Replicating Web Applications On-Demand

August 3, 2004
Guillaume Pierre | Vrije Universiteit, Amsterdam

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 real-world 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.

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