A real-time perspective of service composition: Key concepts and some contributions
Journal of Systems Architecture: the EUROMICRO Journal
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Service-oriented architectures (SOA) provide application systems the flexibility and cost-savings of dynamically composing workflows from reusable services. However, current SOA frameworks do not provide support for real-time workflow planning and execution. The goal of the RT-Llama SOA middleware framework is to address these new requirements. It works both at the service-level, by enhancing existing SOA middleware with service execution reservation capabilities, and at the end-to-end workflow-level, by creating a distributed component infrastructure for deadline-based workflow composition. This paper focuses on the design and implementation of the Virtual CPU (VCPU) resource scheduling scheme in RT-Llama to achieve predictable process executions. We have created a prototype implementation of RT-Llama using Sun Real-time JVM running on Solaris OS. Experiments consisting of real world service applications show that requests with end-to-end deadlines can be admitted and completed before deadlines with the VCPU scheme. We also show that service class differentiation can be achieved.