When orchestrating highly distributed and data-intensive Web service workflows the geographical placement of the orchestration engine can greatly affect the overall performance of a workflow. Orchestration engines are typically run from within an organisations' network, and may have to transfer data across long geographical distances, which in turn increases execution time and degrades the overall performance of a workflow. In this paper we present CloudForecast: a Web service framework and analysis tool which given a workflow specification, computes the optimal Amazon EC2 Cloud region to automatically deploy the orchestration engine and execute the workflow. We use geographical distance of the workflow, network latency and HTTP round-trip time between Amazon Cloud regions and the workflow nodes to find a ranking of Cloud regions. This combined set of simple metrics effectively predicts where the workflow orchestration engine should be deployed in order to reduce overall execution time. We evaluate our approach by executing randomly generated data-intensive workflows deployed on the PlanetLab platform in order to rank Amazon EC2 Cloud regions. Our experimental results show that our proposed optimisation strategy, depending on the particular workflow, can speed up execution time on average by 82.25 compared to local execution. We also show that the standard deviation of execution time is reduced by an average of almost 65 using the optimisation strategy.
The or FICAS @cite_5 is a distributed data-flow architecture for composing software services. Composition of the services in the FICAS architecture is specified using the Compositional Language for Autonomous Services (CLAS), which is essentially a sequential specification of the relationships among collaborating services. This CLAS program is then translated by the build-time environment into a control sequence that can be executed by the FICAS runtime environment.
@cite_5
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This paper presents FICAS, a distributed data-flow infrastructure for composing software services into megaservices. We discuss the basic features of FICAS that enable the distribution of data-flows within megaservices. An autonomous service access protocol, ASAP, is defined to enforce the explicit separation of control-flows from dataflows of software services. We illustrate the procedure to construct and optimize megaservice execution plans that form distributed data-flows among collaborating services. The megaservice performance under FICAS is evaluated and compared with that under the centralized data-flow infrastructures. FICAS enhances the megaservice performance and is especially suitable for large-scale service composition. We extend the service abstraction in the Open Grid Services Architecture ogsa for Quality of Service (QoS) properties. The realization of QoS often requires mechanisms such as advance or on-demand reservation of resources, varying in type and implementation, and independently controlled and monitored. propose the GARA FostKessl99 architecture. The GARA library provides a restricted representation scheme for encoding resource properties and the associated monitoring of Service Level Agreements (SLAs). Our focus is on the application layer, whereby a given service may indicate the QoS properties it can offer, or where a service may search for other services based on particular QoS properties. Service-oriented architecture (SOA) is a relatively new approach to software system development. It divides system functionality to independent, loosely coupled, interoperable services. In this paper we propose a new heterogeneous specification approach for SOA systems where a heterogeneous structured specification consists of a number of specifications of individual services written in a "local" logic and where the specification of their interactions is separately described in a "global" logic. A main feature of our global logic is the possibility of describing the dynamic change of service communications over time. Our approach is based on the theory of institutions: we show that both logics form institutions and that these institutions are connected by an institution comorphism. We illustrate our approach by a simple scenario of an e-university management system and show the power of the heterogeneous specification approach by a compositional refinement of the scenario. Service-Oriented Architecture (SOA) provides a flexible framework for service composition. Using standard-based protocols (such as SOAP and WSDL), composite services can be constructed by integrating atomic services developed independently. Algorithms are needed to select service components with various QoS levels according to some application-dependent performance requirements. We design a broker-based architecture to facilitate the selection of QoS-based services. The objective of service selection is to maximize an application-specific utility function under the end-to-end QoS constraints. The problem is modeled in two ways: the combinatorial model and the graph model. The combinatorial model defines the problem as a multidimension multichoice 0-1 knapsack problem (MMKP). The graph model defines the problem as a multiconstraint optimal path (MCOP) problem. Efficient heuristic algorithms for service processes of different composition structures are presented in this article and their performances are studied by simulations. We also compare the pros and cons between the two models.