K. Marzullo and G. Neiger. Detection of global state predicates. In Procz dings of the 5th International Workshop on Distributed Algorithms (WDAG91), pages 254--272, 1991.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....once they become true. If the desired predicate were not stable then their approach may fail to detect the predicate because may turn true only between two successive snapshots. The second approach to global predicate detection is based on the construction of the lattice of global states [7, 17, 20]. This approach, first presented by Cooper and Marzullo [7] allows the detection of definitely: and possibly: The predicate possibly: is true if is true for any global state in the lattice. The predicate definitely: is true if, for all paths from the initial global state to the final ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms, pages 254--272, 1991.

....well known observation modalities possibly This author s work was supported by the Deutsche Forschungsgemeinschaft (DFG) as part of the PhD program (Graduiertenkolleg) Intelligente Systeme fur die Informations und Automatisierungstechnik at Darmstadt University of Technology. and definitely [6, 12] in asynchronous systems where a limited number of processes are allowed to crash. It is well known that crash failures are not easy to tolerate in asynchronous systems [7] since they cannot be detected with absolute certainty [3] Mechanisms to detect these failures can at best be unreliable ....

.... Every consistent observation corresponds to a path through the lattice starting at the top element, so observations are not observer independent [13] Given some predicate and by using this lattice, it is possible to define two observer independent notions of observation in the following way [6, 12]: possibly( holds iff (if and only if) there exists a consistent observation = S 1 ; S 2 ; such that holds for some S i in . definitely( holds iff for all consistent observations = S 1 ; S 2 ; there exists a state S i where holds. 4. Predicate Detection in Faulty ....

[Article contains additional citation context not shown here]

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WDAG91), pages 254--272, 1991.

....of the lattice. In a system of N processes, the worst case number of CGSs, which can occur in computations containing little communication, is Theta(S N ) where S is the maximum number of steps taken by a single process. Any detection algorithm that enumerates all CGSs like the algorithms in [CM91, MN91, JMN95, AV94] has time complexity that is at least linear in the number of CGSs. This time complexity can be prohibitive. This motivated the development of efficient algorithms for detecting restricted classes of predicates [TG93, GW94, GW96, CG98] The algorithms of Garg and Waldecker are classic examples ....

.... are optimized state space search algorithms that try to avoid exploring multiple interleavings of independent transitions [PPH97] This approach achieves the same worst case asymptotic time complexity as the aforementioned algorithm of Garg and Waldecker for Poss Phi, assuming weak vector clocks [MN91], which are updated only by events that can change the truth value of Phi and by receive events by which a process first learns of some event that can change the truth value of Phi, are used with our algorithm. Specifically, we show that persistent set selective search [God96] can be used to ....

[Article contains additional citation context not shown here]

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer, 1991.

....number of CGSs is Theta(S N ) where S is the maximum number of steps taken by a single process. This worst case comes from the (exponential) number of CGSs of a computation in which there is little communication. Any detection algorithm that enumerates all CGSs like the algorithms in [CM91, MN91, JMN95, AV97] has time complexity that is at least linear in the number of CGSs. This time complexity can be prohibitive. This motivated the development of efficient algorithms for detecting restricted classes of predicates [TG93, GW94, GW96, CG98] The algorithms of Garg and Waldecker are classic examples ....

....contain a CGS satisfying Phi. This is easily achieved by announcing that Def Phi holds whenever the to do set becomes empty. 19 of Weak Vector Clocks. An important optimization, applicable to detecting Poss and Def , is to use weak vector clocks, as described by Marzullo and Neiger [MN91]. Standard vector clocks [Mat89] as sketched in Section 2, are updated by every event. Weak vector clocks are updated only by events that can change the truth value of Phi and by receive events by which a process first learns of some event that can change the truth value of Phi. A local state ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....number of CGSs is Theta(S N ) where S is the maximum number of steps taken by a single process. This worst case comes from the (exponential) number of CGSs of a computation in which there is little communication. Any detection algorithm that enumerates all CGSs like the algorithms in [CM91, MN91, JMN95, AV97] has time complexity that is at least linear in the number of CGSs. This time complexity can be prohibitive. This motivated the development of efficient algorithms for detecting restricted classes of predicates [TG93, GW94, GW96, CG98] The algorithms of Garg and Waldecker are classic examples ....

