Automatic Replication for Web Applications

Abstract

This chapter proposes a software architecture to enhance the availability of Web-based applications at a reasonable cost. The architecture is pluggable to existing Web-applications, so that no modifications are required to existing code. There are no specific hardware or server software requirements. Availability is achieved by replication, and strong replica consistency is automatically guaranteed by using off-the-shelf group communication components. The proposed architecture is explained in detail, and it is compared against some of the most relevant highly-available solutions used nowadays. The most distinctive feature of the proposed architecture is that it explicitly addresses replica consistency, providing automatic strong replica consistency. Besides automatic consistency, attention is given to simplicity and pluggability.