Apache HTTP Server Research Articles

Mod_bio: Apache modules for Next-Generation sequencing data.

We describe mod_bio, a set of modules for the Apache HTTP server that allows the users to access and query fastq, tabix, fasta and bam files through a Web browser. Those data are made available in plain text, HTML, XML, JSON and JSON-P. A javascript-based genome browser using the JSON-P communication technique is provided as an example of cross-domain Web service. https://github.com/lindenb/mod_bio.

Ensuring the Performance of Apache HTTP Server Affected by Aging

Failures due to software aging are typically caused by resource exhaustion, which is often preceded by progressive software performance degradation. Response time as a customer-affecting metric can thus be used to detect the onset of software aging. In this paper, we propose the distribution-based rejuvenation algorithm (DBRA), which uses a validated $({\rm M/E}_2/1/{\rm K})$ queuing model of the Apache HTTP server to decide when to trigger rejuvenation. We compare the performance of the DBRA with the one of the static rejuvenation algorithm with averaging (SRAA) presented by Avritzer et al. Simulation results show the effectiveness of the DBRA and its advantages over the SRAA in reducing the average response time. However, the DBRA generally tends to trigger rejuvenation more frequently than the SRAA, which increases the request blocking probability.

A Mobile-Based E-Learning System

E-learning is an innovative approach for delivering electronically mediated, well-designed, learner-centred interactive learning environments by utilizing internet and digital technologies with respect to instructional design principles. This paper presents the application of Software Development techniques in the development of a Mobile Based E-learning system that facilitates learning in a University environment. The developed application presents a system where a student after registration, has access to various functions that can improve the process of learning. Web pages were developed to serve as the user interface to the MLS and provide all the services needed for an E-learning portal including assessment and provision of feedback to learners. A portal exists for lecturers to upload learning contents and students’ examination results. The online portal uses Apache HTTP server as its web server, MySQL for relational database management and PHP as the scripting language to serve as a communication gateway between the back end and the users. The system was tested and evaluated with satisfactory results. This work, if adopted in schools to aid conventional learning, is expected to immensely improve the learning process and performance of students.

CONCURRIT

We present CONCURRIT, a domain-specific language (DSL) for reproducing concurrency bugs. Given some partial information about the nature of a bug in an application, a programmer can write a CONCURRIT script to formally and concisely specify a set of thread schedules to explore in order to find a schedule exhibiting the bug. Further, the programmer can specify how these thread schedules should be searched to find a schedule that reproduces the bug. We implemented CONCURRIT as an embedded DSL in C++, which uses manual or automatic source instrumentation to partially control the scheduling of the software under test. Using CONCURRIT, we were able to write concise tests to reproduce concurrency bugs in a variety of benchmarks, including the Mozilla's SpiderMonkey JavaScript engine, Memcached, Apache's HTTP server, and MySQL.

Reliability Analysis Considering the Component Collision Behavior for a Large‐scale Open Source Solution

Open source software systems that serve as key components of critical infrastructures in the society are still ever‐expanding now. Many open source software systems are developed in all parts of the world, that is, Firefox, Apache HTTP server, Linux, Android, and so on. Especially, a large‐scale open source solution composed of several open source software is now attracting attention as a next‐generation software development paradigm because of the cost reduction, quick delivery, and work saving. In this paper, we propose a new approach to software reliability assessment based on stochastic differential equations and a hierarchical Bayesian model in order to consider the interesting aspect of the collision status in the binding phase of open source software. Also, we analyze actual software fault‐count data to show numerical examples of software reliability assessment considering the component collision for several open source software. Moreover, we show that the proposed reliability analysis can assist improvement of quality for the large‐scale open source solution. Copyright © 2013 John Wiley & Sons, Ltd.

Reliability modeling and analysis for open source cloud computing

At present, cloud computing is attracting attention as a network service to share the computing resources, such as networks, servers, storage, applications, and services. Also, many open source softwares are developed in all parts of the world, e.g. Firefox, Apache HTTP server, Linux, Android, etc. This article focuses on a cloud computing environment by using open source software such as OpenStack and Eucalyptus because of the unify management of data and low cost. This article proposes a new approach to software reliability assessment based on the stochastic differential equations and hierarchical Bayesian modeling in order to consider the interesting aspect of the network status of a cloud computing environment. Also, actual software fault-count data to show numerical examples of software reliability assessment considering the characteristics of network environment is analyzed.