....the computation contain a CGS satisfying Phi. This is easily achieved by announcing that Def Phi holds whenever the to do set becomes empty. Weak Vector Clocks. An important optimization, applicable to detecting Poss and Def , is to use weak vector clocks, as described by Marzullo and Neiger [MN91]. Standard vector clocks [Mat89] as sketched in Section 2, are updated by every event. Weak vector clocks are updated only by events that change the truth value of Phi and by receive events by which a process first learns of some event that changes the truth value of Phi. A local state of ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....are meaningful in the face of uncertainty of the run actually followed by the computation. To do this, the extended predicates must apply to the entire distributed computation rather than to individual runs or global states of it. There are two choices for defining predicates over computations [6,22]: 1. Possibly( Phi) There exists a consistent observation O of the computation such that Phi holds in a global state of O. 2. Definitely( Phi) For every consistent observations O of the computation, there exists a global state of O in which Phi holds. The distributed computation of Figure 16 ....

....to p 0 when p i potentially changes Phi or when p i learns that p j has potentially changed Phi. Another technique is for p i to send an empty message to all other processes when p i potentially changes Phi. These, and other techniques for limiting the number of global states are discussed in [22]. An alternative approach is to restrict the global predicate to one that can be efficiently detected, such as the conjunction and disjunction of local predicates [10] UBLCS 93 1 15 Multiple Monitors 15 Multiple Monitors There are several good reasons for having multiple monitors observe the ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the Fifth International Workshop on Distributed Algorithms (WDAG-91), Lecture Notes on Computer Science. Springer-Verlag, Delphi, Greece, October 1991.

....discuss the second aspect. This does not mean that the first aspect is not important. On the contrary, specification and detection of breakpoints is at least as important as halting the computation and it definitely is a complex task. However, the literature already suggest several approaches. In [7, 16], algorithms are given for detecting arbitrary predicates in an event based environment. In [1, 3, 12, 15, 19] specification formalisms and detection algorithms are described based on the notion of behavioral patterns. A behavioral pattern is a specification of a set of events and the causal ....

K. Marzullo and G. Neiger. Detection of Global State Predicates. In S. Toueg, P.G. Spirakis, and L.Kirousis, editors, Distributed Algorithms, volume 579 of Lecture Notes in Computer Science, pages 254--272, Berlin, Germany, 1991. Springer Verlag. Proceedings of WDAG '91, Delphi, Greece, October 1991.

....changes the global state of the computation. This approach can detect a very broad class of behaviors. The drawback is that the cost is high since it requires building a lattice, which has a time complexity that is exponential in the number of local states in the computation. Marzullo and Neiger [39] improve the performance of this approach by limiting the number of global states. Manabe and Imase [38] present an alternative method of detecting 9 possibly g which uses two identical runs of the observed program. The relative order of events is recorded in the first run and during the ....

K. Marzullo and G. Neiger. Detection of global state predicates. In Proc. of the 5th Workshop on Distributed Algorithms, pages 254--272, Delphi, Greece, October 1991.

....arrived before checking whether the property is satisfied, can be obtained as special cases. We consider first general algorithms for PossT and Def T and then more efficient algorithms that work only for predicates of a certain form. 4. 1 General Algorithms for PossT and Def T The algorithms in [CM91, MN91] can be adapted to explore the lattice hCGS e i (c) G i by (roughly) replacing each condition of the form e e hb e 0 with e e ie 0 . Following [CM91, MN91] we give algorithms in which the monitor constructs one level of the lattice of CGSs at a time. The level of a global state g ....

....algorithms that work only for predicates of a certain form. 4.1 General Algorithms for PossT and Def T The algorithms in [CM91, MN91] can be adapted to explore the lattice hCGS e i (c) G i by (roughly) replacing each condition of the form e e hb e 0 with e e ie 0 . Following [CM91, MN91], we give algorithms in which the monitor constructs one level of the lattice of CGSs at a time. The level of a global state g is P N i=1 L(S(g(i) Level of the lattice of CGSs contains the CGSs with level . Constructing one level of the lattice at a time is unnecessary and sometimes delays ....

[Article contains additional citation context not shown here]

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th International Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....once they become true. If the desired predicate OE were not stable then their approach may fail to detect the predicate because OE may turn true only between two successive snapshots. The second approach to global predicate detection is based on the construction of the lattice of global states [7, 15, 18]. This approach, first presented by Cooper and Marzullo [7] allows the detection of definitely:OE and possibly:OE . The predicate possibly:OE is true if OE is true for any global state in the lattice. The predicate definitely:OE is true if, for all paths from the initial global state to the final ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms, pages 254--272, 1991.

