MISO: A CRDT-based Middleware for Stateful Objects in the Serverless Edge-Cloud Continuum
Valentin Goronjic, Stefan Nastić · 2024
Serverless functions typically depend on external services to manage the application state, which can be difficult at the Edge due to high latency and network costs. Current solutions for stateful serverless functions at the Edge either have limited support for data locality or require mutual consensus for write operations which is hard to achieve at the Edge. This paper introduces MISO, a novel middleware for serverless computing that enables stateful serverless functions across the Edge-Cloud continuum. The middleware provides MISO Objects offering data locality. It is interoperable with existing serverless platforms and allows concurrent state modifications in a decentralized manner. The main contributions of our work include: i) A novel conceptual model to maintain application state in serverless functions called MISO Objects, ii) MISO middleware and an SDK for serverless functions, and iii) The asynchronous state replication mechanism of MISO Objects using an overlay network to optimize data transfer and resource consumption. Our evaluation demonstrated that MISO outperforms the state-of-theart by up to $243 \%$ in terms of total execution time for AllReducetype operations. Furthermore, the state replication exhibits $O(n)$ scalability regarding time, throughput, memory usage, and data volume. We further demonstrate that our work can seamlessly be integrated into an open-source serverless platform and that our SDK requires up to $150 \%$ fewer lines of code and exhibits up to $75 \%$ less cognitive complexity than the state-of-the-art.