Multi-Cache Coherence Protocol for Distributed Internet Services

1999

This paper presents a new approach for consistently caching dynamic Web data in order to improve performance. Our algorithm, which we call Data Update Propagation (DUP), maintains data dependence information between cached objects and the underlying data which affect their values in a graph. When the system becomes aware of a change to underlying data, graph traversal algorithms are applied to determine which cached objects are affected by the change. Cached objects which are found to be highly obsolete are then either invalidated or updated. DUP was a critical component at the official Web site for the 1998 Olympic Winter Games. By using DUP, we were able to achieve cache hit rates close to 100% compared with 80% for an earlier version of our system which did not employ DUP. As a result of the high cache hit rates, the Olympic Games Web site was able to serve data quickly even during peak request periods.

Proceedings of the 19th annual international conference on Supercomputing - ICS '05, 2005

We consider a cluster architecture in which dynamic content is generated by a database back-end and a collection of Web and application server front-ends. We study the effect of transparent query caching on the performance of such a cluster. Transparency requires that cached entries be invalidated as a result of writes. We start with a coarse-grain table-level automatic invalidation cache. Based on observed workload characteristics, we enhance the cache with the necessary dependency tracking and invalidations at the finer granularity of columns. Finally we reduce the miss penalty of invalidations through full and partial coverage of query results. In terms of system design, a query cache may be located at the database back-end, on dedicated machines, on the front-ends, or on a combination thereof. This paper evaluates the tradeoffs of the different cache designs and the cache location using the TPC-W benchmark.

In-memory read-only caches are widely used in cloud infrastructure to reduce access latency and to reduce load on backend databases. Operators view coherent caches as impractical at genuinely large scale and many clientfacing caches are updated in an asynchronous manner with best-effort pipelines.

International Journal of Computer Science and Engineering, 2017

Caching techniques has helped developers to deliver applications that are capable of fast turnaround time which otherwise could have been much slower and under-performed software solutions, less worthy of user's appreciation. Caching can typically be used at both hardware and software levels with the same ultimate goal of either achieving higher throughput or higher latency or both together. Limiting the subject to software level cache, the caching techniques could further be introduced in one of the two categories namely web cache and data cache. While web cache is often defined in the context of a browser which is a clientside application, the data cache is defined in the context of caching needs of a data extensive application. In terms of a database management system, it means a cache provisioned at the database services itself whereas, in the context of the application, it means the cache that spans through layers of the application, more precisely termed as tiers in a multi-tier application that is designed to cache an already queried data. The requirement of frequent data access in high volumes, in distributed applications, drives the need for more capable infrastructure towards building a caching framework. In this paper, we focus our discussion on data cache requirements of a distributed application and the key design factors that distinguish a distributed cache as an elegant cache service provider plugin to such distributed applications. We also propose a simplistic design that could be used to implement the core of a custom distributed cache.

The 8th International Conference on Communication Systems, 2002. ICCS 2002.

With exponential growth of the World Wide Web, techniques for alleviating the bottlenecks to network performance have gained increased importance. Web caching is one of such techniques which stores frequently used web objects nearer to the end user to reduce unnecessary remote access. As an evolving area in web caching, cooperative web caching has shown promising results over centralised caching mechanisms. This thesis makes several contributions to the area of cooperative web caching. We introduce a novel cooperative web caching architecture called Distributed Web Caching. Distributed Web Caching introduced here, is a variant of cooperative web caching. The novel feature in Distributed Web Caching is that every client node could act as a cache server and share its cache with neighboring nodes. A comprehensive set of protocols for access, storage and serving of distributed cached data is developed. We provide analytical models to evaluate and study of Distributed Web Caching. We implement the proposed architecture and measure the performance under different constraints. Further, we extend our analysis to object replacement strategies in Distributed Web Caching. We introduce simulation models to compare performance of object replacement strategies. Several novel replacement strategies for Distributed Web Caching are introduced and compared with existing stand-alone replacement strategies.

2003

The Web has become the primary means for information dissemination. It is ideal for publishing data residing in a variety of repositories, such as databases. In such a multi-tier system (client -Web server -underlying database), where the Web page content is dynamically derived from the database (Web-powered database), cache management is very important in making efficient distribution of the published information. Issues related to cache management are the cache admission/replacement policy, the cache coherency and the prefetching, which acts complementary to caching. The present chapter discusses the issues, which make the Web cache management radically different than the cache management in databases or operating systems. We present a taxonomy and the main algorithms proposed for cache replacement and coherence maintenance. We present three families of predictive prefetching algorithms for the Web and characterize them as Markov predictors. Finally, we give examples of how some popular commercial products deal with the issues regarding the cache management for Web-powered databases.

Computer Networks and …, 1998

An adaptive, highly scalable, and robust web caching system is needed to effectively handle the exponential growth and extreme dynamic environment of the World Wide Web. Our work presented last year sketched out the basic design of such a system. This sequel paper reports our progress over the past year. To assist caches making web query forwarding decisions, we sketch out the basic design of a URL routing framework. To assist fast searching within each cache group, we let neighbor caches share content information. Equipped with the URL routing table and neighbor cache contents, a cache in the revised design can now search the local group, and forward all missing queries quickly and efficiently, thus eliminating both the waiting delay and the overhead associated with multicast queries. The paper also presents a proposal for incremental deployment that provides a smooth transition from the currently deployed cache infrastructure to the new design.

In this paper, we propose a Caching Neighborhood Protocol (CNP) that describes an infrastructure upon which proxy servers can build dynamic caching hierarchies. Compared to the conventional schemes based on static caching hierarchies where proxy servers can only communicate with each other following pre- defined path configurations, the proposed dynamic scheme permits flexible communications among proxy servers. Such a scheme can decrease the response times of requests by increasing the availability of docu- ments without compromising the currency of rendered documents. CNP is based on the concept of caching neighborhood, in which originating servers extend their spans and availability through their caching repre- sentatives, incarnated as proxy servers. The coherence of documents provided by the originating server and the cached copies on its caching representatives is maintained via employing the X tolerance coherence requirement. Some qualitative reasonings and studies on the tra...

2006

In this paper, we present GlobeCBC, a content-blind query caching middleware for hosting Web applications in an edge computing infrastructure. Unlike existing data caching middleware systems, GlobeCBC stores the query results independently and does not merge different query results. We study the potential performance of this approach using extensive experimentations on our prototype implementation and compare it with other systems over an emulated wide-area network. Our evaluations show that content-blind caching performs well in terms of client latency for applications that exhibit high locality. It allows the system to sustain higher throughput by offloading the origin server database. We also present the design and evaluation of different online cache replacement algorithms for edge servers that have limited resource capabilities. In our evaluations, we find that the best heuristic must exploit temporal locality and take into account the query execution cost simultaneously.

2001

Abstract As World Wide Web usage has grown dramatically in recent years, so has grown the recognition that Web caches (especially proxy caches) will have an important role in reducing server loads, client request latencies, and network traffic. In this survey we present the most common architectures for web caching and their most important characteristics are outlined. These architectures include proxy caching, cooperative caching, adaptive caching, push caching and active caching.