Section: New Results

Dynamic Adaptation of Service-based Applications

Participants : Djawida Dib, Erwan Daubert, Guillaume Gauvrit, André Lage, Christine Morin, Nikos Parlavantzas, Jean-Louis Pazat, Chen Wang.

Adaptation for Service-Oriented Architectures

Participants : Erwan Daubert, Guillaume Gauvrit, André Lage, Nikos Parlavantzas, Jean-Louis Pazat, Chen Wang.

Service-Oriented Computing is a paradigm that is rapidly spreading in all application domains and all environments - grids, clusters of computers, mobile and pervasive platforms. The following works take place in the context of the S-Cube European Network of Excellence.

Services adaptation in distributed and heterogeneous systems

Participants : Erwan Daubert, Guillaume Gauvrit, Jean-Louis Pazat.

We are still studying service adaptation in distributed and heterogeneous systems. This work covers different aspects such as structural, behavioral and environmental adaptation, distributed decision and planification of adaptation actions, adaptive allocation of resources for services. A framework called SAFDIS for "Self Adaptation For Distributed Services" has been defined and implemented. It is built as a set of services, providing functionalities useful to build an adaptation system. The analysis phase can take reactive as well as proactive decisions. This gives the ability to either react fast or to take decisions for the long term. This implies the ability to analyze the context with a variable depth of reasoning. Our implementation of the SAFDIS analysis phase also distributes and decentralizes its analysis process to spread the computational load and make the analysis process scalable. The planning phase seeks the set of actions (the plan) needed to adapt the system according to the strategy chosen by the analysis phase. It also schedules the selected actions to ensure a coherent and efficient execution of the adaptation. The planning topic is a well known subject in AI research works and many algorithms already exist in that field to produce efficient schedules. With our SAFDIS framework, the planning phase is able to reuse these algorithms. The resulting plan of actions can have actions that can be executed in parallel.

Quality Assurance for Distributed Services

Participants : André Lage, Nikos Parlavantzas, Jean-Louis Pazat.

In the context of the service-centric paradigm, we have designed and developed the Qu4DS (Quality Assurance for Distributed Services) system. Qu4DS is a cloud PaaS solution which fills the gap between SaaS service providers and IaaS infrastructures. Qu4DS provides automatic support for service execution management, aiming at increasing service providers' profits by reducing resource costs as well as fines owning to SLA violations. More specifically, Qu4DS dynamically acquires resources according to the customer demand, deploys service instances and implements QoS assurance mechanisms in order to prevent SLA violations. Qu4DS has been evaluated on Grid'5000 and shown to be effective in reducing service provider's costs [33] . This work has been done in the context of André Lage-Freitas' PhD thesis [10] .

Self-configuration for Cloud Platforms

Participants : Jean-Louis Pazat, Chen Wang.

By definition, cloud computing offers an abstraction to manage various needs and concepts such as distributed software design, the deployment of such software on dynamic resources and the management of this kind of resources. Thus it is possible to reconfigure (adapt) according to some needs the software as well as the use of the resources. However these reconfigurations that are used on different layers may also have impacts on the others. Moreover these layers are independent and so are able to adapt themselves independently of the others. In our work, we propose to use some adaptation capabilities offered for example by the infrastructure (IaaS) that manages the resources to adapt the software (SaaS). We also propose to use planning algorithms to coordinate the adaptations between them to avoid inconsistency or inefficiency due to concurrent adaptations.

Dynamic Adaptation of Chemical services

Participants : Jean-Louis Pazat, Chen Wang.

We have proposed a QoS-aware middleware for dynamic service execution. In the context of dynamic execution, a workflow is defined by composing a set of abstract activities as place holders. Each activity is bound to a suitable partner service, which is selected at run-time from a set of functional equivalent candidates with different non-functional properties such as quality of service (QoS). The service selection process is modeled as a series of chemical reactions. This year, we have studied and implemented fragment replacement in workflows within this environment.

Multi-level Adaptation for Distributed Operating Systems

Participants : Djawida Dib, Christine Morin, Nikos Parlavantzas.

This work focused on enhancing distributed operating systems with the ability to continually adapt to their changing environments. Two challenges arise in this context: how to design the distributed operating system (OS) in order to facilitate dynamic adaptation, and how to ensure that OS-level adaptation does not conflict with application-level adaptation. This work proposed to address these challenges by (1) building the distributed OS as an assembly of adaptable services following the service-oriented architecture; and (2) using a common multi-level adaptation framework to adapt both the OS and the application layers in a coordinated way. To demonstrate the usefulness of the proposed architecture, the work focused on distributed shared memory services and provided examples and experimental results using the Kerrighed distributed OS. The work was performed as part of Djawida Dib's thesis [22] .