Fault-recovery and Coherence in Internet of Things Choreographies

International audienceFacilitating the creation of applications for the Internet of Things (IoT) is a major concern to increase the development of the IoT. Due to devices heterogeneity, programmers have to find solutions that hide hardware diversity. D-LITe, our previous work, is a framework that introduces genericity by providing a universal programming interface for any Object. In D-LITe, Objects are dynamically configured to have their own behaviour, and their actions/reactions are considered as part of a whole application. D-LITeful Objects offer a REST web service that describes their capabilities, receives the application logic to be executed, and interacts with other stakeholders. Then, the complete application is seen as choreography of Object behaviours. But the main issue of choreographies is the loss of coherence. Because of their unreliability, some networks used in IoT may introduce de-synchronization between Objects behaviours, leading to interactions errors and failures. In this paper, we propose a solution to reintroduce coherence among the different stakeholders implied in the application, in order to keep the advantages of choreography while dealing with this main issue. An overlay of logical checkpoints at the application layer defines the dependences between the coherent states of a set of objects and triggers re-synchronization messages. Correcting statements are thus spread through the network, which enables fault recovery in the choreography. This paper ends with a discussion on the trade-off between the checking cost and the reliability improvement