Replicating Web Applications On-Demand

Many Web-based commercial services deliver their content using Web applications that generate pages dynamically based on user profiles, request parameters etc. The workload of these applications are often characterized by a large number of unique requests and a significant fraction of data updates. Hosting these applications drives the need for systems that replicates both the application code and its underlying data. We propose the design of such a system that is based on on-demand replication, where data units are replicated only to servers that access them often. This reduces the consistency overhead as updates are sent to a reduced number of servers. The proposed system allows complete replication transparency to the application, thereby allowing developers to build applications unaware of the underlying data replication. We show that the proposed techniques can reduce the client response time by a factor of 5 in comparison to existing techniques for a realworld e-commerce application used in the TPC-W benchmark. Furthermore, we evaluate our strategies for a wide range of workloads and show that on-demand replication performs better than centralized and fully replicated systems by reducing the average latency of read/write data accesses as well as the amount of bandwidth utilized to maintain data consistency. 1

CloudTPS: Scalable Transactions for Web Applications in the Cloud

NoSQL Cloud data services provide scalability and high availability properties for web applications but at the same time they sacrifice data consistency. However, many applications cannot afford any data inconsistency. CloudTPS is a scalable transaction manager to allow cloud database services to execute the ACID transactions of web applications, even in the presence of server failures and network partitions. We implement this approach on top of the two main families of scalable data layers: Bigtable and SimpleDB. Performance evaluation on top of HBase (an open-source version of Bigtable) in our local cluster and Amazon SimpleDB in the Amazon cloud shows that our system scales linearly at least up to 40 nodes in our local cluster and 80 nodes in the Amazon cloud

Adaptive Replicated Web Documents.

Caching and replication techniques can improve latency of the Web, while reducing network traffic and balancing load among servers. However, no single strategy is optimal for replicating all documents. Depending on its access pattern, each document should use the policy that suits it best. This paper presents an architecture for adaptive replicated documents. Each adaptive document monitors its access pattern, and uses it to determine which strategy it should follow. When a change is detected in its access pattern, it re-evaluates its strategy to adapt to the new conditions. Adaptation comes at an acceptable cost considering to the benefits of per-document replication strategies. vrije Universiteit Faculty of Mathematics and Computer Science 1 Introduction Most Web users suffer from slow document transfers. The reasons for such high latencies include distance between the user and the document, and load of the intermediate network. One common solution is to maintain copies of ..

Coordinated Self-Adaptation in Large-Scale Peer-to-Peer Overlays

Self-adaptive systems typically rely on a closed control loop which detects when the current behavior deviates too much from the optimal one, determines new optimal values for system parameters, and applies changes to the system configuration. In decentralized systems, implementing each of these steps is challenging, especially when nodes need to coordinate their local configurations. In this paper, we propose a decentralized method to automatically tune global system parameters in a coordinated manner. We use gossip-based protocols to continuously monitor system properties and to disseminate parameter updates. We show that this method applied to a decentralized resource selection service allows the system to quickly adapt to changes in workload types and node properties, and only incurs a negligible communication overhead

ConPaaS: a Platform for Hosting Elastic Cloud Applications

ConPaaS is an open source platform-as-a-service environment that aims at simplifying the deployment of cloud applications. In ConPaaS, an application is defined as a composition of one or more services. Each service is self-managed and elastic: it can deploy itself on the cloud, monitor its own performance, and increase or decrease its processing capacity through dynamic resource provisioning. © 2012 IEEE

Globule: A Collaborative Content Delivery Network

We present Globule, a collaborative content delivery network developed by our research group. Globule is composed of Web servers that cooperate across a wide area network to provide performance and availability guarantees to the sites they host. We discuss the issues involved in developing and setting up a large-scale collaborative CDN and provide solutions for many of its unique problems. © 2006 IEEE