Web Participative Knowledge Based Crediting System

Motivated by the desire for instantaneous, accurate and relevant academic records of transferee students, the researcher explored solutions using three concepts: user web participation; knowledge-based resource; and, evaluation and crediting of expert system. All were made possible through the combination of the instructions of PHP: Hypertext Processor, Apache HTTP server, and Microsoft SQL Server 2008 R2. The credit engine as the prime mover of the system note rules and frames on crediting as its major standpoint: curriculum year, subject, unit requirement, and passing grade. Subject content is visited in cases where related but not perfectly matched subject is encountered. Discrimination is applied using words identification in three algorithms--tokenize module, SQL Like operator, and Levenshtein distance. Analysis for merging and storage uses three knowledge resources each with corresponding function: KR1 for cached invalid words; KR2 for permanent invalid words; and, KR3 for permanent valid words. The evaluators noted the utilization value of the system during the try-out with suggestions to improve on the integration of the human computer interaction (HCI); hence, a more friendly interaction is recommended.

Dynamic Software Updating Using a Relaxed Consistency Model

Software is inevitably subject to changes. There are patches and upgrades that close vulnerabilities, fix bugs, and evolve software with new features. Unfortunately, most traditional dynamic software updating approaches suffer some level of limitations; few of them can update multithreaded applications when involving data structure changes, while some of them lose binary compatibility or incur nonnegligible performance overhead. This paper presents POLUS, a software maintenance tool capable of iteratively evolving running unmodified multithreaded software into newer versions, yet with very low performance overhead. The main idea in POLUS is a relaxed consistency model that permits the concurrent activity of the old and new code. POLUS borrows the idea of cache-coherence protocol in computer architecture and uses a ”bidirectional write-through” synchronization protocol to ensure system consistency. To demonstrate the applicability of POLUS, we report our experience in using POLUS to dynamically update three prevalent server applications: vsftpd, sshd, and Apache HTTP server. Performance measurements show that POLUS incurs negligible runtime overhead on the three applications-a less than 1 percent performance degradation (but 5 percent for one case). The time to apply an update is also minimal.

Leadership and Success Factors in Online Creative Collaboration

Social computing systems have enabled new and wildly successful forms of creative collaboration to take place. Two of the best-known examples are Wikipedia and the open-source software (OSS) movement. Wikipedia, the free online encyclopedia, boasts millions of articles (over 3-6 million just in English) written by thousands of volunteers col laborating via the Internet. The OSS movement, also fueled mainly by volun teer online collaboration, has produced some of the world's most powerful and important software applications, includ ing the Apache HTTP Server, the Linux operating system, and the Mozilla Firefox Web browser. Many Wikipedia articles and OSS projects have been demon strated to be equal or superior in quality to their commercial competitors. But how is this possible? Why do online col laborations like these succeed, and what lessons can we learn from them?

Discovering programming rules and violations by mining interprocedural dependences

SUMMARYThis paper presents a novel approach to discovering implicit programming rules and rule violations in a code base, which integrates static interprocedural analysis and graph mining techniques to identify both function‐call ordering rules and conditional rules that check input parameters or return values of functions. The approach discovers rules even when rule instances cross function boundaries. Rules are modeled as graph minors of dependence graphs augmented with edges indicating shared data dependences. The approach employs two innovative algorithms: a greedy one for mining maximal frequent minors from a set of interprocedural dependence spheres and a heuristic minor‐matching algorithm for discovering rule violations. We evaluated our approach on the latest versions of three applications: net‐snmp, openssl, and the Apache HTTP server. It detected 62 new bugs (24 involving rules with interprocedural instances), 35 of which have been confirmed and fixed recently by developers based on our reports. Copyright © 2011 John Wiley & Sons, Ltd.