....number of CGSs is Theta(S N ) where S is the maximum number of steps taken by a single process. This worst case comes from the (exponential) number of CGSs of a computation in which there is little communication. Any detection algorithm that enumerates all CGSs like the algorithms in [CM91,MN91,JMN95,AV97] has time complexity that is at least linear in the number of CGSs. This time complexity can be prohibitive, so researchers have sought faster alternatives. One approach is to restrict the problem and develop efficient algorithms for detecting only certain classes of predicates ....

....of bounds on processor speed and network latency. 2 These restricted algorithms do not apply to the examples in Section 4. 2 Scott D. Stoller and Yanhong A. Liu some aspect of the problem for example, detecting a different modality [FR97] or assuming that the system is partially synchronous [MN91,Sto97] This paper presents an efficient and general approach to detecting Poss Phi. In this approach, the set of CGSs is represented symbolically, using boolean formulas implemented as ordered binary decision diagrams (BDDs) and Poss Phi is detected by testing satisfiability of a formula. ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....can be viewed as detecting a stable property. Of course, a primary motivation for monitoring a real time system is to detect a violation as early as possible. Recent work on evaluating non stable global predicates for distributed computations also relate to our work, but to a lesser extent [6, 16]. Reference [16] looks at several techniques for limiting the exponential number of states that must be considered to evaluate a property over computations. Reference [6] considers an alternative approach by restricting the global predicate to one that can be efficiently detected, such as the ....

....as detecting a stable property. Of course, a primary motivation for monitoring a real time system is to detect a violation as early as possible. Recent work on evaluating non stable global predicates for distributed computations also relate to our work, but to a lesser extent [6, 16] Reference [16] looks at several techniques for limiting the exponential number of states that must be considered to evaluate a property over computations. Reference [6] considers an alternative approach by restricting the global predicate to one that can be efficiently detected, such as the conjunction and ....

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of 5th International Workshop on Distributed Algorithms (WDAG-91), Delphi, Greece, 1991.

....our work is to detect a violation as early as possible. Furthermore, causality between event occurrences is captured by a static constraint graph in our model. Recent work on evaluating nonstable global predicates for distributed computations also relate to our work, but to a lesser extent [7] [17]. Reference [17] looks at several techniques for limiting the exponential number of states that must be considered to evaluate a property over computations. Reference [7] considers an alternative approach by restricting the global predicate to one that can be efficiently detected, such as the ....

....detect a violation as early as possible. Furthermore, causality between event occurrences is captured by a static constraint graph in our model. Recent work on evaluating nonstable global predicates for distributed computations also relate to our work, but to a lesser extent [7] 17] Reference [17] looks at several techniques for limiting the exponential number of states that must be considered to evaluate a property over computations. Reference [7] considers an alternative approach by restricting the global predicate to one that can be efficiently detected, such as the conjunction and ....

Marzullo, K. and Neiger, G. 1991. Detection of Global State predicates, Proc. of 5th International Workshop on Distributed Algorithms (WDAG-91), Delphi, Greece, Springer-Verlag.

.... above; developing efficient algorithms for detecting global properties that depend explicitly on time; and investigating clock based detection of sequences of global states, perhaps along the lines of temporal modalities based on happened before [16, 3, 11] 2 Related Work Marzullo and Neiger [23] discuss global property detection in partially synchronous systems in which a fixed bound ffl on the error between clocks is known. In the notation of this paper, they define modalities Poss hd and Def hd , where hd Delta = db [ hb , and give detection algorithms for these ....

....those involving priority queues) that are impossible if causal ordering is also used. Third, incorporating happenedbefore would have obscured the presentation and complexity analysis of the real time based parts of the algorithms, which are the novel parts. Contributions of this paper relative to [23] include: detection algorithms based purely on real time clocks; more efficient detection algorithms; and definition of and algorithm for Inst. 23] does not consider any modality analogous to Inst. Also, 23] assumes a fixed bound on the error in clock synchronization. Our framework allows that ....

[Article contains additional citation context not shown here]

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....computation [43] the global view of the computation state must also be causally consistent in order to prevent so called phantom deadlocks and false termination states. In distributed debugging, detecting global predicates is a key issue, and the causality relation is of utmost importance [15, 27, 30, 41]. Again, the problem is to obtain a consistent view in order to correctly evaluate the global predicate. Analyzing the causal relationship between events is also helpful for the detection of race conditions and other synchronization errors one of the most difficult problems in distributed ....

