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[ excerpt from developer's web site with modifications ]
The goal is to build a system capable of supporting massive concurrency
(on the order of tens of thousands of simultaneous client connections)
and avoid the pitfalls which arise with traditional thread and
event-based approaches.
SEDA is an acronym for staged event-driven architecture, and
decomposes a complex, event-driven application into a set of stages
connected by queues. This design avoids the high overhead associated
with thread-based concurrency models, and decouples event and thread
scheduling from application logic. By performing admission control
on each event queue, the service can be well-conditioned to load,
preventing resources from being overcommitted when demand exceeds
service capacity. SEDA employs dynamic control to automatically
tune runtime parameters (such as the scheduling parameters of each
stage), as well as to manage load, for example, by performing
adaptive load shedding. Decomposing services into a set of stages
also enables modularity and code reuse, as well as the development
of debugging tools for complex event-driven applications.
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