Cultivation of GMO in Germany: support of monitoring and coexistence issues by WebGIS technology

BackgroundIn Germany, apart from the Amflora potato licensed for cultivation since March 2010, Bt-maize MON810 is the only genetically modified organisms (GMO) licensed for commercial cultivation (about 3,000 ha in 2008). Concerns have been raised about potential adverse environmental impacts of the GMO and about potential implications on the coexistence between conventional and genetically modified production. These issues should be considered on a regional base. The objective of this article is to describe how GMO monitoring that is required after risk assessment and GMO release can be complemented by a Web-based geoinformation system (WebGIS). Secondly, it is also described how WebGIS techniques might support coexistence issues with regard to Bt-maize cultivation and conservation areas. Accordingly, on the one hand, the WebGIS should enable access to relevant geodata describing the receiving environment, including information on cultivation patterns and conservation areas containing protected species and habitats. On the other hand, metadata on already established environmental monitoring networks should be provided as well as measurement data of the intended GMO monitoring. Based on this information and based on the functionality provided by the WebGIS, the application helps in detecting possible environmental GMO impacts and in avoiding or identifying coexistence problems.ResultsThe WebGIS applies Web mapping techniques to generate maps via internet requests and offers additional functionality for analysis, processing and publication of selected geodata. It is based on open source software solely. The developments rely on a combination of the University of Minnesota (UMN ) MapServer with the Apache HTTP server, the open source database management systems MySQL and PostgreSQL and the graphical user interface provided by Mapbender. Important information on the number and the location of Bt-maize fields were derived from the GMO location register of BVL. The "WebGIS GMO Monitoring" provides different tools allowing for the application of basic GIS techniques as, for instance, automatic or interactive zooming, distance measurements or querying attribute information from selected GIS layers. More sophisticated GIS tools were implemented additionally, e.g. a buffer function which enables generating buffers around selected geo-objects like Bt-maize fields. Finally, a function for intersection of different maps was developed. The WebGIS comprises information on the location of all Bt-maize fields in Germany according to the official GMO location register of the Federal Office of Consumer Protection and Food Safety between 2005 and 2008. It facilitates, amongst others, access to geodata of GMO fields and their surroundings and can relate them with additional environmental data on climate, soil, and agricultural patterns. Furthermore, spatial data on the location of flora-fauna-habitats and environmental monitoring sites in the federal state of Brandenburg were integrated.The WebGIS GMO monitoring was implemented according to the concept for an "Information System for Monitoring GMO" (ISMO) which was designed on behalf of the German Federal Agency for Nature Conservation. ISMO includes hypotheses-based ecological effects of GMO cultivation and suggests checkpoints for GMO monitoring to test whether impacts may be observed in the receiving environment.In contrast to the public GMO register, the WebGIS GMO monitoring enables mapping of GMO fields and provides relevant geodata describing environmental and agricultural conditions in their neighbourhood of the cultivation sites as well as information derived from monitoring sites. On this basis, spatial analyses should be enabled and supported, respectively. Further, the WebGIS GMO monitoring supplements PortalU which, in Germany, is the technical realisation of the Infrastructure for Spatial Information in Europe directive (Directive 2007/2/EC) released by the EU in 2007.ConclusionsThe article should have shown how to support and complement GMO monitoring with the help of the WebGIS application. It facilitates co-operation and data access across spatial scales for different users since it is based on internet technologies. The WebGIS improves storage, analysis, management and presentation of spatial data. Apart from the improved flow of information, it supports future long-term GMO monitoring and modelling of the dispersal of transgenic pollen, for instance. Additional information (e.g. data on wind conditions or soil observation sites) provided by the WebGIS will be helpful to determine representative monitoring sites for detecting potential GMO impacts by means of monitoring or modelling. Thus, the WebGIS can also serve as part of an early warning system. In the near future, the integration of locations of all Bt-maize fields in Germany into the WebGIS as a continuous task should be automatised. Additionally, a methodology should be developed to detect maize fields by means of remote sensing data to manage coexistence problems on the basis of actual field patterns.

