58 research outputs found

    Crash recovery with partial amnesia failure model issues

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    Replicated systems are a kind of distributed systems whose main goal is to ensure that computer systems are highly available, fault tolerant and provide high performance. One of the last trends in replication techniques managed by replication protocols, make use of Group Communication Sys- tem, and more specifically of the communication primitive atomic broadcast for developing more eficient replication protocols. An important aspect in these systems consists in how they manage the disconnection of nodes {which degrades their service{ and the connec- tion/reconnection of nodes for maintaining their original support. This task is delegated in replicated systems to recovery protocols. How it works de- pends specially on the failure model adopted. A model commonly used for systems managing large state is the crash-recovery with partial amnesia be- cause it implies short recovery periods. But, assuming it implies arising several problems. Most of them have been already solved in the literature: view management, abort of local transactions started in crashed nodes { when referring to transactional environments{ or for example the reinclu- sion of new nodes to the replicated system. Anyway, there is one problem related to the assumption of this second failure model that has not been completely considered: the amnesia phenomenon. Phenomenon that can lead to inconsistencies if it is not correctly managed. This work presents this inconsistency problem due to the amnesia and formalizes it, de ning the properties that must be ful lled for avoiding it and de ning possible solutions. Besides, it also presents and formalizes an inconsistency problem {due to the amnesia{ which appears under a speci c sequence of events allowed by the majority partition progress condition that will imply to stop the system, proposing the properties for overcoming it and proposing di erent solutions. As a consequence it proposes a new majority partition progress condition. In the sequel there is deDe Juan MarĂ­n, R. (2008). Crash recovery with partial amnesia failure model issues [Tesis doctoral no publicada]. Universitat PolitĂšcnica de ValĂšncia. https://doi.org/10.4995/Thesis/10251/3302Palanci

    On synchrony in dynamic distributed systems

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    [EN] Many modern distributed services are deployed in dynamic systems. Cloud services are an example. They are expected to provide service to a potentially huge amount of users and may require a wide geographical deployment in multiple data centres. Their service processes vary in volume in accordance with workload variations, showing an adaptive behaviour in order to minimise economical costs. Dynamic distributed systems may be classifed considering two axes: (a) the number of processes that compose the system, and (b) the diameter of the networking graph that interconnects those processes. Other important features of dynamic systems can be derived from these two characteristics, e.g., their attainable synchrony. We analyse the level of synchrony that may be achieved in each dynamic system class and revise the existing techniques for transforming an initially asynchronous large dynamic system into another one with a higher synchrony level. With this, a larger set of problems may be handled in dynamic distributed systems. This facilitates the implementation and provision of additional services in those systems.Muñoz-Escoí, FD.; Juan Marín, RD. (2018). On synchrony in dynamic distributed systems. Open Computer Science. 8(1):154-164. https://doi.org/10.1515/comp-2018-0014S1541648

