Organising LTL monitors over distributed systems with a global clock

Users wanting to monitor distributed systems often prefer to abstract away the architecture of the system, allowing them to directly specify correctness properties on the global system behaviour. To support this abstraction, a compilation of the properties would not only involve the typical choice of monitoring algorithm, but also the organisation of submonitors across the component network. Existing approaches, considered in the context of LTL properties over distributed systems with a global clock, include the so-called orchestration and migration approaches. In the orchestration approach, a central monitor receives the events from all subsystems. In the migration approach, LTL formulae transfer themselves across subsystems to gather local information. We propose a third way of organising submonitors: choreography — where monitors are orgnized as a tree across the distributed system, and each child feeds intermediate results to its parent. We formalise this approach, proving its correctness and worst case performance, and report on an empirical investigation comparing the three approaches on several concerns of decentralised monitoring.peer-reviewe

Organising LTL monitors over distributed systems with a global clock

Users wanting to monitor distributed systems often prefer to abstract away the architecture of the system, allowing them to directly specify correctness properties on the global system behaviour. To support this abstraction, a compilation of the properties would not only involve the typical choice of monitoring algorithm, but also the organisation of submonitors across the component network. Existing approaches, considered in the context of LTL properties over distributed systems with a global clock, include the so-called orchestration and migration approaches. In the orchestration approach, a central monitor receives the events from all subsystems. In the migration approach, LTL formulae transfer themselves across subsystems to gather local information. We propose a third way of organising submonitors: choreography — where monitors are orgnized as a tree across the distributed system, and each child feeds intermediate results to its parent. We formalise this approach, proving its correctness and worst case performance, and report on an empirical investigation comparing the three approaches on several concerns of decentralised monitoring.peer-reviewe

THEMIS: A Tool for Decentralized Monitoring Algorithms

International audienceTHEMIS is a tool to facilitate the design, development, and analysis of decentralized monitoring algorithms; developed using Java and AspectJ. It consists of a library and command-line tools. THEMIS provides an API, data structures and measures for decentralized monitoring. These building blocks can be reused or extended to modify existing algorithms, design new more intricate algorithms, and elaborate new approaches to assess existing algorithms. We illustrate the usage of THEMIS by comparing two variants of a monitoring algorithm

Who is to Blame? Runtime Verification of Distributed Objects with Active Monitors

In Proceedings VORTEX 2018, arXiv:1908.09302International audienceSince distributed software systems are ubiquitous, their correct functioning is crucially important. Static verification is possible in principle, but requires high expertise and effort which is not feasible in many eco-systems. Runtime verification can serve as a lean alternative, where monitoring mechanisms are automatically generated from property specifications, to check compliance at runtime. This paper contributes a practical solution for powerful and flexible runtime verification of distributed, object-oriented applications, via a combination of the runtime verification tool Larva and the active object framework ProActive. Even if Larva supports in itself only the generation of local, sequential monitors, we empower Larva for distributed monitoring by connecting monitors with active objects, turning them into active, communicating monitors. We discuss how this allows for a variety of monitoring architectures. Further, we show how property specifications, and thereby the generated monitors, provide a model that splits the blame between the local object and its environment. While Larva itself focuses on monitoring of control-oriented properties, we use the Larva front-end StaRVOOrS to also capture data-oriented (pre/post) properties in the distributed monitoring. We demonstrate this approach to distributed runtime verification with a case study, a distributed key/value store

Runtime Verification of Temporal Properties over Out-of-order Data Streams

We present a monitoring approach for verifying systems at runtime. Our approach targets systems whose components communicate with the monitors over unreliable channels, where messages can be delayed or lost. In contrast to prior works, whose property specification languages are limited to propositional temporal logics, our approach handles an extension of the real-time logic MTL with freeze quantifiers for reasoning about data values. We present its underlying theory based on a new three-valued semantics that is well suited to soundly and completely reason online about event streams in the presence of message delay or loss. We also evaluate our approach experimentally. Our prototype implementation processes hundreds of events per second in settings where messages are received out of order.Comment: long version of the CAV 2017 pape

Can We Monitor All Multithreaded Programs?

International audienceRuntime Verification (RV) is a lightweight formal method which consists in verifying that an execution of a program is correct wrt a specification. The specification formalizes with properties the expected correct behavior of the system. Programs are instrumented to extract necessary information from the execution and feed it to monitors tasked with checking the properties. From the perspective of a monitor, the system is a black box; the trace is the only system information provided. Parallel programs generally introduce an added level of complexity on the program execution due to concurrency. A concurrent execution of a parallel program is best represented as a partial order. A large number of RV approaches generate monitors using formalisms that rely on total order, while more recent approaches utilize formalisms that consider multiple traces. In this tutorial, we review some of the main RV approaches and tools that handle multithreaded Java programs. We discuss their assumptions, limitations, ex-pressiveness, and suitability when tackling parallel programs such as producer-consumer and readers-writers. By analyzing the interplay between specification formalisms and concurrent executions of programs, we identify four questions RV practitioners may ask themselves to classify and determine the situations in which it is sound to use the existing tools and approaches

Organising LTL Monitors over Distributed Systems with a Global Clock

International audienceUsers wanting to monitor distributed systems often prefer to abstract away the architecture of the system, allowing them to directly specify correct-ness properties on the global system behaviour. To support this abstraction, a compilation of the properties would not only involve the typical choice of monitoring algorithm, but also the organisation of submonitors across the component network. Existing approaches, considered in the context of LTL properties over distributed systems with a global clock, include the so-called orchestration and migration approaches. In the orchestration approach, a central monitor receives the events from all subsystems. In the migration approach, LTL formulae transfer themselves across subsystems to gather local information. We propose a third way of organising submonitors: choreography — where monitors are orgnized as a tree across the distributed system, and each child feeds intermediate results to its parent. We formalise this approach, proving its cor-rectness and worst case performance, and report on an empirical investigation comparing the three approaches on several concerns of decentralised monitoring