A stepwise approach to developing staged applications
Abstract
The staged event-driven architecture (SEDA) can be seen as a milestone as regards integration of threads and events in a single model. By decomposing applications into sets of multi-threaded stages connected by event queues, SEDA allows for the use of each concurrency model where most appropriate. Inside each SEDA stage, the number and scheduling policy of threads can be adjusted to enhance performance. SEDA lends itself to parallelization on multi-cores and is well suited for many high-volume data stream processing systems and highly concurrent event processing systems. In this paper, we propose an extension to the staged model that decouples application design from specific execution environments, encouraging a stepwise approach for designing concurrent applications, similar to Foster’s PCAM methodology. We also present Leda, a platform that implements this extended model. In Leda, stages are defined purely by their role in application logic, with no concern for locality of execution, and are bound together through asynchronous communication channels, called connectors, to form a directed graph representing the flow of events inside the application. Decisions about the configuration of the application at execution time are delayed to later phases of the implementation process. Stages in the application graph can then be grouped to form clusters, and each cluster is mapped to an exclusive OS process, running on an arbitrary host. Finally, we discuss two example applications which we developed to evaluate the Leda platform.
Keywords
Concurrency Threads Event-driven Staged eventsReferences
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