Component replication in application servers

Three-tier middleware architecture is commonly used for hosting large-scale distributed applications. Typically the application is decomposed into three layers: front-end, middle tier and back-end. Front-end ("Web server") is responsible for handling user interactions and acts as a client of the middle tier, while back-end provides storage facilities for applications. Middle tier (' Application server') is usually the place where all computations are performed, so this layer provides middleware services for transactions, security and so forth. The benefit of this architecture is that it allows flexible configuration such as partitioning and clustering for improved performance and scalability. On this architecture, availability measures, such as replication, can be introduced in each tier in an application specific manner. Among the three tier described above, the availability of the middle tier and the back-end tier are the most important, as these tiers provide the computation and the data for the applications. This thesis investigates how replication for availability can be incorporated within the middle and back-end tiers. The replication mechanisms must guarantee exactly once execution of user request despite failures of application and database servers. The thesis develops an approach that requires enhancements to the middle tier only for supporting replication of both the tiers. The design, implementation and performance evaluation of such a middle tier based replication scheme for multi-database transactions on a widely deployed open source application server (1Boss) are presented.EThOS - Electronic Theses Online ServiceQUE Project, Department of Informatics, ITB, Bandung, IndonesiaGBUnited Kingdo

Geoprocessing Optimization in Grids

Geoprocessing is commonly used in solving problems across disciplines which feature geospatial data and/or phenomena. Geoprocessing requires specialized algorithms and more recently, due to large volumes of geospatial databases and complex geoprocessing operations, it has become data- and/or compute-intensive. The conventional approach, which is predominately based on centralized computing solutions, is unable to handle geoprocessing efficiently. To that end, there is a need for developing distributed geoprocessing solutions by taking advantage of existing and emerging advanced techniques and high-performance computing and communications resources. As an emerging new computing paradigm, grid computing offers a novel approach for integrating distributed computing resources and supporting collaboration across networks, making it suitable for geoprocessing. Although there have been research efforts applying grid computing in the geospatial domain, there is currently a void in the literature for a general geoprocessing optimization. In this research, a new optimization technique for geoprocessing in grid systems, Geoprocessing Optimization in Grids (GOG), is designed and developed. The objective of GOG is to reduce overall response time with a reasonable cost. To meet this objective, GOG contains a set of algorithms, including a resource selection algorithm and a parallelism processing algorithm, to speed up query execution. GOG is validated by comparing its optimization time and estimated costs of generated execution plans with two existing optimization techniques. A proof of concept based on an application in air quality control is developed to demonstrate the advantages of GOG

The architecture of discovery net : towards grid-based discovery services

Imperial Users onl

QoS control of E-business systems through performance modelling and estimation

E-business systems provide the infrastructure whereby parties interact electronically via business transactions. At peak loads, these systems are susceptible to large volumes of transactions and concurrent users and yet they are expected to maintain adequate performance levels. Over provisioning is an expensive solution. A good alternative is the adaptation of the system, managing and controlling its resources. We address these concerns by presenting a model that allows fast evaluation of performance metrics in terms of measurable or controllable parameters. The model can be used in order to (a) predict the performance of a system under given or assumed loading conditions and (b) to choose the optimal configuration set-up for certain controllable parameters with respect to specified performance measures. Firstly, we analyze the characteristics of E-business systems. This analysis leads to the analytical model, which is sufficiently general to capture the behaviour of a large class of commonly encountered architectures. We propose an approximate solution which is numerically efficient and fast. By mean of simulation, we prove that its accuracy is acceptable over a wide range of system configurations and different load levels. We further evaluate the approximate solution by comparing it to a real-life E-business system. A J2EE application of non-trivial size and complexity is deployed on a 2-tier system composed of the JBoss application server and a database server. We implement an infrastructure fully integrated on the application server, capable of monitoring the E-business system and controlling its configuration parameters. Finally, we use this infrastructure to quantify both the static parameters of the model and the observed performance. The latter are then compared with the metrics predicted by the model, showing that the approximate solution is almost exact in predicting performance and that it assesses the optimal system configuration very accurately.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Arquitecturas para sistemas de informação baseados em cloud computing