....domains like, e.g. debugging, the effects of intrusion are clearly undesirable they are the price we have to pay for the efficiency of the detection algorithm. In cases, however, where the detection of global states is an integral part of the system (e.g. in distributed reactive systems [29, 41] where the system itself is essentially a monitor receiving stimuli from its environment through a network of sensors, and reacting to these stimuli through actuators) a moderate amount of intrusion may be tolerable as long as sufficient potential for concurrency is retained. Cooper s and ....

K. Marzullo and G. Neiger. "Detection of Global State Predicates". Proc. 5th Workshop on Distributed Algorithms (WDAG-91), Delphi, Greece, S.Toueg, P.G. Spirakis, L. Kirousis (eds.), Springer-Verlag, LNCS 579, pp. 254-272, Oct. 1991.

....where S is the maximum number of steps taken by a single process. 2 This worst case comes from the (exponential) number of histories consistent with a computation in which there is little communication. Any detection algorithm that constructs the entire lattice whether it uses the method in [CM91, MN91] or the more efficient schemes in [DJR93, JMN95] has worst case time complexity that is at least linear in the size of the lattice. Thus, Cooper and Marzullo s algorithms for detecting Poss Phi and Def Phi have worst case time complexity Omega Gamma S N ) Because the time needed to ....

.... Omega Gamma S N ) Because the time needed to construct the lattice can be prohibitive, researchers have sought faster detection algorithms. One approach has been to change the problem for example, detecting a different modality [FR94] or assuming that the system is partially synchronous [MN91]. Another approach has been to restrict the problem and develop efficient algorithms for detecting only certain classes of predicates [GW92, GW94, TG94] Our work is inspired by an algorithm of Garg and Waldecker for a restricted problem [GW94] Their algorithm detects Poss Phi only for Phi a ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms, volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....they are applied repeatedly [14] No matterhow frequently taken, a sequence of snapshotsmayhave gaps that correspond to exactly those global statesin which the (non stable) predicate holds. Any reasonable definition of detection for the case of non stable predicates must be based on observations [20, 5, 13, 8, 1]. A further complexity in detecting non stable predicates is due to the socalled relativistic effect which results in multiple observations for the same computation. Modal operators have been proposed so as to make detection of non stable predicates independent of any particular observation [5, ....

....8, 1] A further complexity in detecting non stable predicates is due to the socalled relativistic effect which results in multiple observations for the same computation. Modal operators have been proposed so as to make detection of non stable predicates independent of any particular observation [5, 13, 8]. While predicates (stable or not) over a single global state are able to capture many interesting system properties, they inherently lack notions of logical time or relative order. In order to characterize dynamic properties and behavioral patterns of distributed computations, simple predicate ....

[Article contains additional citation context not shown here]

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the Fifth International Workshop on Distributed Algorithms (WDAG-91), Lecture Notes on Computer Science. Springer-Verlag, Delphi, Greece, October 1991.

....computation [Mat87] the global view of the computation state must also be causally consistent in order to prevent so called phantom deadlocks and false termination states. In distributed debugging, detecting global predicates is a key issue, and the causality relation is of utmost importance [CoM91, HaW88, HsK90, MaN91]. Again, the problem is to obtain a consistent view in order to correctly evaluate the global predicate. Analyzing the causal relationship between events is also helpful for the detection of race conditions and other synchronization errors one of the most difficult problems in distributed ....

....domains like, e.g. debugging, the effects of intrusion are clearly undesirable they are the price we have to pay for the efficiency of the detection algorithm. In cases, however, where the detection of global states is an integral part of the system (e.g. in distributed reactive systems [HaP85, MaN91] where the system itself is essentially a monitor receiving stimuli from its environment through a network of sensors, and reacting to these stimuli through actuators) a moderate amount of intrusion may be tolerable as long as sufficient potential for concurrency is retained. Cooper s and Marzullo ....

K. Marzullo and G. Neiger. "Detection of Global State Predicates". Proc. 5th Workshop on Distributed Algorithms (WDAG-91), Delphi, Greece, S.Toueg, P.G. Spirakis, L. Kirousis (eds.), Springer-Verlag, LNCS 579, pp. 254-272, Oct. 1991.

....3 describes the properties our Failure Suspector components must satisfy. These are weak yet reasonable requirements, and are easily implemented in any asynchronous system. Section 4 discusses VC p , and Section 5 discusses MC p . These components execute protocols to detect global properties [8, 15]. 3 The Failure Suspector Given process p, FS p emits a sequence of not comm(q) and comm(r) suspicion messages to MC p and VC p . Since the system is asynchronous we cannot guarantee the accuracy or timeliness of these suspicions; the most we can require is that FS p eventually suspects true ....

