Cédric Tedeschi

Decentralized Approach for Execution of Composite Web Services Using the Chemical Paradigm

Nowadays, executions of composite Web services are typically conducted by heavyweight centralized engines. A centralized is a potential processing and communication bottleneck as well as a central point of failure, and its cost of deployment is usually too high for a large number of small businesses or end-users. In addition, it presents some weaknesses dealing with privacy issues. These drawbacks, and requirements such as loose coupling, are pushing service infrastructures toward more decentralized and dynamic interaction schemes. In this paper, we propose a decentralized alternative system for the execution of composite Web services based on the chemical analogy. The chemical paradigm provides a high-level execution model that allows executing composite services in a fully decentralized manner. Our architecture is composed by nodes communicating through a shared space containing both control and data flows, allowing to distribute the composition among nodes without the need for any centralized coordination.

A Chemistry-Inspired Workflow Management System for Scientific Applications in Clouds

With the proliferation of Web Services, scientific applications are more and more designed as temporal compositions of services, commonly referred to as, workflows. To address this paradigm shift, different workflow management systems have been proposed. If their efficiency has been established over centralized reliable systems, it is questionable over highly decentralized failure-prone platforms. Scientific applications recently started to be deployed over clouds, leading to new issues, like elasticity, i.e., the possibility to dynamically refine, at runtime, the amount of resources dedicated to an application. This raised a new demand for programming models, able to express autonomic self-coordination of services in a dynamic, elastic platform. Chemistry-inspired computing recently regained momentum in this context, naturally expressing parallelism, distribution, and autonomic behaviors. While its high expressiveness and adequacy for this context has been established, the chemical model severely suffers from a lack of proof of concepts. In this paper, we concretely show how to leverage such models in this context. We focus on the design, the implementation and the experimental validation of a chemistry-inspired scientific workflow management system.

A Chemistry-Inspired Workflow Management System for Decentralizing Workflow Execution

With the recent widespread adoption of service-oriented architecture, the dynamic composition of services is now a crucial issue in the area of distributed computing. The coordination and execution of composite Web services are today typically conducted by heavyweight centralized workflow engines, leading to an increasing probability of processing and communication bottlenecks and failures. In addition, centralization induces higher deployment costs, such as the computing infrastructure to support the workflow engine, which is not affordable for a large number of small businesses and end-users. In a world where platforms are more and more dynamic and elastic as promised by cloud computing, decentralized and dynamic interaction schemes are required. Addressing the characteristics of such platforms, nature-inspired analogies recently regained attention to provide autonomous service coordination on top of dynamic large scale platforms. In this paper, we propose an approach for the decentralized execution of composite Web services based on an unconventional programming paradigm that relies on the chemical metaphor. It provides a high-level execution model that allows executing composite services in a decentralized manner. Composed of services communicating through a persistent shared space containing control and data flows between services, our architecture allows to distribute the composition coordination among nodes. A proof of concept is given, through the deployment of a software prototype implementing these concepts, showing the viability of an autonomic vision of service composition.

Beyond the Clouds: How Should Next Generation Utility Computing Infrastructures Be Designed?

To accommodate the ever-increasing demand for Utility Computing (UC) resources while taking into account both energy and economical issues, the current trend consists in building even larger data centers in a few strategic locations. Although, such an approach enables to cope with the actual demand while continuing to operate UC resources through centralized software system, it is far from delivering sustainable and efficient UC infrastructures. In this scenario, we claim that a disruptive change in UC infrastructures is required in the sense that UC resources should be managed differently, considering locality as a primary concern. To this aim, we propose to leverage any facilities available through the Internet in order to deliver widely distributed UC platforms that can better match the geographical dispersal of users as well as the unending resource demand. Critical to the emergence of such locality-based UC (LUC) platforms is the availability of appropriate operating mechanisms. We advocate the implementation of a unified system driving the use of resources at an unprecedented scale by turning a complex and diverse infrastructure into a collection of abstracted computing facilities that is both easy to operate and reliable. By deploying and using such a LUC Operating System on backbones, our ultimate vision is to make possible to host/operate a large part of the Internet by its internal structure itself: a scalable and nearly infinite set of resources delivered by any computing facilities forming the Internet, starting from the larger hubs operated by ISPs, governments, and academic institutions to any idle resources that may be provided by end users.

Rule-driven service coordination middleware for scientific applications

With the proliferation of Web services, scientific applications are more and more designed as temporal compositions of services, commonly referred to as workflows. To address this paradigm shift, different workflow management systems have been proposed. While their efficiency has been established over centralized static systems, it is questionable over decentralized failure-prone platforms. Scientific applications recently started to be deployed over large distributed computing platforms, leading to new issues, like elasticity, i.e., the possibility to dynamically refine, at runtime, the amount of resources dedicated to an application. This raised again the demand for new programming models, able to express autonomic self-coordination of services in a dynamic platform. Nature-inspired, rule-based computing models recently gained a lot of attention in this context. They are able to naturally express parallelism, distribution, and autonomic adaptation. While their high expressiveness and adequacy for this context has been established, such models severely suffer from a lack of proof of concepts. In this paper, we concretely show how to leverage such models in this context. We focus on the design, the implementation and the experimental validation of a chemistry-inspired scientific workflow management system.