Divulgação de dados ambientais e socioeconômicos na internet usando um modelo baseado no uso de ferramentas livres

Um modelo baseado no uso de ferramentas livres e apresentado, visando a publicacao de dados socioeconomicos e ambientais e divulgacao de informacoes na internet. A estrutura deste modelo permite que as informacoes sejam apresentadas sob a forma de tabelas, graficos, fotos ou mapas para a web. A escolha de um determinado formato de apresentacao da informacao e determinada de acordo com os objetivos do desenvolvedor. Como resultado do trabalho, o usuario criara um banco de dados geograficos virtual para gerar informacoes estaticas e mapas interativos para a web. As principais ferramentas utilizadas foram o sistema de informacoes geograficas Spring, banco de dados relacional MySQL, PHP script e o servidor Apache HTTP.Palavras-chave: mapeamento via Web, ferramentas livres, Spring Web, Sistema de Informacao Geografica.

Component-Oriented Reliability Analysis Based on Hierarchical Bayesian Model for an Open Source Software

The successful experience of adopting distributed development models in such open source projects includes GNU/Linux operating system, Apache HTTP server, Android, BusyBox, and so on. The open source project contains special features so-called software composition by which several geographically-dispersed compo-nents are developed in all parts of the world. We propose a method of component-oriented reliability as-sessment based on hierarchical Bayesian model and Markov chain Monte Carlo methods. Especially, we fo-cus on the fault-detection rate for each component reported to the bug tracking system. We can assess the reliability for the whole open source software system by using the confidence interval for each component. Also, we analyze actual software fault-count data to show numerical examples of reliability assessment for OSS.

Performance evaluation of reliability assessment method based on stochastic differential equation model for a large-scale open source solution

At present, many open source softwares are developed in all parts of the world, i.e, Firefox, Apache HTTP server, Linux, Android, etc. Network technologies have made rapid progress with the dissemination of computer systems in all areas. These network technologies become increasingly more complex in a wide sphere. Especially, open source software systems which serve as key components of critical infrastructures in the society are still ever-expanding now. At present, a large scale open source solution by using several open source softwares is now attracting attention as the next-generation software development paradigm. In this paper, we propose a new approach to software reliability assessment by using the stochastic differential equations. Also, we analyze actual software fault-count data to show numerical examples of software reliability assessment considering component collision for several open source softwares. Especially, we show several results of performance evaluation for sensitivity analysis in terms of our model parameters. Moreover, we compare our model with the conventional model based on stochastic differential equations in terms of goodness-of-fit for actual data. We show that the proposed model can assist improvement of quality for the large scale open source solution.

A Comparative Analysis of Open Source Software Reliability

The purpose of this study is to compare the fitting (goodness-of-fit) and prediction capabilities of three reliability models using the failure data of five popular open source software (OSS) products. The failure data are modeled by Weibull and two other Non Homogenous Poisson Process (NHPP) models (Yamada S-Shaped and Schneidewind ). The OSS products considered are Eclipse , Apache HTTP Server 2 , Firefox , MPlayer OS X , and ClamWin Free Antivirus . Weibull is chosen due to its popularity in lifetime and its flexibility in modeling various distributions. On the other hand, among many software reliability models, the NHPP models are prevalent. The goodness-of-fit is based on the entire failure data collected. Prediction is accomplished by estimating the models parameters based on partial failure history and then applying the estimates to the entire time span for which failure data is collected. The outcomes show that a reliability model that fits the failure data well may not necessarily be a decent forecaster of future failure patterns.

APPLYING ASSOCIATION MINING TO CHANGE PROPAGATION

A software system evolves as changes are made to accommodate new features and repair defects. Software components are frequently interdependent, so changes made to one component can result in changes having to be made to other components to ensure that the system remains consistent; this is called change propagation. Accurate detection of change propagation is essential for software maintenance, which can be aided by accurate prediction of change propagation. In this paper, we study change propagation in three leading open-source software products: Linux, FreeBSD, and Apache HTTP Server. We use association rules-based data-mining techniques to detect change-propagation rules from the product version history. These rules are evaluated with respect to different training data sets and different test data sets. We discuss the applicability of using association-rule mining for change propagation, and several related issues. We find that a challenging issue in association-rule mining, concept drift, exists in software systems. Concept drift complicates the task of change-propagation prediction and requires special approaches, different from currently-used techniques for predicting change propagation.

