Helen M. Thomas

Proxy-based acceleration of dynamically generated content on the world wide web: An approach and implementation

As Internet traffic continues to grow and websites become increasingly complex, performance and scalability are major issues for websites. Websites are increasingly relying on dynamic content generation applications to provide website visitors with dynamic, interactive, and personalized experiences. However, dynamic content generation comes at a cost---each request requires computation as well as communication across multiple components.To address these issues, various dynamic content caching approaches have been proposed. Proxy-based caching approaches store content at various locations outside the site infrastructure and can improve website performance by reducing content generation delays, firewall processing delays, and bandwidth requirements. However, existing proxy-based caching approaches either (a) cache at the page level, which does not guarantee that correct pages are served and provides very limited reusability, or (b) cache at the fragment level, which is associated with several design-level and runtime scalability issues. To address these issues, several back-end caching approaches have been proposed, including query result caching and fragment level caching. While back-end approaches guarantee the correctness of results and offer the advantages of fine-grained caching, they neither address firewall delays nor reduce bandwidth requirements.In this article, we present an approach and an implementation of a dynamic proxy caching technique which combines the benefits of both proxy-based and back-end caching approaches, yet does not suffer from their above-mentioned limitations. Our dynamic proxy caching technique allows granular, proxy-based caching in highly dynamic scenarios, accessible outside the site infrastructure. We present two possible configurations for our dynamic proxy caching technique: (1) a reverse proxy configuration, and (2) a forward proxy configuration. Analysis of the performance of our approach indicates that it is capable of providing significant reductions in bandwidth. We have deployed our proposed dynamic proxy caching technique at a major financial institution. The results of this implementation indicate that our technique is capable of providing up to 3x reductions in bandwidth and response times in real-world dynamic Web applications when compared to existing caching solutions.

Proxy-based acceleration of dynamically generated content on the world wide web: an approach and implementation

As Internet traffic continues to grow and web sites become increasingly complex, performance and scalability are major issues for web sites. Web sites are increasingly relying on dynamic content generation applications to provide web site visitors with dynamic, interactive, and personalized experiences. However, dynamic content generation comes at a cost --- each request requires computation as well as communication across multiple components.To address these issues, various dynamic content caching approaches have been proposed. Proxy-based caching approaches store content at various locations outside the site infrastructure and can improve Web site performance by reducing content generation delays, firewall processing delays, and bandwidth requirements. However, existing proxy-based caching approaches either (a) cache at the page level, which does not guarantee that correct pages are served and provides very limited reusability, or (b) cache at the fragment level, which requires the use of pre-defined page layouts. To address these issues, several back end caching approaches have been proposed, including query result caching and fragment level caching. While back end approaches guarantee the correctness of results and offer the advantages of fine-grained caching, they neither address firewall delays nor reduce bandwidth requirements.In this paper, we present an approach and an implementation of a dynamic proxy caching technique which combines the benefits of both proxy-based and back end caching approaches, yet does not suffer from their above-mentioned limitations. Our dynamic proxy caching technique allows granular, proxy-based caching where both the content and layout can be dynamic. Our analysis of the performance of our approach indicates that it is capable of providing significant reductions in bandwidth. We have also deployed our proposed dynamic proxy caching technique at a major financial institution. The results of this implementation indicate that our technique is capable of providing order-of-magnitude reductions in bandwidth and response times in real-world dynamic Web applications.

A case for parallelism in data warehousing and OLAP

In recent years the database community has experienced a tremendous increase in the availability of new technologies to support efficient storage and retrieval of large volumes of data, namely data warehousing and On-Line Analytical Processing (OLAP) products. Efficient query processing is critical in such an environment, yet achieving quick response times with OLAP queries is still largely an open issue. We propose a solution approach to this problem by applying parallel processing techniques to a warehouse environment. We suggest an efficient partitioning strategy based on the relational representation of a data warehouse (i.e., star schema). Furthermore, we incorporate a particular indexing strategy, DataIndexes, to further improve query processing times and parallel resource utilization, and propose a preliminary parallel star-join strategy.

