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Invited Paper

DOI: 10.4230/LIPIcs.ICALP.2018.1

Consistent Distributed Memory Services: Resilience and Efficiency (Invited Paper)

Authors: Theophanis Hadjistasi and Alexander A. Schwarzmann

Published in: LIPIcs, Volume 107, 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)

Abstract

Reading, 'Riting, and 'Rithmetic, the three R's underlying much of human intellectual activity, not surprisingly, also stand as a venerable foundation of modern computing technology. Indeed, both the Turing machine and von Neumann machine models operate by reading, writing, and computing, and all practical uniprocessor implementations are based on performing activities structured in terms of the three R's. With the advance of networking technology, communication became an additional major systemic activity. However, at a high level of abstraction, it is apparently still more natural to think in terms of reading, writing, and computing. While it is hard to imagine distributed systems - such as those implementing the World-Wide Web - without communication, we often imagine browser-based applications that operate by retrieving (i.e., reading) data, performing computation, and storing (i.e., writing) the results. In this article, we deal with the storage of shared readable and writable data in distributed systems that are subject to perturbations in the underlying distributed platforms composed of computers and networks that interconnect them. The perturbations may include permanent failures (or crashes) of individual computers, transient failures, and delays in the communication medium. The focus of this paper is on the implementations of distributed atomic memory services. Atomicity is a venerable notion of consistency, introduced in 1979 by Lamport [Lamport, 1979]. To this day atomicity remains the most natural type of consistency because it provides an illusion of equivalence with the serial object type that software designers expect. We define the overall setting, models of computation, definition of atomic consistency, and measures of efficiency. We then present algorithms for single-writer settings in the static models. Then we move to presenting algorithms for multi-writer settings. For both static settings we discuss design issues, correctness, efficiency, and trade-offs. Lastly we survey the implementation issues in dynamic settings, where the universe of participants may completely change over time. Here the expectation is that solutions are found by integrating static algorithms with a reconfiguration framework so that during periods of relative stability one benefits from the efficiency of static algorithms, and where during the more turbulent times performance degrades gracefully when reconfigurations are needed. We describe the most important approaches and provide examples.

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Theophanis Hadjistasi and Alexander A. Schwarzmann. Consistent Distributed Memory Services: Resilience and Efficiency (Invited Paper). In 45th International Colloquium on Automata, Languages, and Programming (ICALP 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 107, pp. 1:1-1:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{hadjistasi_et_al:LIPIcs.ICALP.2018.1,
  author =	{Hadjistasi, Theophanis and Schwarzmann, Alexander A.},
  title =	{{Consistent Distributed Memory Services: Resilience and Efficiency}},
  booktitle =	{45th International Colloquium on Automata, Languages, and Programming (ICALP 2018)},
  pages =	{1:1--1:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-076-7},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{107},
  editor =	{Chatzigiannakis, Ioannis and Kaklamanis, Christos and Marx, D\'{a}niel and Sannella, Donald},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2018.1},
  URN =		{urn:nbn:de:0030-drops-90050},
  doi =		{10.4230/LIPIcs.ICALP.2018.1},
  annote =	{Keywords: Atomicity, shared-memory, read/write objects, fault-tolerance, latency}
}

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DOI: 10.4230/LIPIcs.OPODIS.2016.29

Computationally Light "Multi-Speed" Atomic Memory

Authors: Antonio Fernández Anta, Theophanis Hadjistasi, and Nicolas Nicolaou

Published in: LIPIcs, Volume 70, 20th International Conference on Principles of Distributed Systems (OPODIS 2016)

Abstract

Communication demands are usually the leading factor that defines the efficiency of operations on a read/write shared memory emulation in the message-passing environment. In the quest for minimizing the communication demands, the algorithms proposed either require restrictions in the system or incur high computation demands. As a result, such solutions may be not suitable to be used in practice. In this paper we focus on the practicality of implementations of atomic read/write shared memory emulation in the message-passing environment. In particular we investigate implementations that reduce both communication and computation demands. We first examine the shortcomings of the best two (in terms of communication demands) known algorithms that implement atomic single-writer multiple-reader (SWMR) atomic memory. The algorithm ccFast proposed by A. Fernández et al., achieves optimal communication by allowing each operation to complete in one round trip, with light computation requirements. Unfortunately, it relies on strict limitations on the number of readers. On the other hand, algorithm OhSam, imposes no restrictions on the system, but provides operations that require one and a half communication rounds. In the light of these shortcomings, we present two algorithms that implement multi-speed operations with light computation, and without imposing any restriction on the system. In particular, algorithm ccHybrid adopts the fast (one-round) writes and makes clients to switch to a slow (two-round) mode whenever the system is congested. On the other hand, algorithm OhFast, pushes the responsibility of deciding for the speed switch to the servers. This allows the algorithm to utilize the fast operations, and the slow one-and-a-half-rounds operations of the algorithm presented by T. Hadjistasi et al., whenever is necessary. We prove that both new algorithms preserve atomicity. To evaluate the new algorithms we implement five different atomic memory algorithms in the NS3 simulator, and we compare their performance in terms of operation latency, and ratio of slow over fast operations performed. We test the algorithms over different: (i) topologies, and (ii) operation loads. Our results support that the newly presented algorithms increase the practicality of atomic read/write atomic shared memory implementations in the message-passing, asynchronous environment.

Cite as

Antonio Fernández Anta, Theophanis Hadjistasi, and Nicolas Nicolaou. Computationally Light "Multi-Speed" Atomic Memory. In 20th International Conference on Principles of Distributed Systems (OPODIS 2016). Leibniz International Proceedings in Informatics (LIPIcs), Volume 70, pp. 29:1-29:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2017)

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@InProceedings{fernandezanta_et_al:LIPIcs.OPODIS.2016.29,
  author =	{Fern\'{a}ndez Anta, Antonio and Hadjistasi, Theophanis and Nicolaou, Nicolas},
  title =	{{Computationally Light "Multi-Speed" Atomic Memory}},
  booktitle =	{20th International Conference on Principles of Distributed Systems (OPODIS 2016)},
  pages =	{29:1--29:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-031-6},
  ISSN =	{1868-8969},
  year =	{2017},
  volume =	{70},
  editor =	{Fatourou, Panagiota and Jim\'{e}nez, Ernesto and Pedone, Fernando},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.OPODIS.2016.29},
  URN =		{urn:nbn:de:0030-drops-70980},
  doi =		{10.4230/LIPIcs.OPODIS.2016.29},
  annote =	{Keywords: atomicity, read/write objects, shared memory, operation latency}
}

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Documents authored by Hadjistasi, Theophanis

Consistent Distributed Memory Services: Resilience and Efficiency (Invited Paper)

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Computationally Light "Multi-Speed" Atomic Memory

Abstract

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