Combining workflow templates with a shared space-based execution model

The growth for scientific data has led to data analysis being a critical step in the scientific process. The next generation scientific data analysis environment needs to address two challenges i) productivity of the end-user and ii) scalability of the workflows. The need to ensure both goals requires us to revisit the design and implementation of workflow tools. In this paper, we study the interaction of Tigres and HOCL-TS towards meeting these goals. Tigres and HOCL-TS have evolved separately; however their complementary foci allows us to study these issues in greater detail. We describe the pros and cons of an approach that integrates Tigres and HOCL-TS and HOCL-TS extension to support common non-functional requirements such as logging and monitoring that can be made available to the users through the Tigres API.

When self-stabilization meets real platforms: An experimental study of a peer-to-peer service discovery system

In the days of large scale, heterogeneous computing infrastructures gathering myriads of services, service discovery has become a critical feature that has to deal with the scale and dynamic nature of such platforms. The Spades project (Servicing Petascale Architectures and DistributEd System, 08-ANR-SEGI-025) is a consortium whose purpose is to promote new solutions to deal with a very large number of volatile and heterogeneous computing resources. For the aforementioned reasons, at the projects core, the service discovery has been envisioned as fully decentralized. More precisely, the proposed P2P service discovery system proposed within the Spades project is based on the Dlpt approach (Distributed Lexicographic Placement Table) providing distributed structures and algorithms for such a feature. In this paper, an implementation of the Dlpt concepts into the middleware developed within the Spades project, called Sbam (Spades BAsed Middleware), is devised. Furthermore, its actual deployment over a nation-wide grid system, as well as its performance are detailed.

Simulating awareness in global software engineering: a comparative analysis of scrum and agile service networks

Global software engineering (GSE) is a business strategy to realize a business idea (i.e. the development project) faster, through round-the-clock productivity. However, GSE creates a volatile and unstable process in which many actors interact together against unpredictable premises (e.g. cultural or time differences), often producing unexpected outcomes (e.g. compacting effects of distance and time). So far, Scrum has been used extensively for embarking in global software engineering, but many of the problems in Scrum-based GSE could still benefit from the usage of ad-hoc supporting tools (e.g. information continuity between timezones, cultural differences, developers awareness, etc.). Agile Service Networks (ASNs) are networks of service oriented applications (nodes) that collaborate adaptively towards a common goal. ASNs offer a way to represent GSE professionals through service-oriented “social” nodes in a “small-world” network (much like a Facebook for a specific GSE project). This paper presents a comparison between the two approaches, namely Scrum and ASNs, to determine ASNs potentials as mechanisms to maintain awareness in GSE.

Implementation and Evaluation of a P2P Service Discovery System: Application in a Dynamic Large Scale Computing Infrastructure

At times of large scale, heterogeneous computing infrastructures gathering myriads of services, service discovery has become a critical feature that has to deal with the scale and dynamic nature of such platforms. The SPADES project (Servicing Petascale Architectures and Distributed System) is a consortium whose purpose is to promote new solutions to deal with distributed, volatile and heterogeneous computing resources. For the aforementioned reasons, at the projects core, the service discovery has been envisioned as fully decentralized. More precisely, the proposed P2P service discovery system proposed within the SPADES project is based on the DLPT approach (Distributed Lexicographic Placement Table) providing distributed structures and algorithms for such a feature. In this paper, an implementation of the DLPT concepts into the middleware developed within the SPADES project, called SBAM, is devised. Moreover, its actual deployment over a nation-wide grid system, as well as its performance are detailed.

GinFlow: A Decentralised Adaptive Workflow Execution Manager

Workflow-based computing has become a dominant paradigm to design and execute scientific applications. After the initial breakthrough of now standard workflow management systems, several approaches have recently proposed to decentralise the coordination of the execution. In particular, shared space-based coordination has been shown to provide appropriate building blocks for such a decentralised execution. Uncertainty is also still a major concern in scientific workflows. The ability to adapt the workflow, change its shape and switch for alternate scenarios on-the-fly is still missing in workflow management systems. In this paper, based on a shared space approach, we firstly devise a programmatic way to specify such adaptive workflows. We use a reactive, rule-based programming model to modify the workflow description by changing its associated direct acyclic graph on-the-fly without needing to stop and restart the execution from the beginning. Secondly, we present the GinFlow middleware, a resilient decentralised workflow execution manager implementing these concepts. Through a set of deployments of adaptive workflows of different characteristics, we discuss the GinFlow performance and resilience and show the limited overhead of the adaptiveness mechanism, making it a promising decentralised adaptive workflow execution manager.