The compute continuum is a model of deployment and computation that envelopes the Cloud and the Edge into a seamless runtime infrastructure. Vast heterogeneity at the Edge is one of the main challenges of the continuum. A lightweight uniform runtime, such as the one offered by WebAssembly (Wasm) may be an apt response to that. The other main challenge is the occasional need for computations to relocate. This happens when local resources are insufficient or inadequate to meet the application requirements or when location changes in the physical world require the computation to move with them. The notion of live migration applied to Wasm computations is not new. Yet, state-of-the-art solutions focus on either non-standard Wasm runtimes or interpreted modules. Supporting live migration for compiled modules across heterogeneous nodes is still an open challenge. This paper presents a mechanism to meet that need. By injecting checkpoint and restore procedures into a function bytecode within a Wasm module, we enable it to save its execution state and resume from it after a migration event. This paper presents two strategies for that, one of which with notably small run-time overhead. To assess the quality of the proposed strategies, we performed an empirical evaluation based on an open-source benchmark. The tools developed in this work are entirely open-source.

Devices at the Edge of the network are experiencing a considerable increase in computational resources. At the same time, connectivity becomes more pervasive. These phenomena jointly facilitate the emergence of a new computational model, increasingly referred to as the Continuum of Computing. This model aims at including Edge resources in Cloud-like (and Cloud-inclusive) resource pooling to accommodate computations that need reduced latency, increased privacy, and general mobility. This model has the potential to enhance the power and the reach of high-performance computing (HPC) applications, making them extend up to the Edge of the network. However, managing a pool of resources that span across both Cloud and Edge nodes poses new challenges. Moving data across the network generates latency and security issues, while national policies may outright limit data mobility. This suggests moving computation towards data instead of the usual opposite. Enabling migrating computation is one of key traits of the envisioned Continuum of Computing. The vast heterogeneity in the technological stacks and the lack of uniform standards, however, hinder the deployment of applications in the Continuum. The availability of a common runtime environment across all host nodes of the Continuum is an obvious way to circumvent those problems, reviving the write-once-run-anywhere promise in that context. The ability to move computations opportunistically after user-specific performance objectives is another key trait of the Continuum model, which also is a foundation to spatial computing, a context-aware and space-aware computing paradigm. How to effectively orchestrate migrating computations so that they can deliver value added to their users is still an open question. There is a general understanding that Cloud-native orchestrators perform poorly when shifting towards the Edge, due to exceedingly restrictive (Cloud-centric) assumptions underneath their orchestration model. The matter of efficient orchestration in the Continuum is paramount in the envisioned model. To showcase the feasibility and viability of a Continuum-worthy runtime infrastructure, we singled out two emerging technologies: Rust and WebAssembly. The Rust programming language's highlight is its statically-checked memory safety. WebAssembly's highlights are solid guarantees of isolation and a portable bytecode format for applications compiled for its Instruction Set Architecture (ISA). To this project, WebAssembly components written in Rust constitute the candidate building blocks for the Continuum infrastructure, centred on memory-safe and sand-boxed execution capsules. In addition to that, this project aims to develop and deploy Continuum-worthy orchestration capabilities that leverage seamless migration.

Hard real-time systems, characterized by stringent timeliness requirements, occur in an increasing variety of industrial sectors. Some such domains carry important safety-critical concerns, notably avionics, space, and automotive. One common design trend across those domains seeks to reduce the number of computing devices embedded in them by integrating software applications of different criticality levels into one and the same onboard computer. A safety-savvy design approach however requires isolation among components of different criticality, to prevent unintended reciprocal interference across them. Isolation is traditionally achieved through partitioning. Partitioning, however, incurs low resource utilization as cautionary margins are used to inflate partition budgets over their anticipated needs. This situation has prompted research into alternative ways to integration that can safely afford higher levels of utilization. The Mixed-Criticality (MC) approach, which concentrates on the CPU scheduling problem, has yielded a large body of research results that show considerable gains in sustained utilization, but it has yet to meet all of the isolation requirements of safety-critical systems. This work presents a solution to augment a state-of-the-art MC solution with efficient and effective spatial isolation capabilities. Experimental results show that our solution provides adequate guarantees of temporal and spatial isolation with very small runtime overhead.