhat surprising that the management of software, after its production, remains dominated by manual practices like searching in lists, downloading units and manual installations. In this context, I organized my research activities such that they aim at providing mathematical frameworks, methods and tools to deploy, distribute or update massive amounts of software since 2001, the year of my PhD defense. These research activities were mainly conducted in Brest at the CS department of Telecom Bretagne as part of the PASS team of IRISA. This document puts into perspective my various scientific contributions, undertaken projects, endeavors in training research students and efforts invested as a teacher. My scientific contributions can be divided into five parts: mathematical models and algorithms for dependency management in software deployment; software component models; processes and tools for massive software deployment; dynamic update of programs at runtime; languages for the design and implementation of software development processes. All these works complement each other, thus making it possible to imagine the proposition of methods and tools for large-scale software deployment.Le génie logiciel est une discipline constituée de nombreux courants mais cohérente par l'objectif affiché. Il s'agit d'aider à la production, de manière efficace et peu coûteuse, de logiciels en offrant des cadres mathématiques, des méthodes et des outils. Ainsi, on a pu assister à une certaine industrialisation du processus de production de logiciel qui permet aujourd'hui de produire, chaque jour, des quantités astronomiques de logiciel. Ce logiciel produit rapidement et en grande quantité est nécessaire pour tous les équipements informatiques qui ont envahi notre quotidien (ordinateur, tablette, téléphone, réfrigérateur, voiture, ...). Dans ce monde de grande consommation du logiciel, il est cependant surprenant de constater que la gestion des logiciels après leur production est resté dominé par des pratiques manuelles de recherche dans des listes, de téléchargement unitaire et d'installation manuelle. C'est dans ce cadre que j'ai développé une activité de recherche visant à fournir des cadres mathématiques, des méthodes et des outils pour déployer, diffuser ou mettre à jour massivement les logiciels depuis 2001 année de ma soutenance de thèse. Ces activités de recherche ont été conduites principalement à Brest au sein du département informatique de Télécom Bretagne dans le cadre de l'équipe PASS de l'IRISA. Mon Habilitation à Diriger des Recherches est l'occasion de remettre en perspective mes différentes contributions scientifiques, les étudiants formés à la recherche, les projets réalisés ainsi que mon investissement en tant qu'enseignant. Les contributions scientifiques peuvent être classées en cinq parties : - des modèles mathématiques et les algorithmes associés pour la gestion des dépendances de logiciels lors de leur déploiement ; - les modèles de composants logiciels ; - les processus et outils pour le déploiement de logiciel massif ; - la mise à jour de programmes sans interrompre leur exécution ; - des langages pour la conception et la réalisation de processus de développement logiciel. Tous ces travaux qui se nourrissent et se complètent permettent d'imaginer la proposition de méthodes et outils pour passer à l'échelle dans la gestion du déploiement des logiciels