Snapshot-Guided Feedback Control for QoS-Aware Wide-area Computility Federation

Computility federations coordinate heterogeneous resources across independent providers while preserving administrative autonomy. This autonomy limits federation-level visibility, forcing gateways to route from coarse-grained and delayed performance summaries rather than real-time internal states. Under such weak and lagged observability, deadline-miss risk for latency-critical tasks can become structurally concentrated in a small number of domains and time windows, even when federation-wide averages remain moderate. To address this problem, we propose Per-Domain SLO Feedback (PDSF), a low-dimensional closed-loop mechanism that updates bounded routing tolls from window-level summaries and biases snapshot-driven self-routing without modifying domain-local schedulers. Theoretical analysis shows that, under a weak monotonicity assumption on routing response, PDSF exhibits boundedness, forgetting, and local stability under delayed feedback. Trace-driven experiments on a multi-domain emulator using Google cluster workloads show that, compared with deployable baselines, PDSF significantly alleviates upper-tail overload severity, reduces worst-domain risk exposure, and protects latency-critical traffic without noticeable degradation to best-effort traffic. Sensitivity analysis further shows that snapshot staleness and routing concentration jointly determine the mechanism’s operating boundary and clarifies how stale measurements and aggressive routing responses amplify risk while reducing the effectiveness of low-dimensional feedback.