While RPCs form the bedrock of systems stacks, we posit that IoT device collections in smart spaces like homes, warehouses, and office buildings--which are all "user-facing"--require a more expressive abstraction. Orthogonal to prior work, which improved the reliability of IoT communication, our work focuses on improving the observability and programmability of IoT actions. We present the RASC (Request-Acknowledge-Start-Complete) abstraction, which provides acknowledgments at critical points after an IoT device action is initiated. RASC is a better fit for IoT actions, which naturally vary in length spatially (across devices) and temporally (across time, for a given device). RASC also enables the design of several new features: predicting action completion times accurately, detecting failures of actions faster, allowing fine-grained dependencies in programming, and scheduling. RASC is intended to be implemented atop today's available RPC mechanisms, rather than as a replacement. We integrated RASC into a popular and open-source IoT framework called Home Assistant. Our trace-driven evaluation finds that RASC meets latency SLOs, especially for long actions that last O(mins), which are common in smart spaces. Our scheduling policies for home automations (e.g., routines) outperform state-of-the-art counterparts by 10%-55%.

翻译：尽管远程过程调用（RPC）构成了系统栈的基石，但我们认为，在家庭、仓库和办公楼等“面向用户”的智能空间中，物联网设备集群需要一种更具表达力的抽象。与以往专注于提升物联网通信可靠性的研究不同，我们的工作聚焦于改善物联网操作的可观测性与可编程性。我们提出了RASC（请求-确认-开始-完成）抽象，该抽象在物联网设备操作启动后的关键节点提供确认机制。RASC更适用于物联网操作，因为这些操作在空间上（跨设备）和时间上（对给定设备随时间变化）天然具有长度差异。RASC还支持多项新功能的设计：精确预测操作完成时间、更快检测操作故障、在编程中实现细粒度依赖关系以及调度优化。RASC旨在基于现有RPC机制实现，而非替代现有机制。我们将RASC集成至名为Home Assistant的流行开源物联网框架中。基于轨迹驱动的评估表明，RASC能够满足延迟服务等级目标，尤其对于智能空间中常见的持续O(分钟)级的长时操作。我们针对家庭自动化（如日常例程）的调度策略，其性能较现有最优方案提升10%-55%。