Efficient solutions to the replicated log and dictionary problems

Wuu, Gene T. J.; Bernstein, Arthur J.

doi:10.1145/12485.12491

Cited by 38 publications

(54 citation statements)

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“…The size of the logical clocks can be reduced by modifying the system model and making simplifying assumptions, such as those made previously for vector clocks [17,22]. The size of the clocks can also be reduced by making approximations to the accurate clock value, along the lines of earlier approximations [12,19,23,24] made previously for vector and matrix clocks. These options provide directions for future research.…”

Section: Discussionmentioning

confidence: 99%

“…Although the size of each clock and timestamp of dimension α is n α integers, this can be reduced by making certain assumptions on the message communication pattern, the partial order (H, ≺), logical network topology, and on the reliable and ordered message delivery, using schemes similar to those used by Singhal and Kshemkalyani [22] and by Meldal, Sankar, and Vera [17]. Certain optimizations of matrix clocks that do not compute the accurate matrix clock but some approximation of it were described by Krishnakumar and Bernstein [12], Ruget [19], Torres-Rojas and Ahamad [23], and Wuu and Bernstein [24]. Similar techniques can be used for α-dimensional clocks if accuracy can be sacrificed.…”

Section: Fig 2 the Example Execution For Clk 3 (3-dimensional Clockmentioning

confidence: 99%

“…Matrix clocks, first proposed by Wuu and Bernstein [24], contain vector clock information about other processes' views of the system execution. A matrix clock is an array of size n × n. Clk i [j, k] is i's knowledge of process j's knowledge of process k's local (scalar) clock value.…”

Section: Introductionmentioning

confidence: 99%

“…A matrix clock is an array of size n × n. Clk i [j, k] is i's knowledge of process j's knowledge of process k's local (scalar) clock value. Some example areas that use matrix clocks are designing fault-tolerant protocols and distributed database protocols [12,24], including protocols to discard obsolete information in distributed databases [20], and protocols to solve the replicated log and replicated dictionary problems [24]. Recently, matrix clocks have also been used to implement the disconnected mode of operation in mobile databases [11].…”

Section: Introductionmentioning

confidence: 99%

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The power of logical clock abstractions

Kshemkalyani

2004

Distrib. Comput.

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Vector and matrix clocks are extensively used in asynchronous distributed systems. This paper asks, "how does the clock abstraction generalize?" To address this problem, the paper motivates and proposes logical clocks of arbitrary dimensions. It then identifies and explores the conceptual link between such clocks and knowledge. It establishes the necessary and sufficient conditions on the size and dimension of clocks required to attain any specified level of knowledge about the timestamp of the most recent system state for which this is possible without using any messages in the clock protocol. The paper then gives algorithms to determine the timestamp of the latest system state about which a specified level of knowledge is attainable in a given system state, and to compute the timestamp of the earliest system state in which a specified level of knowledge about a given system state is attainable. The results are applicable to applications that deal with a certain class of properties, identified as monotonic properties.

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Section: Discussionmentioning

confidence: 99%

Section: Fig 2 the Example Execution For Clk 3 (3-dimensional Clockmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The power of logical clock abstractions

Kshemkalyani

2004

Distrib. Comput.

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“…We also discussed how the algorithm can be adapted to various special situations outside the scope of Problem 1. In the face of network failures, techniques from [25] can be adapted for log management to maintain causal consistency.…”

Section: Discussionmentioning

confidence: 99%

Necessary and sufficient conditions on information for causal message ordering and their optimal implementation

Kshemkalyani¹,

Singhal²

1998

Distributed Computing

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This paper formulates necessary and sufficient conditions on the information required for enforcing causal ordering in a distributed system with asynchronous communication. The paper then presents an algorithm for enforcing causal message ordering. The algorithm allows a process to multicast to arbitrary and dynamically changing process groups. We show that the algorithm is optimal in the space complexity of the overhead of control information in both messages and message logs. The algorithm achieves optimality by transmitting the bare minimum causal dependency information specified by the necessity conditions, and using an encoding scheme to represent and transmit this information. We show that, in general, the space complexity of causal message ordering in an asynchronous system is Ω(n 2 ), where n is the number of nodes in the system. Although the upper bound on space complexity of the overhead of control information in the algorithm is O(n 2 ), the overhead is likely to be much smaller on the average, and is always the least possible. Background and previous workA distributed system consists of a collection of geographically dispersed autonomous sites connected by a communication network. The sites do not share any memory and communicate solely by message passing. Message propagation delay is finite but unpredictable, and between a pair of sites, messages may be delivered out of order. There is no common physical clock.The execution of a process at a site is modeled by three types of events, namely, message send, message delivery 1 , The results of this paper appear in [10] and a brief announcement of the optimal implementation of the results appears in [11]. Correspondence to: A.D. Kshemkalyani 1 It is important to distinguish between the arrival of a message and its delivery. The arrival of a message signifies that the communication and internal events. An internal event represents a local computation at the process, whereas message send and delivery events establish cause and effect relationships among the processes. The cause and effect relationship between the events of a distributed execution is captured by the happened before or causality relation (−→) [14] which defines a partial order on the events.There exist several paradigms for ordered delivery of messages in a distributed system (see Fig. 1). Synchronous communication between processes, that tantamounts to instantaneous message delivery, simplifies the design, verification, and analysis of distributed applications. However, it results in a loss in concurrency within the distributed application because each message exchange requires a handshake between the sender and the receiver. FIFO and non-FIFO communication on each channel are asynchronous and provide much more concurrency to the distributed application, but the asynchronous execution of processes and unpredictable communication delays create nondeterminism in distributed systems that complicates the design, verification, and analysis of distributed applications. To simplify the design and d...

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The Lord of the Rings: Efficient Maintenance of Views at Data Warehouses

Agrawal

Abbadi

Mostéfaoui

et al. 2002

Lecture Notes in Computer Science

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Data warehouses have become extremely important to support online analytical processing (OLAP) queries in databases. Since the data view that is obtained at a data warehouse is derived from multiple data sources that are continuously updated, keeping a data warehouse up-to-date becomes a crucial problem. An approach referred to as the incremental view maintenance is widely used. Unfortunately, a precise and formal definition of view maintenance (which can actually be seen as a distributed computation problem) does not exist. This paper develops a formal model for maintaining views at data warehouses in a distributed asynchronous system. We start by formulating the view maintenance problem in terms of abstract update and data integration operations and state the notions of correctness associated with data warehouse views. We then present a basic protocol and establish its proof of correctness. Finally, we present an efficient version of the proposed protocol by incorporating several optimizations. So, this paper is mainly concerned with basic principles of distributed computing and their use to solve database related problems.

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Efficient solutions to the replicated log and dictionary problems

Cited by 38 publications

References 5 publications

The power of logical clock abstractions

The power of logical clock abstractions

Necessary and sufficient conditions on information for causal message ordering and their optimal implementation

The Lord of the Rings: Efficient Maintenance of Views at Data Warehouses

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