Runtime Monitoring of Timing Constraints in Distributed Real-Time Systems

Abstract

Embedded real-time systems often operate under strict timing and dependability constraints. To ensure responsiveness, these systems must be able to provide the expected services in a timely manner even in the presence of faults. In this paper, we describe a run-time environment for monitoring of timing constraints in distributed real-time systems. In particular, we focus on the problem of detecting violations of timing assertions in an environment in which the real-time tasks run on multiple processors, and timing constraints can be either inter-processor or intra-processor constraints. Constraint violations are detected at the earliest possible time by deriving and checking intermediate constraints from the user-specified constraints. If the violations must be detected as early as possible, then the problem of minimizing the number of messages to be exchanged between the processors becomes intractable. We characterize a sub-class of timing constraints that occur commonly in distributed real-time systems and whose message requirements can be minimized. We also take into account the drift among the various processor clocks when detecting a violation of a timing assertion. Finally, we describe a prototype implementation of a distributed rim-time monitor.

Safe Runtime Verification of Real-Time Properties

“…Monitoring of real-time properties is far from new [4,11,10,16,3,21], but to our knowledge, there is no existing work which identifies classes of properties to ensure invariant behaviour of the monitors under slowing down or speeding up. Our approach differs from other approaches [19,8,7,2] in that our theory revolves around the observed behaviour rather than the semantic or syntactic definition of underlying logic, i.e.…”

“…The most common approach to monitoring real-time properties [4,11,10,16,21] is based on simple time constraints where each time constraint compares the timestamps of two event occurrences. Such a constraint can be used to represent a delay or deadline constraint where an event should occur after a particular delay or before a certain deadline.…”

Take Intelligent Risk and Optimize Decision Based on Time, Available Resources and Risk Tolerance Limits

“…In [21] and [9], the authors extend the timing constraint specification and violation detection algorithm to distributed real-time systems. They indicate that the derivation of implicit constraints is essential for catching timing violations at an earlier time since it is possible that an implicit constraint is violated before an explicit delay or deadline becomes unsatisfiable at run-time.…”

Requirements-based monitors for real-time systems

“…2) Temporal properties -the order of events, which can be checked by comparing the sequence of observed events with that specified by either a temporal logic [7], [8]; a finite state machine model [15], [6]; or a context-free grammar [2]. 3) Timing constraints -the time elapsed between events, which can be expressed using a real-time logic [23], [17]; or as extensions on a finite state machine model [25], [34]. This paper contributes to this body of work in two ways: Firstly, it considers all three of these classes of properties, which we have only seen done in one other work [18].…”