Serverless computing, or Function as a Service (FaaS), represents a research trend where applications are built and deployed as a group of stateless functions. Although initially proposed for the cloud, serverless computing has also found its place on Internet of Things (IoT) while bringing functions closer to the devices, in order to reduce latency and avoid unnecessary energy and resource consumption. It is interesting that solutions can work in an integrated manner on edge, fog, and cloud layers. Mission-critical functions can be executed on edge and fog in order to benefit from low-latency responses, while heavy functions can be executed on the cloud to process huge amount of data produced by IoT sensors, as long as Internet connection is available. Existing surveys focus on serverless computing for specific layers and do not address a broad, integrated, and systematic vision regarding how IoT benefits from serverless on edge, fog, and cloud. With this in mind, this paper provides a comprehensive Systematic Literature Review that, after the selection process, covers 60 papers on the field of serverless computing for IoT on the three layers. This gives us insights about how functions are offloaded to different devices and how they interact with each other. We bring main components employed to incubate and execute functions, as well as the main challenges and open questions for this subject. Protocols, programming languages, and storage services related to the solutions are also presented. Finally, we show a rich taxonomy summarizing all characteristics in a single figure, along with a discussion about the overall architecture of serverless applications for IoT. We conclude that serverless computing is a promising technology for IoT applications, but several improvements still need to be made to popularize this concept and make it easier to use.

无服务器计算或功能即服务 (FaaS) 代表了一种研究趋势，即应用程序作为一组无状态功能构建和部署。尽管最初是针对云提出的，但无服务器计算也在物联网 (IoT) 上找到了自己的位置，同时使功能更接近设备，以减少延迟并避免不必要的能源和资源消耗。有趣的是，解决方案可以在边缘、雾和云层上以集成方式工作。关键任务功能可以在边缘和雾上执行，以从低延迟响应中受益，而重功能可以在云端执行，以处理物联网传感器产生的大量数据，只要互联网连接可用。现有调查侧重于特定层的无服务器计算，并未涉及广泛的、关于物联网如何从边缘、雾和云上的无服务器中受益的集成和系统愿景。考虑到这一点，本文提供了全面的系统文献综述，经过筛选过程，涵盖了三层物联网无服务器计算领域的 60 篇论文。这让我们深入了解功能如何卸载到不同的设备以及它们如何相互交互。我们带来了用于孵化和执行功能的主要组件，以及该主题的主要挑战和开放性问题。还介绍了与解决方案相关的协议、编程语言和存储服务。最后，我们展示了一个丰富的分类法，在一个图中总结了所有特征，并讨论了物联网无服务器应用程序的整体架构。