World Wide Wait: A Study of Internet Scalability and Cache-Based Approaches to Alleviate It

The Internet is growing rapidly in terms of both use and infrastructure. Unfortunately, demand is outpacing the capacity of the infrastructure, as evidenced by unacceptably long response times. To support current load and further growth, we must address this problem. Several caching strategies have been proposed in the literature; many have been implemented to improve the quality of service on the Web. In this paper, we identify the main causes of delay on the Web, and provide a review of the various caching strategies employed to mitigate these delays. We also survey the application of Operations Research/Management Science (OR/MS) techniques to caching on the Web. Finally, we identify several open OR/MS research problems related to Web caching.

FUSION: a system allowing dynamic Web service composition and automatic execution

Service portals are systems which expose a bundle of Web services to the user, allowing the specification and subsequent execution of complex tasks defined over these individual services. Examples of situations where service portals would be valuable include making travel plans or purchasing a home. Service portals must be capable of converting an abstract user goal into a correct and optimal concrete execution plan, executing according to the plan, verifying the result against a users stated satisfaction criteria, and in the case of satisfaction failure, initiating the appropriate recovery procedures. The basic framework needed to support this functionality, from gathering the input to generating an optimal plan and executing that plan, is a prerequisite for all service portals, yet there are currently no such commercial systems in existence, and the research literature has given only cursory treatment to some of these issues. In this paper, we describe FUSION, a comprehensive software system which provides the underlying framework for a service portal. We show how using the elements of this framework, service portal designers and architects can easily create domain-specific service portals, e.g., a travel service portal. We also present the Web services execution specification language (WSESL), a language that we have developed to describe execution plans in the context of the FUSION services model. Finally, we develop a set of data structures and algorithms for generating correct and optimal execution plans.

Accelerating dynamic Web content generation

As a middle-tier, server-side caching engine, the dynamic content accelerator reduces dynamic page-generation processing delays by caching fragments of dynamically generated Web pages. This fragment-level solution, combined with intelligent cache management strategies, can significantly reduce the processing load on the Web application server, letting it handle higher user loads and thus significantly outperforming existing middle-tier caching solutions.

ReDAL: An Efficient and Practical Request Distribution Technique for Application Server Clusters

Modern Web-based application infrastructures are based on clustered multitiered architectures, where request distribution occurs in two sequential stages: over a cluster of Web servers and over a cluster of application servers. Much work has focused on strategies for distributing requests across a Web server cluster in order to improve the overall throughput across the cluster. The strategies applied at the application layer are the same as those at the Web server layer because it is assumed that they transfer directly. In this paper, we argue that the problem of distributing requests across an application server cluster is fundamentally different from the Web server request distribution problem due to core differences in request processing in Web and application servers. We devise an approach for distributing requests across a cluster of application servers such that the overall system throughput is enhanced, and load across the application servers is balanced.

A proxy-based approach for dynamic content acceleration on the WWW

Various dynamic content caching approaches have been proposed to address the performance and scalability problems faced by many Web sites that utilize dynamic content generation applications. Proxy-based caching approaches store content at various locations outside the site infrastructure and can improve Web site performance by reducing content generation delays, firewall processing delays, and bandwidth requirements. However, existing proxy-based caching approaches either: (a) cache at the page level, which does not guarantee that correct pages are served and provides very limited reusability, or (b) cache at the fragment level, which requires the use of pre-defined page layouts. To address these issues, several back end caching approaches have been proposed, including query result caching and fragment level caching. While back end approaches guarantee the correctness of results and offer the advantages of fine-grained caching, they neither address firewall delays nor reduce bandwidth requirements. The authors present an approach and an implementation of a dynamic proxy caching technique which combines the benefits of both proxy-based and back end caching approaches, yet does not suffer from their above-mentioned limitations.

Linearized Model of Object Caching and Heuristic Solution

Object-oriented (OO) technologies have become widely adopted in enterprise applications due to the additional functionality and flexibility they provide to these applications. At the same time, however, OO technologies also require significant amounts of computational power to support, greatly impacting the performance and scalability of such applications. A very popular solution to mitigate this problem is object caching. In this paper, we show how the application of object caching maps into an optimization problem. In particular, we focus on the design-time decision of determining which objects should be candidates for caching. Choosing the cacheable objects is an important decision since it can have a significant impact on application performance. We formulate this problem as a linear integer program and present a heuristic solution approach. We also demonstrate, through a set of experiments, that our heuristic provides solutions that are reasonably close to optimal. Our contribution is a model and an efficient solution approach for this model that can help application developers to make more informed cacheability decisions and thereby improve application performance and scalability.