An asynchronous, decentralised commitment protocol for semantic optimistic replication

We study large-scale distributed cooperative systems that use optimistic replication. We represent a system as a graph of actions (operations) connected by edges that reify semantic constraints between actions. Constraint types include conflict, execution order, dependence, and atomicity. The local state is some schedule that conforms to the constraints; because of conflicts, client state is only tentative. For consistency, site schedules should converge; we designed a decentralised, asynchronous commitment protocol. Each client makes a proposal, reflecting its tentative and{\slash}or preferred schedules. Our protocol distributes the proposals, which it decomposes into semantically-meaningful units called candidates, and runs an election between comparable candidates. A candidate wins when it receives a majority or a plurality. The protocol is fully asynchronous: each site executes its tentative schedule independently, and determines locally when a candidate has won an election. The committed schedule is as close as possible to the preferences expressed by clients

Semantic Middleware for Designing Collaborative Applications in Mobile Environment

International audienceThe Telex middleware facilitates the design of collaborative applications in a mobile environment. It provides optimistic replication, tentative execution and disconnected work. It solves conflicts based on semantic information provided by applications. We study in particular a Shared Calendar (SC) application, whereby mobile users can create and manage meetings in a collection of shared calendars. The application provides Telex with objects representing (1) meeting creation and modification operations (actions), (2) dependence or conflict information between actions (constraints). When a conflict occurs, Telex proposes solutions to users. The advantage of this approach is a clean separation of concerns. The SC application writer concentrates on application logic, whereas Telex takes care of replication, consistency, conflicts, and commitment across all applications

Telex: A Semantic Platform for Cooperative Application Development

International audienceDeveloping write-sharing applications is challenging. Remote and offline data sharing are increasingly important. We propose a generic platform called Telex to ease development and to provide guarantees. Telex is driven by application semantics. Telex takes care of replication and persistence, drives application progress, and ensures that replicas eventually agree on a correct, common state. We show by example how application design proceeds from high-level application invariants to application-provided parameters that guides Telex. The main data structure of Telex is a large, replicated, highly dynamic graph; we discuss the engineering trade-offs for such a graph and our solutions. Finally, we report an experimental evaluation of Telex based on a cooperative calendar application and on benchmarks

An Asynchronous, Decentralised Commitment Protocol for Semantic Optimistic Replication

apport de recherche ISSN 0249-6399 ISRN INRIA/RR--6069--FR+ENG Un protocole de validation pour la réplication optimiste dans les systèmes répartis sémantiquement riches Résumé: Nous examinons à travers ce document la cohérence dans les systèmes répartis répliquant des données de manière optimiste. Le paradigme de la réplication optimiste est que les sites composant le système réparti peuvent ré-éxecuter les requêtes des clients (actions) si la sémantique liant les actions le nécessite. Dans de tels systèmes le critère de cohérence est que les sites convergent à terme vers des exécutions équivalentes. Afin d’assurer cette convergence, un protocole de validation est nécessaire. C’est l’objet de cette étude. Notre protocole procède par éléctions successives sur des ensembles d’actions exécutées de manière optimiste par le système. La sémantique prise en compte dans ce protocole est suffisament riche pour exprimer des notions telles que la non-commutativité, le conflit ou encore la causalité entre les actions. Nous prouvons que notre protocole est sûr, et ce en dépit des éventuelles pannes franches pouvant survenir sur les sites. Mots-clés: réplication optimiste, validation, protocoles de vote An asynchronous, decentralised commitment protocol for semantic optimistic replication 3