Components are widely used for managing distributed applications because they not only capture the software architecture of managed applications as an assembly of components but also permit to dynamically adapt these applications to changing environments. Following this approach, our practical experience in the Jade environment about developing an autonomic repair management service with a self-healing behavior shows novel requirements on reflective component models for architecture-based management systems. First, we have identified five essential runtime abstractions that a component model must include in order to efficiently support an autonomic repair service. Second, our experience suggests that traditional reflective component models should be extended to allow specializing meta-operations. Third, our experience also shows that a meta-data checkpointing capability is best-suited for meta-data recovery after failures. We demonstrate the soundness of these findings in several ways. We applied the difficult problem of autonomic repair to both J2EE and JMS middleware. We further stressed our algorithms and mechanisms by applying them recursively towards gaining a self-healing property for the repair service itself. Although our experience was done in the Jade context, using the Fractal component model, we believe our findings to be general to architecture-based management systems using reflective component models.

In this paper, we propose a reconfiguration protocol that can handle any number of failures during a reconfiguration, always producing an architecturally-consistent assembly of components that can be safely introspected and further reconfigured. Our protocol is based on the concept of Incrementally Consistent Sequences (ICS), ensuring that any reconfiguration incrementally respects the reconfiguration contract given to component developers: reconfiguration grammar and architectural invariants. We also propose two recovery policies, one rolls back the failed reconfiguration and the other rolls it forward, both going as far as possible, failure permitting. We specified and proved the reconfiguration contract, the protocol, and recovery policies in Coq.

International audienceIn the field of cloud computing, current solutions dedicated to PaaS (Platform as a Service), i.e. the environments that deal with the different stages of the application life-cycle, remain business domain specific and are only partially automated. This limitation is due to the lack of an architectural model for describing a distributed application in terms of its software stacks (operating system, middleware, application), their instantiation as virtual machines, and their configuration interdependencies. This article puts forward (i) a component-based application model for defining any kind of distributed applications composed of a set of interconnected virtual machines, (ii) an automated line for deploying such a distributed application in the cloud, which includes a decentralized protocol for self-configuring the virtual application machines, (iii) a first performance evaluation demonstrating the viability of the solution