RATATOSKR: WIDE-AREA ACTUATOR RPC OVER GRIDSTAT WITH TIMEL INESS, REDUNDANCY, AND SAFETY
Erlend S. Viddal · 2007
GridStat is a QoS-managed middleware framework de-signed to replace the power grid’s aging, inflexible, and slow data communications system. GridStat is a special-ization of the publish-subscribe paradigm that takes advan-tage of the semantics of periodic status data updates to pro-vide data delivery with a per-subscriber rate, latency, and redundant paths. While GridStat is well-suited for deliv-ery of sensor data over a wide-area network, its baseline one-way mechanisms are not suitable for round-trip invo-cations such as setting an acutator or calling between con-trol centers. In this paper we present the design, implemen-tation and experimental evaluation of Ratatoskr, a tunable RPC mechanism that builds on the QoS semantics of Grid-Stat and supports three kinds of redundancy. Additionally, user-defined pre- and post-condition predicates over Grid-Stat status variables are built into the call semantics. Pre-conditions can abort an RPC call if the measured conditions dictate, while post-conditions provide additional physical assurance the call succeeded.