1,721,143 research outputs found
Content adaptation architectures based on Squid proxy server
No full textThe overwhelming popularity of Internet and the technology advancements have determined the diffusion of many different Web-enabled devices. In such an heterogeneous client environment, efficient content adaptation and delivery services are becoming a major requirement for the new Internet service infrastructure. In this paper we describe intermediary-based architectures that provide adaptation and delivery of Web content to different user terminals. We present the design of a Squid-based prototype that carries out the adaptation of Web images and combines such a functionality with the caching of multiple versions of the same resource. We also investigate how to provide some form of cooperation among the nodes of the intermediary infrastructure, with the goal to evaluate to what extent the cooperation in discovering. adapting. and delivering Web resources can improve the user-perceived performance
Designing a broker for QoS-driven runtime adaptation of SOA applications
No full textOne of the major current trends in serviceoriented systems is the emphasis given to the need of introducingruntime adaptation features, so that the system can meet its QoS requirements in a volatile operating environment. In this paper we present the design and implementation of a service roker that supports the QoS-driven runtime adaptation of SOA applications offered as composite services to users. We describe the functionalities provided by the broker components and present their design and implementation according to two different versions we have developed and that are both based on open source products. The components of the first version have been developed in Java as Web services, while the second version takes advantage of OpenESB. Since the broker needs to sustain a traffic of requests generated by several concurrent users, we also present the replicated architectures of the two broker versions. We discuss the design tradeoffs and the lesson we have learned in developing the broker. © 2010 IEEE
Designing a flexible and modular architecture for a private cloud: A case study
No full textCloud computing is an emerging paradigm used by an increasingly number of enterprises to support their business and promises to make the utility computing model fully realized by exploiting virtualization technologies. Free software is now mature not only to offer well-known server-side applications, but also to land on desktop computers. However, administering in a decentralized way a large amount of desktop computers represents a demanding issue: system updates, backups, access policies, etc. are hard tasks to be managed separately on each computer. This paper presents a general purpose architecture for building a reliable, scalable, flexible, and modular private cloud that exploits virtualization technologies at different levels. The architecture can be used to offer a variety of services that span from web applications and web services to soft real-time applications. To show the features of the proposed architecture, we also present the design and implementation over it of a Linux Terminal Server Project (LTSP) cluster that benefits from the underlying IaaS services offered by the private cloud. The cloud infrastructure, as well as the LTSP, have been implemented exclusively using free software and are now in a production state, being used by approximately 200 users for their everyday work. We hope that our description and design decisions can provide some guidance about designing an architecture for a cloud service provider. Copyright © 2012 ACM
DNS dispatching algorithms with state estimators for scalable Web clusters
No full textReplication of information across a server cluster provides a promising way to support popular Web sites. However, a Web-server
cluster requires some mechanism for the scheduling of requests to the most available server. One common approach is to use the cluster
Domain Name System (DNS) as a centralized dispatcher. The main problem is that WWW address caching mechanisms (although
reducing network traffic) only let this DNS dispatcher control a very small fraction of the requests reaching the Web-server cluster. The
non-uniformity of the load from different client domains, and the high variability of real Web workload introduce additional degrees of
complexity to the load balancing issue. These characteristics make existing scheduling algorithms for traditional distributed systems not
applicable to control the load of Web-server clusters and motivate the research on entirely new DNS policies that require some system
state information. We analyze various DNS dispatching policies under realistic situations where state information needs to be estimated
with low computation and communication overhead so as to be applicable to a Web cluster architecture. In a model of realistic scenarios
for the Web cluster, a large set of simulation experiments shows that, by incorporating the proposed state estimators into the dispatching
policies, the effectiveness of the DNS scheduling algorithms can improve substantially, in particular if compared to the results of DNS
algorithms not using adequate state information
The 4th International Workshop on Autonomic Solutions for Parallel and Distributed Data Stream Processing (Auto-DaSP 2021)
No full textThe organizers of the 4th International Workshop on Autonomic Solutions for Parallel and Distributed Data Stream Processing (Auto-DaSP 2021) are delighted to welcome you to the workshop proceedings as part of the ICPE 2021 conference companion
Improving SOA applications response time with service overload detection
Full text linkSOA applications are usually built by assembling third-party software services. Even if each single service could offer a contract stating its non-functional properties, enforcing a monitoring policy is needed to detect services overload and consequent contract violations. In this paper we present a monitoring system capable of detecting service state changes. Our experimental results, obtained with a prototype, shows an improvement of 26% of the application response time
Towards self-adaptation planning for complex service-based systems
No full textA complex service-based system (CSBS), which comprises a multi-layer structure possibly spanning multiple organizations, operates in a highly dynamic and heterogeneous environment. At run time the quality of service provided by a CSBS may suddenly change, so that violations of the Service Level Agreements (SLAs) established within and across the boundaries of organizations can occur. Hence, a key management choice is to design the CSBS as a self-adaptive system, so that it can properly plan adaptation decisions to maintain the overall quality defined in the SLAs. However, the challenge in planning the CSBS adaptation is the uncertainty effect of adaptation actions that can variously affect the multiple layers of the CSBS. In a dynamic and constantly evolving environment, there is no guarantee that the adaptation action taken at a given layer can have an overall positive effect. Furthermore, the complexity of the cross-layer interactions makes the decision making process a non-trivial task. In this paper, we address the problem by proposing a multi-layer adaptation planning with local and global adaptation managers. The local manager is associated with a single planning model, while the global manager is associated with a multiple planning model. Both planning models are based on Markov Decision Processes (MDPs) that provide a suitable technique to model decisions under uncertainty. We present an example of scenario to show the practicality of the proposed approach
Generalized GEMM Kernels on GPGPUs: experiments and applications
No full textGeneral purpose computing on graphics processing units (GPGPU) is fast becoming a common feature of high performance computing centers. In this paper we discuss
some implementation issues related to dense linear algebra computations on GPUs, such as the GEneral Matrix-Matrix product, as well as other kernels sharing the same computational pattern, such as the matrix form of the All-Pairs Shortest-Path problem. Our CUDA implementation has shown a significant improvement on the NVIDIA processing units over the vendor's software. We review the optimization techniques that can be employed to implement such operations, as well as outline further development work in connected application domains
Evaluating User-perceived Benefits of Content Distribution Networks
No full textContent Distribution Networks (CDNs) are a class of successful content delivery architectures used by the most popular Web sites to enhance their performance. The basic idea is to address Internet bottleneck issues by replicating and caching the content of the customer Web sites and to serve it from the edge of the network. In this paper we evaluate to what extent the use of a CDN can improve the user-perceived response time. We consider a large set of scenarios with different network conditions and client connections, that have not been examined in previous studies. We found that CDNs can offer significative performance gain in normal network conditions, but the advantage of using CDNs can be reduced by heavy network traffic. Moreover, if CDN usage is not carefully designed, the achieved speedup can be suboptimal
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