K. Marzullo and G. Neiger. Detection of Global State Predicates. In Proceedings fo the Fifth International WDAG, pages 254--272. Springer-Verlag (LNCS 579), 1991. Delphi, Greece.

....system is characterized by lack of synchronized clocks and lack of bounds on processor speed and network latency. comes from the (exponential) number of CGSs of a computation in which there is little communication. Any detection algorithm that enumerates all CGSs whether using the method in [CM91, MN91] or one of the more efficient schemes in [JMN95, AV97] has time complexity that is at least linear in the number of CGSs. This time complexity can be prohibitive, so researchers have sought faster alternatives. One approach has been to restrict the problem and develop efficient algorithms for ....

.... been to restrict the problem and develop efficient algorithms for detecting only certain classes of predicates [GW94, TG93] 2 Another approach has been to modify some aspect of the problem for example, detecting a different modality [FR94a] or assuming that the system is partially synchronous [MN91, Sto97]. This paper presents an efficient and general approach to detecting Poss Phi. In this approach, the set of CGSs is represented symbolically, using ordered binary decision diagrams. This can be much more efficient than explicit enumeration. For simplicity, we consider here only off line ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th International Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....linear time is often inappropriate [La78, Pr86] Application problems decompose into questions about more general temporal relations; clocks for these relations would provide building blocks for application solutions. These applications include the following: ffl snapshots and global states [MaNe91, MaSa91, Ma93, Sm94] ffl deadlock detection [KsSi90, Ma87, TaLo91] ffl immediate ordered service [KeKo89] ffl optimistic rollback recovery [Jo89, JoZw90, PeKe93, SJT94, StYe85] 2.1. Partial Order Time Partial order time (POT) is the major alternative time model to global sequential time. Suppose our system ....

K. Marzullo and G. Neiger. "Detection of Global State Predicates." In Toueg, Spirakis and Kirousis (ed.), 5th International Workshop on Distributed Algorithms (WDAG-91). Springer-Verlag LNCS 579. 1991.

....number of CGSs is Theta(S N ) where S is the maximum number of steps taken by a single process. This worst case comes from the (exponential) number of CGSs of a computation in which there is little communication. Any detection algorithm that enumerates all CGSs like the algorithms in [CM91,MN91,AV97] has time complexity that is at least linear in the number of CGSs. This time complexity can be prohibitive, so researchers have sought faster alternatives. One approach is to restrict the problem and develop efficient algorithms for detecting only certain classes of predicates ....

.... approach is to restrict the problem and develop efficient algorithms for detecting only certain classes of predicates [GW94,TG93] 2 Another approach is to modify some aspect of the problem for example, detecting a different modality [FR97] or assuming that the system is partially synchronous [MN91,Sto97] This paper presents an efficient and general approach to detecting Poss Phi. In this approach, the set of CGSs is represented symbolically, using boolean formulas implemented as ordered binary decision diagrams (BDDs) and Poss Phi is detected by testing satisfiability of a formula. ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG '91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

....arrived before checking whether the property is satisfied, can be obtained as special cases. We consider first general algorithms for PossT and Def T and then more efficient algorithms that work only for predicates of a certain form. 4. 1 General Algorithms for PossT and Def T The algorithms in [CM91, MN91] can be adapted to explore lattice hCGS e i (c) G i by (roughly) replacing each condition of the form e e hb e 0 with e e ie 0 . Following [CM91, MN91] we give algorithms in which the monitor constructs one level of the lattice of CGSs at a time. The level of a global state g is ....

....efficient algorithms that work only for predicates of a certain form. 4.1 General Algorithms for PossT and Def T The algorithms in [CM91, MN91] can be adapted to explore lattice hCGS e i (c) G i by (roughly) replacing each condition of the form e e hb e 0 with e e ie 0 . Following [CM91, MN91], we give algorithms in which the monitor constructs one level of the lattice of CGSs at a time. The level of a global state g is P N i=1 L(S(g(i) Level of the lattice of CGSs contains the CGSs with level . Constructing one level of the lattice at a time is unnecessary and sometimes ....

[Article contains additional citation context not shown here]

K. Marzullo and G. Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms (WDAG '91), vol. 579 of Lecture Notes in Computer Science, pages 254--272. Springer, 1991.

No context found.

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the Fifth International Workshop on Distributed Algorithms (WDAG-91), Lecture Notes on Computer Science. Springer-Verlag, Delphi, Greece, October 1991.

