Template-Based Runtime Invalidation for Database-Generated Web Contents

We propose a template based runtime invalidation approach for maintaining cache consistency of database generated web contents. In our approach, the invalidator sits between a web cache and a database server, and intercepts query statements as well as update statements transparently. Moreover, it maintains templates for queries and updates, as well as a mapping between URLs and SQL queries. At runtime, the invalidator checks an update statement against the query statements whose corresponding HTML fragments have been cached, and decides on if any cached HTML fragments should be invalidated based on an extended satisfiability testing algorithm without sending any polling queries to the backend database. We further improve the efficiency of this checking process by utilizing the semantic information of the templates. We have integrated our invalidator with the Oracle Web Cache and have conducted extensive experiments using the TPC-W benchmark. Our results show that this approach efficiently maintains the consistency of cached HTML fragments with the backend database.