Mestrado em Engenharia dos Computadores e TelemáticaEste trabalho faz um apanhado do panorama actual no que diz respeito a Cloud computing. Começa por analisar a definição proposta pelo NIST e cate-gorizar vários serviços comerciais de acordo com as categorias propostas nes-sa definição. De seguida, são analisadas as implementações grátis disponíveis em licenças Open Source e chega-se à conclusão que para Clouds do tipo IaaS já existem várias implementações, algumas com boa qualidade, mas que na área de PaaS ainda existe muito trabalho a ser feito antes de se chegar a uma imple-mentação com funcionalidade comparável à dos serviços comerciais existen-tes. Após uma breve análise sobre a integração de SOA com as facilidades do Cloud computing, chegou-se à conclusão que PaaS se apresenta como o modelo de serviço mais adequando para desenvolver aplicações SOA. Visto que não existe ainda nenhum PaaS livre, e que os existentes apresentam problemas sérios de vendor lock in, é especificada uma framework completa, portátil e aberta que permitirá implementar um serviço do tipo PaaS em infra-estrutura privada ou sobre algum dos IaaS existentes. O PaaS especificado baseia-se, sempre que possível, em tecnologias existen-tes, concluindo-se que apenas a tecnologia de armazenamento de dados estruturados está aquém do necessário para a implementação. Deixa-se para o futuro a implementação dos vários módulos que permitirão a integração dos vários componentes da PaaS, no entanto sempre que possível, são sugeridas tecnologias a utilizar de forma a manter a implementação aberta e portátil.This work sums up the current situation of Cloud computing. It starts by per-forming an analysis of the NIST definition draft, and categorizing some com-mercial services into the categories proposed by the referred definition. Next, the free implementations distributed under an Open Source license are analyzed, and the conclusion is that there are some high quality IaaS cloud implementations, but the PaaS area still needs a lot of work before the functio-nality of a free implementation is comparable to that of the commercial services available. After a brief analysis of the integration of SOA and Cloud computing, the con-clusion is that PaaS presents the most adequate service model for the devel-opment of SOA applications. Given that, up to the moment, there is no free PaaS, and that the existing ones present serious vendor lock in problems, a complete, portable, and open framework that allows the deployment of a PaaS type service on private or on IaaS infrastructure is specified. The specified PaaS is based on current technology whenever possible, with exception of the storage of structured data that is not up to the requirements yet. The implementation of the modules required to integrate the various PaaS components is left as future work. Yet, whenever possible, suggestions are made about usable technologies that will allow the PaaS to remain portable and open

Proof-of-Concept Application - Annual Report Year 1

In this document the Cat-COVITE Application for use in the CATNETS Project is introduced and motivated. Furthermore an introduction to the catallactic middleware and Web Services Agreement (WS-Agreement) concepts is given as a basis for the future work. Requirements for the application of Cat-COVITE with in catallactic systems are analysed. Finally the integration of the Cat-COVITE application and the catallactic middleware is described. --Grid Computing

Real-Time intelligence

Dissertação de mestrado em Computer ScienceOver the past 20 years, data has increased in a large scale in various fields. This explosive increase of global data led to the coin of the term Big Data. Big data is mainly used to describe enormous datasets that typically includes masses of unstructured data that may need real-time analysis. This paradigm brings important challenges on tasks like data acquisition, storage and analysis. The ability to perform these tasks efficiently got the attention of researchers as it brings a lot of oportunities for creating new value. Another topic with growing importance is the usage of biometrics, that have been used in a wide set of application areas as, for example, healthcare and security. In this work it is intended to handle the data pipeline of data generated by a large scale biometrics application providing basis for real-time analytics and behavioural classification. The challenges regarding analytical queries (with real-time requirements, due to the need of monitoring the metrics/behavior) and classifiers’ training are particularly addressed.Nos os últimos 20 anos, a quantidade de dados armazenados e passíveis de serem processados, tem vindo a aumentar em áreas bastante diversas. Este aumento explosivo, aliado às potencialidades que surgem como consequência do mesmo, levou ao aparecimento do termo Big Data. Big Data abrange essencialmente grandes volumes de dados, possivelmente com pouca estrutura e com necessidade de processamento em tempo real. As especificidades apresentadas levaram ao aparecimento de desafios nas diversas tarefas do pipeline típico de processamento de dados como, por exemplo, a aquisição, armazenamento e a análise. A capacidade de realizar estas tarefas de uma forma eficiente tem sido alvo de estudo tanto pela indústria como pela comunidade académica, abrindo portas para a criação de valor. Uma outra área onde a evolução tem sido notória é a utilização de biométricas comportamentais que tem vindo a ser cada vez mais acentuada em diferentes cenários como, por exemplo, na área dos cuidados de saúde ou na segurança. Neste trabalho um dos objetivos passa pela gestão do pipeline de processamento de dados de uma aplicação de larga escala, na área das biométricas comportamentais, de forma a possibilitar a obtenção de métricas em tempo real sobre os dados (viabilizando a sua monitorização) e a classificação automática de registos sobre fadiga na interação homem-máquina (em larga escala)