A Programmable and Reliable Publish/Subscribe System for Multi-Tier IoT

We introduce Canal, a programmable, topic-based, publish/subscribe system that is designed for multi-tier cloud deployments (e.g. edge-cloud, multi-cloud, IoT-cloud, etc.). Canal implements a triggered computational (i.e. “serverless”) programming model and provides developers with a uniform and portable programming interface. To achieve scalability and reliability, Canal combines the use of a distributed hash table (DHT) and replica consensus protocol to distribute and replicate functions, state, and data. Canal also decouples replica placement from the DHT topology to allow developers to optimize function placement for different objectives. We evaluate Canal using a real-world multi-tier IoT deployment and we use Canal to compare placement strategies, end-to-end performance, and failure recovery using both benchmarks and a real-world IoT-edge application. Our results show that Canal is able to achieve both low latency and reliability in this setting.