UniSage: A Unified and Post-Analysis-Aware Sampling for Microservices
Traces and logs serve as the backbone of observability in microservice architectures, yet their sheer volume imposes prohibitive storage and computational burdens. To reduce overhead, operators rely on sampling; however, current frameworks generally employ a sample-before-analysis strategy. This approach creates a fundamental trade-off: to save space, systems must discard data before knowing its diagnostic value, often losing critical context required for troubleshooting anomalies and latency spikes. In this paper, we propose UniSage, a unified sampling framework that addresses this trade-off by adopting a post-analysis-aware paradigm. Unlike prior works that focus solely on tracing, UniSageintegrates both traces and logs, leveraging a lightweight anomaly detection and root cause analysis module to scan the full data stream before sampling decisions are made. This pre-computation enables a dual-pillar strategy: an analysis-guided sampler that retains high-value data associated with detected anomalies, and an edge-case sampler that preserves rare but critical behaviors to ensure diversity. Evaluation on three datasets confirms that UniSage achieves superior data retention. At a 2.5% sampling rate, UniSage captures 71% of critical traces and 96.25% of relevant logs, substantially exceeding the best existing methods (which achieve 42.9% and 1.95%, respectively). Moreover, evaluations on a real-world dataset demonstrate UniSage's efficiency; it processes a 20-minute multi-modal data block in an average of 10 seconds, making it practical for production environments.