    CAP Theorem: Revision of its related consistency models

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    [EN] The CAP theorem states that only two of these properties can be simultaneously guaranteed in a distributed service: (i) consistency, (ii) availability, and (iii) network partition tolerance. This theorem was stated and proved assuming that "consistency" refers to atomic consistency. However, multiple consistency models exist and atomic consistency is located at the strongest edge of that spectrum. Many distributed services deployed in cloud platforms should be highly available and scalable. Network partitions may arise in those deployments and should be tolerated. One way of dealing with CAP constraints consists in relaxing consistency. Therefore, it is interesting to explore the set of consistency models not supported in an available and partition-tolerant service (CAP-constrained models). Other weaker consistency models could be maintained when scalable services are deployed in partitionable systems (CAP-free models). Three contributions arise: (1) multiple other CAP-constrained models are identified, (2) a borderline between CAP-constrained and CAP-free models is set, and (3) a hierarchy of consistency models depending on their strength and convergence is built.Muñoz-EscoĂ­, FD.; Juan MarĂ­n, RD.; GarcĂ­a Escriva, JR.; GonzĂĄlez De MendĂ­vil Moreno, JR.; Bernabeu AubĂĄn, JM. (2019). CAP Theorem: Revision of its related consistency models. The Computer Journal. 62(6):943-960. https://doi.org/10.1093/comjnl/bxy142S943960626Davidson, S. B., Garcia-Molina, H., & Skeen, D. (1985). Consistency in a partitioned network: a survey. ACM Computing Surveys, 17(3), 341-370. doi:10.1145/5505.5508Gilbert, S., & Lynch, N. (2002). Brewer’s conjecture and the feasibility of consistent, available, partition-tolerant web services. ACM SIGACT News, 33(2), 51-59. doi:10.1145/564585.564601Muñoz-EscoĂ­, F. D., & BernabĂ©u-AubĂĄn, J. M. (2016). A survey on elasticity management in PaaS systems. Computing, 99(7), 617-656. doi:10.1007/s00607-016-0507-8Brewer, E. (2012). CAP twelve years later: How the «rules» have changed. Computer, 45(2), 23-29. doi:10.1109/mc.2012.37Attiya, H., Ellen, F., & Morrison, A. (2017). Limitations of Highly-Available Eventually-Consistent Data Stores. IEEE Transactions on Parallel and Distributed Systems, 28(1), 141-155. doi:10.1109/tpds.2016.2556669Viotti, P., & Vukolić, M. (2016). Consistency in Non-Transactional Distributed Storage Systems. ACM Computing Surveys, 49(1), 1-34. doi:10.1145/2926965Burckhardt, S. (2014). Principles of Eventual Consistency. Foundations and TrendsÂź in Programming Languages, 1(1-2), 1-150. doi:10.1561/2500000011Herlihy, M. P., & Wing, J. M. (1990). Linearizability: a correctness condition for concurrent objects. ACM Transactions on Programming Languages and Systems, 12(3), 463-492. doi:10.1145/78969.78972Lamport. (1979). How to Make a Multiprocessor Computer That Correctly Executes Multiprocess Programs. IEEE Transactions on Computers, C-28(9), 690-691. doi:10.1109/tc.1979.1675439Ladin, R., Liskov, B., Shrira, L., & Ghemawat, S. (1992). Providing high availability using lazy replication. ACM Transactions on Computer Systems, 10(4), 360-391. doi:10.1145/138873.138877Yu, H., & Vahdat, A. (2002). Design and evaluation of a conit-based continuous consistency model for replicated services. ACM Transactions on Computer Systems, 20(3), 239-282. doi:10.1145/566340.566342Curino, C., Jones, E., Zhang, Y., & Madden, S. (2010). Schism. Proceedings of the VLDB Endowment, 3(1-2), 48-57. doi:10.14778/1920841.1920853Das, S., Agrawal, D., & El Abbadi, A. (2013). ElasTraS. ACM Transactions on Database Systems, 38(1), 1-45. doi:10.1145/2445583.2445588Chen, Z., Yang, S., Tan, S., He, L., Yin, H., & Zhang, G. (2014). A new fragment re-allocation strategy for NoSQL database systems. Frontiers of Computer Science, 9(1), 111-127. doi:10.1007/s11704-014-3480-4Kamal, J., Murshed, M., & Buyya, R. (2016). Workload-aware incremental repartitioning of shared-nothing distributed databases for scalable OLTP applications. Future Generation Computer Systems, 56, 421-435. doi:10.1016/j.future.2015.09.024Elghamrawy, S. M., & Hassanien, A. E. (2017). A partitioning framework for Cassandra NoSQL database using Rendezvous hashing. The Journal of Supercomputing, 73(10), 4444-4465. doi:10.1007/s11227-017-2027-5Muñoz-EscoĂ­, F. D., GarcĂ­a-EscrivĂĄ, J.-R., Sendra-Roig, J. S., BernabĂ©u-AubĂĄn, J. M., & GonzĂĄlez de MendĂ­vil, J. R. (2018). Eventual Consistency: Origin and Support. Computing and Informatics, 37(5), 1037-1072. doi:10.4149/cai_2018_5_1037Fischer, M. J., Lynch, N. A., & Paterson, M. S. (1985). Impossibility of distributed consensus with one faulty process. Journal of the ACM, 32(2), 374-382. doi:10.1145/3149.21412

    Research network on interoperability of applications and software for networked enterprises in the Valencian Region (INTERVAL)

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    Enterprise interoperability is a tool for enhancing the competitiveness of firms, and its importance is brought out by the fact one of the EC’s strategic aims is to accomplish interoperability among European firms by the year 2010. Nevertheless, in the particular case of the Valencian Region (Spain), research into enterprise interoperability is still badly structured, fragmented, overlapping and, in many cases, practically non-existent. The INTERVAL project has been set up in an attempt to solve this problem. The scheme plans to carry out a series of initiatives aimed at integrating research activities and applying them to the complicated Valencian business sector. By so doing these companies would benefit from the application of knowledge created specifically for them and adapted to fit their characteristics. In this paper we present the details of the project, including its goals, aims, activities, results achieved, the methodology used to accomplish them, the economic and/or technological advantages, as well as possible applications and future lines of research