....relative processor speed with respect to the communication bandwidth and the overhead (and hence the frequency) of checkpointing. Putting these results in a broader context, causal message logging protocols are related to causal multicast [25] which in turn are related to global state detection [1, 14]. All of these protocols track causal dependencies to implement some level of distributed knowledge about the execution history of some application. For example, in [4] we showed howacausal message logging protocol can be derived starting from causal multicast. And, if f = n then casual message ....

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of Fifth International Conference on Distributed Algorithms, pages 257--272, October 1991.

....that this state ever existed, then it cannot guarantee that the action ff i takes place in that state. This leaves the question of what semantics Meta should supply for reaction after detection. We have developed several different semantics and have designed protocols that support our semantics [15, 8]. The strongest condition that these protocols support is detecting OE i if and only if OE i held on a consistent cut and the system blocks long enough to guarantee that the reaction occurs in a state satisfying OE i . Weaker conditions include detecting OE i if and only if OE i held at some point ....

....that deleted a file when two users on different machines had their delete buttons simultaneously depressed. For this rule, the weakest condition would not be sufficient: the file may be deleted if the buttons were both depressed, but not at the same time. Unfortunately, all of our other protocols [15] are expensive and are not practical unless some blocking of the application is introduced. We are currently incorporating and experimenting with these protocols in order to better understand how this blocking could affect the instrumented system s performance. 5.4 Atomicity It is relatively ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In S. Toueg, P. G. Spirakis, and L. Kirousis, editors, Distributed Algorithms: Proceedings of the Fifth Workshop on Distributed Algorithms and Graphs, October 1991, volume 579 of Lecture Notes on Computer Science, pages 254--272. Springer-Verlag, 1991. 28

....message to p 0 when p i potentially changes F or when p i learns that p j has potentially changed F. Another technique is for p i to send an empty message to all other processes when p i potentially changes F. These, and other techniques for limiting the number of global states are discussed in [5]. 2.2 Detecting Currently F In contrast to the previous two algorithms, detecting Currently F is computationally cheap but may block the monitored program, as discussed in Section 1. Figures 5 and 6 give a protocol that detects Currently F for conditions that do not reference the number of ....

K. Marzullo and G. Neiger. Detection of global state predicates. In preparation.

....are meaningful in the face of uncertainty of the run actually followed by the computation. To do this, the extended predicates must apply to the entire distributed computation rather than to individual runs or global states of it. There are two choices for defining predicates over computations [6,22]: 1. Possibly(F) There exists a consistent observation O of the computation such that F holds in a global state of O. 2. Definitely(F) For every consistent observations O of the computation, there exists a global state of O in which F holds. The distributed computation of Figure 16 satisfies ....

....message to p 0 when p i potentially changes F or when p i learns that p j has potentially changed F. Another technique is for p i to send an empty message to all other processes when p i potentially changes F. These, and other techniques for limiting the number of global states are discussed in [22]. An alternative approach is to restrict the global predicate to one that can be efficiently detected, such as the conjunction and disjunction of local predicates [10] 15 Multiple Monitors There are several good reasons for having multiple monitors observe the same computation for the purposes ....

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the Fifth International Workshop on Distributed Algorithms (WDAG91) , Lecture Notes on Computer Science. Springer-Verlag, Delphi, Greece, October 1991.

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K. Marzullo and G. Neiger. Detection of global state predicates. In Procz dings of the 5th International Workshop on Distributed Algorithms (WDAG91), pages 254--272, 1991.

No context found.

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WDAG91), pages 254--272, 1991.

No context found.

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WADG'91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

No context found.

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WADG'91), volume 579 of LNCS, pages 254--272. Springer, 1991.

No context found.

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WADG'91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

No context found.

K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WADG'91), volume 579 of Lecture Notes in Computer Science, pages 254--272. Springer-Verlag, 1991.

No context found.

Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WDAG91), pages 254--272, 1991.

No context found.

K. Marzullo and G. Neiger. Detection of global state predicates. In Proc. of the Fifth Intl. Workshop on Dist. Algorithms, pages 254--272, 1991.

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K. Marzullo and G. Neiger. Detection of global state predicates. In Proceedings of the 5th International Workshop on Distributed Algorithms (WDAG-91), pages 254-272, Delphi, Greece, October 1991.

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#MN91# Keith Marzullo and Gil Neiger. Detection of global state predicates. In Proc. 5th Int'l. Workshop on Distributed Algorithms #WDAG#, volume 579 of Lecture Notes in Computer Science, pages

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