The Stanford Tissue Microarray Database

The Stanford Tissue Microarray Database (TMAD; http://tma.stanford.edu) is a public resource for disseminating annotated tissue images and associated expression data. Stanford University pathologists, researchers and their collaborators worldwide use TMAD for designing, viewing, scoring and analyzing their tissue microarrays. The use of tissue microarrays allows hundreds of human tissue cores to be simultaneously probed by antibodies to detect protein abundance (Immunohistochemistry; IHC), or by labeled nucleic acids (in situ hybridization; ISH) to detect transcript abundance. TMAD archives multi-wavelength fluorescence and bright-field images of tissue microarrays for scoring and analysis. As of July 2007, TMAD contained 205 161 images archiving 349 distinct probes on 1488 tissue microarray slides. Of these, 31 306 images for 68 probes on 125 slides have been released to the public. To date, 12 publications have been based on these raw public data. TMAD incorporates the NCI Thesaurus ontology for searching tissues in the cancer domain. Image processing researchers can extract images and scores for training and testing classification algorithms. The production server uses the Apache HTTP Server, Oracle Database and Perl application code. Source code is available to interested researchers under a no-cost license.

Monitoring the “health” status of open source web‐engineering projects

PurposeIn response to the increasing number of open‐source software (OSS) project initiatives and the increasing demand of OSS products as alternative solutions by industries, it is important for particular stakeholders such as the project host/supporter project‐leading teams, and prospective customers to determine whether a project initiative is likely to be sustainable and is worth supporting. This paper aims to propose a concept of “health” indicators and an evaluation process that can help to get a status overview of OSS projects in a timely fashion and predict project survivability based on the project data available on web repositories.Design/methodology/approachFor initial empirical evaluation of the concept, the indicators are applied to well‐known web‐based OSS projects (Apache Tomcat and Apache HTTP Server) and the results are compared with challenged projects (Apache Xindice and Apache Slide). The results are discussed with OSS experts to investigate the external validity of the indicators.FindingsFrom a software project management point of view, a typical web‐based OSS project can be viewed as a web‐engineering process, since most OSS projects exploit the benefits of a web platform and enable the project community to collaborate using web‐based project tools and repositories such as mailing lists, bug trackers, and versioning systems (CVS/SVN) to deliver web systems and applications. These repositories can provide rich collections of process data, and artifacts which can be analyzed to better understand the project status.Originality/valueThe paper provides information of value about open‐source solutions.

Modeling and simulation of open source development using an agile practice

The goal of this work is to study the effects of the adoption of agile practices on open source development. In particular, we started to evaluate the effects of TDD (Test Driven Development) since it is easer to apply in a distributed environment than most other agile practices. In order to reach this goal we used the simulation modeling approach. We developed a simulation model of open source software development process. The model was tuned using data from a real FLOSS project: Apache HTTP Server. To introduce the TDD practice in our FLOSS simulation model, we made some assumptions based on empirical results. The two FLOSS development models (nonTDD and TDD) were compared. The one incorporating the agile practice yields better results in terms of code quality.

DyNAVacS: an integrative tool for optimized DNA vaccine design

DNA vaccines have slowly emerged as keystones in preventive immunology due to their versatility in inducing both cell-mediated as well as humoral immune responses. The design of an efficient DNA vaccine, involves choice of a suitable expression vector, ensuring optimal expression by codon optimization, engineering CpG motifs for enhancing immune responses and providing additional sequence signals for efficient translation. DyNAVacS is a web-based tool created for rapid and easy design of DNA vaccines. It follows a step-wise design flow, which guides the user through the various sequential steps in the design of the vaccine. Further, it allows restriction enzyme mapping, design of primers spanning user specified sequences and provides information regarding the vectors currently used for generation of DNA vaccines. The web version uses Apache HTTP server. The interface was written in HTML and utilizes the Common Gateway Interface scripts written in PERL for functionality. DyNAVacS is an integrated tool consisting of user-friendly programs, which require minimal information from the user. The software is available free of cost, as a web based application at URL: .