Bayesian inference for queueing networks and modeling of internet services

Modern Internet services, such as those at Google, Yahoo!, and Amazon, handle billions of requests per day on clusters of thousands of computers. Because these services operate under strict performance requirements, a statistical understanding of their performance is of great practical interest. Such services are modeled by networks of queues, where each queue models one of the computers in the system. A key challenge is that the data are incomplete, because recording detailed information about every request to a heavily used system can require unacceptable overhead. In this paper we develop a Bayesian perspective on queueing models in which the arrival and departure times that are not observed are treated as latent variables. Underlying this viewpoint is the observation that a queueing model defines a deterministic transformation between the data and a set of independent variables called the service times. With this viewpoint in hand, we sample from the posterior distribution over missing data and model parameters using Markov chain Monte Carlo. We evaluate our framework on data from a benchmark Web application. We also present a simple technique for selection among nested queueing models. We are unaware of any previous work that considers inference in networks of queues in the presence of missing data.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS392 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Inference and Learning in Networks of Queues

Probabilistic models of the performance of computer systems are useful both for predicting system performance in new conditions, and for diagnosing past performance problems. The most popular performance models are networks of queues. However, no current methods exist for parameter estimation or inference in networks of queues with missing data. In this paper, we present a novel viewpoint that combines queueing networks and graphical models, allowing Markov chain Monte Carlo to be applied. We demonstrate the effectiveness of our sampler on real-world data from a benchmark Web application.

Probabilistic Inference in Queueing Networks

Although queueing models have long been used to model the performance of computer systems, they are out of favor with practitioners, because they have a reputation for requiring unrealistic distributional assumptions. In fact, these distributional assumptions are used mainly to facilitate analytic approximations such as asymptotics and large-deviations bounds. In this paper, we analyze queueing networks from the probabilistic modeling perspective, applying inference methods from graphical models that afford significantly more modeling flexibility. In particular, we present a Gibbs sampler and stochastic EM algorithm for networks of M/M/1 FIFO queues. As an application of this technique, we localize performance problems in distributed systems from incomplete system trace data. On both synthetic networks and an actual distributed Web application, the model accurately recovers the system’s service time using 1 % of the available trace data.

Lowest-Low Fertility in Japan: Consequences For A Once-Great Nation

Japan, once a great economic superpower, is currently one of a number of countries experiencing lowest-low fertility, having a total fertility rate of less than 1.5. This demographic figure exists alongside two decades of low economic growth, undermining confidence in national integrity and longevity. The association of low growth and lowest-low fertility has provoked a contest between two visions for national rejuvenation - one an old and increasingly discredited liberalism, and the second, a new demographic conservatism. Japan's debate is not new or unique. Questioning the methods for national replacement and the relationship between fertility and national integrity remains a crucial aspect of nationalism in a globalized world. In the Japanese context, the contest is between two visions for the nation - on the one hand, a cautious nationalism with attendant liberal proclivities; on the other a more conservative vision for the role of women in the family and civic duties. The election of the Democratic Party of Japan (DJP) in 2009 saw fertility issues prominent in the election campaign. Nonetheless, recapturing the lost economic greatness and the role of fertility in definitions of Japanese nationalism remain unresolved and controversial issues

A Study of the Effects of the Track Starter\u27s Time Intervals

[From the Introduction, Statement of the Problem] The purpose of this study was to investigate the effects of the track starter\u27s time interval on the performance of the track runner. It was also a purpose of the study to show the need for more competent starters and clinics for training these officials

Legislating the Tower of Babel: International Restrictions on Internet Content and the Marketplace of Ideas

The First Amendment to the U.S. Constitution protects the expression of diverse viewpoints in virtually any medium. Nevertheless, the modern novelty of borderless communication via the Internet strains our ideal of keeping government out of the business of regulating speech. This Note reveals the conflict between the First Amendment\u27s national protections and the Internet\u27s lack of national boundaries, while also arguing for international intervention for the protection of free speech. This Author articulates the real danger of watered-down speech unless both the FCC and the international community provide regulations and harmonized international standards for online content that reflect First Amendment protections

The Relationship Between Stressor Rankings And Management Styles Of Nevada Elementary And Secondary Public School Principals (Leadership Style, Stress)

The purpose of this study was to determine what relationships existed between various stressor rankings selected from the Administrative Events Stress Inventory, and selected leadership styles as determined by the Leader Adaptability Style Inventory and exhibited by the elementary and secondary school administrators in the State of Nevada; The findings of the study were: (1) A majority of Nevada school principals were of the leadership style consisting of a High Task/High Relationship orientation. (2) There were no significant correlations between the four leadership styles as determined by the Leader Adaptability Style Inventory and selected job stressor events selected from the Administrative Events Stress Inventory. (3) A negative Pearson Product-Moment Correlation Coefficient was determined to exist between leadership styles involving Low Task orientation and job stressor events. (4) A positive Pearson Product-Moment Correlation Coefficient was determined to exist between the leadership styles involving a High Task orientation and job stressor events

Undergraduate student perceptions of academic dishonesty as a function of ethnicity and religious participation

The purpose was to examine undergraduates\u27 perceptions of the nature, frequency, and possible justification of dishonest behaviors in relation to ethnicity (African-American, White American) and religious involvement (low, medium and high);Fifteen dishonest behaviors were presented. Those rated definitely cheating were: taking an exam for another student, copying from someone\u27s exam, giving or receiving signals and/or answers during an exam, using unauthorized exam notes, turning in a commercially prepared paper or one written by another student;Behaviors considered probably cheating were: bringing information to an exam on a disc, arranging seating in advance to facilitate copying, turning in another student\u27s computer program or illegally accessing a program, copying from a source without footnoting, adding unused items to a bibliography, getting answers to previously administered exams, and unauthorized collaboration on assignments;Perceptions of dishonesty did not differ by ethnicity. However, students who participated less in religious activities were less likely than more involved students to consider the following behaviors to be cheating: copying without footnoting and unauthorized collaboration;When frequency of dishonest behaviors was examined, at least 50 to 60 percent of students overall indicated that the following actions occurred a great deal or a fair amount : unauthorized collaboration, getting answers to previously administered exams, and copying without footnoting. Items categorized as infrequent were: taking an exam for another student, copying from someone\u27s exam, and giving or receiving signals and/or answers during an exam. Few differences were found when comparisons were made based upon ethnicity and religious involvement;Students overall agreed that cheating was never justified under any circumstances. African-Americans were slightly but significantly more likely to agree that cheating is sometimes justified to pass a course, to stay in school, to receive a better grade, to pass a course for graduation, to keep a scholarship, or when a friend asks for help. Finally, when compared to most other students in the study, African-Americans students who were least involved in religious activities were not as likely to agree that cheating is never justified under any circumstances. Results are discussed in terms of previous findings reported in the literature