Application specific data replication for edge services

Application Specific Data Replication for Edge Services

Lei Gao,Mike Dahlin,Amol Nayate,

Jiandan Zheng

Laboratory for Advanced Systems Research Department of Computer Sciences

The University of T exas at Austin

lgao,dahlin,nayate,zjiandan

@

Arun Iyengar

IBM T.J.Watson Research Center

P.O.Box704

Y orktown Heights,NY10598 aruni@

Abstract

The emerging edge services architecture promises to improve the availability and performance of web services by replicating servers at geographically distributed sites.A key challenge in such systems is data replication and consistency so that edge server code can ma-nipulate shared data without incurring the availability and perfor-mance penalties that would be incurred by accessing a traditional centralized database.This paper explores using a distributed ob-ject architecture to build an edge service system for an e-commerce application,an online bookstore represented by the TPC-W bench-mark.We take advantage of application specific semantics to de-sign distributed objects to manage a specific subset of shared in-formation using simple and effective consistency models.Our ex-perimental results show that by slightly relaxing consistency within individual distributed objects,we can build an edge service system that is highly available and efficient.For example,in one experi-ment wefind that our object-based edge server system provides a factor offive improvement in response time over a traditional cen-tralized cluster architecture and a factor of nine improvement over an edge service system that distributes code but retains a central-ized database.

1.INTRODUCTION

The emerging edge services architecture for providing web ser-vices processes client requests at a collection of edge servers dis-tributed across the network and near end users[1,5,8,35,38].This approach minimizes communication across the wide area network during the processing of client requests in order to improve service availability and latency.

Improving availability and latency is crucial for business-critical e-commerce servers.Although some server vendors advertise“four-9’s”(99.99%)or“five-9’s”(99.999%)of availability,when net-work failures are considered,end-to-end service availability is of-ten as low as two-9’s(99%),meaning that an average web client cannot contact an average web server for about15minutes a day[15, 28,44].Furthermore,despite that Internet web server response times have been improved,human factors studies suggest that hu-man productivity improves more than linearly as computer systems response times fall in the sub-second range[21].

Many systems for business logic(code)distribution and exe-