    Factors Associated with Postpartum Sexual Dysfunction in Spanish Women: A Cross-Sectional Study

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    (1) Background: Female sexual dysfunction (FSD) has a high prevalence globally, and perinatal factors favor FSD, especially in the postpartum period. The aim was to determine the prevalence and factors influencing FSD in the postpartum period; (2) Methods: An observational study carried out in three primary care centers in southern Spain, with women in the postpartum period who had a single low-risk birth. One hundred and seventeen women answered the Female Sexual Function questionnaire during the 4th month postpartum, between January 2020 and December 2021. Sociodemographic, obstetric, neonatal variables and level of self-esteem were analyzed. A multiple logistic regression model was carried out; (3) Results: 78.4% had high level of self-esteem. FSD prevalence was 89.7%. Factors related to FSD were having an instrumental vaginal delivery, women with university studies, and prenatal preparation. Maternal age ≄ 35, multiparity, pathological processes in the child, a medium–low level of self-esteem and newborn weight were associated with disorders in some of domains of sexual function; (4) Conclusions: FSD is highly prevalent in the postpartum period and is associated with preventable factors. A preventive approach by health professionals to these factors is essential. Health services should implement postpartum follow-up programs, which may coincide in time and place with newborn follow-up programs

    Scalability approaches for causal multicast: a survey

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    The final publication is available at Springer via http://dx.doi.org/10.1007/s00607-015-0479-0Many distributed services need to be scalable: internet search, electronic commerce, e-government... In order to achieve scalability, high availability and fault tolerance, such applications rely on replicated components. Because of the dynamics of growth and volatility of customer markets, applications need to be hosted by adaptive, highly scalable systems. In particular, the scalability of the reliable multicast mechanisms used for supporting the consistency of replicas is of crucial importance. Reliable multicast might propagate updates in a pre-determined order (e.g., FIFO, total or causal). Since total order needs more communication rounds than causal order, the latter appears to be the preferable candidate for achieving multicast scalability, although the consistency guarantees based on causal order are weaker than those of total order. This paper provides a historical survey of different scalability approaches for reliable causal multicast protocols.This work was supported by European Regional Development Fund (FEDER) and Ministerio de Economia y Competitividad (MINECO) under research Grant TIN2012-37719-C03-01.Juan MarĂ­n, RD.; Decker, H.; ArmendĂĄriz ĂĂ±igo, JE.; Bernabeu AubĂĄn, JM.; Muñoz EscoĂ­, FD. (2016). Scalability approaches for causal multicast: a survey. Computing. 98(9):923-947. https://doi.org/10.1007/s00607-015-0479-0S923947989Adly N, Nagi M (1995) Maintaining causal order in large scale distributed systems using a logical hierarchy. In: IASTED Intnl Conf on Appl Inform, pp 214–219Aguilera MK, Chen W, Toueg S (1997) Heartbeat: a timeout-free failure detector for quiescent reliable communication. In: 11th Intnl Wshop on Distrib Alg (WDAG), SaarbrĂŒcken, pp 126–140Almeida JB, Almeida PS, Baquero C (2004) Bounded version vectors. 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    Role of age and comorbidities in mortality of patients with infective endocarditis

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    [Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≄ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≄ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≄80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≄80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≄80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≄80 years; p = 0.003).Independent predictors of mortality were age ≄ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≄ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≄ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

    Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

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    The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

    Regulatory sites for splicing in human basal ganglia are enriched for disease-relevant information

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    Genome-wide association studies have generated an increasing number of common genetic variants associated with neurological and psychiatric disease risk. An improved understanding of the genetic control of gene expression in human brain is vital considering this is the likely modus operandum for many causal variants. However, human brain sampling complexities limit the explanatory power of brain-related expression quantitative trait loci (eQTL) and allele-specific expression (ASE) signals. We address this, using paired genomic and transcriptomic data from putamen and substantia nigra from 117 human brains, interrogating regulation at different RNA processing stages and uncovering novel transcripts. We identify disease-relevant regulatory loci, find that splicing eQTLs are enriched for regulatory information of neuron-specific genes, that ASEs provide cell-specific regulatory information with evidence for cellular specificity, and that incomplete annotation of the brain transcriptome limits interpretation of risk loci for neuropsychiatric disease. This resource of regulatory data is accessible through our web server, http://braineacv2.inf.um.es/
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