In Perfect Harmony: Orchestrating Causality in Actor-Based Systems

2026-03-18

AI Summary

This work addresses the challenge of runtime verification in actor-based concurrent systems, where causal dependencies across actors and nondeterministic message interleavings obscure precise execution semantics—a problem exacerbated by the limited applicability of existing tools, which are largely confined to single-process settings. To overcome this, the authors propose ACTORCHESTRA, a framework that, for the first time, enables automatic instrumentation of Erlang systems compliant with the OTP standard without requiring source code modifications, thereby establishing a multi-actor causal tracing infrastructure. Complementing this, they introduce WALTZ, a declarative domain-specific language that allows specification of behavioral properties from which executable, integrated monitors are automatically generated. Empirical evaluation on three real-world systems demonstrates the approach’s effectiveness in detecting complex violations, while performance assessments confirm a practical trade-off between enhanced safety guarantees and runtime overhead.

Technology Category

• Knowledge Representation and Reasoning: Action, Change, and Causality
• Constraint Satisfaction and Optimization: Satisfiability Modulo Theories
• Multiagent Systems: Other Foundations of Multi Agent Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Security and Privacy: Large-scale security measurements

Abstract

Runtime verification has gained popularity as a lightweight approach for increasing assurance in systems under scrutiny. Performing runtime checks enables dynamic monitoring and alerts for unexpected behavior, thereby improving reliability and correctness. Actor-based systems present significant challenges for runtime verification. Properties frequently span multiple actors with complex causal dependencies, while nondeterministic message interleavings can obscure execution semantics. Moreover, most existing monitoring tools are designed for single-process behavior. This paper presents ACTORCHESTRA, a runtime verification framework for Erlang that automatically tracks causality across multi-actor interactions. The framework instruments Erlang systems that comply with OTP guidelines via targeted code injection. This method establishes the orchestration infrastructure required to track causal relationships between actors without requiring manual modifications to the target system. To ease the specification of multi-actor properties, the framework provides WALTZ, a specification language that automatically compiles properties into executable Erlang monitors that integrate with the instrumented system. Three case studies demonstrate ACTORCHESTRA's effectiveness in detecting complex behavioral violations in real-world actor systems. A performance evaluation quantifies the runtime overhead of the monitoring infrastructure and analyzes the trade-offs between added safety guarantees and execution costs.

Problem

• runtime verification
• actor-based systems
• causality
• multi-actor properties
• nondeterministic message interleavings

Innovation

• runtime verification
• causality tracking
• actor-based systems
• code instrumentation
• specification language