Distributed Wikis on Structured Overlays

We present a transaction processing scheme for structured overlay networks and use it to develop a distributed Wiki application that is based on a relational data model. The Wiki supports rich metadata and additional indexes for navigation purposes. Ensuring consistency and durability requires handling of node failures. We mask such failures by providing high availability of nodes by constructing the overlay from replicated state machines (Cell Model). Atomicity is realized using two phase commit with additional support for failure detection and restoration of the transaction manager. The developed transaction processing schema provides the application with a mixture of pessimistic, hybrid optimistic and multiversioning concurrency control techniques to minimize the impact of replication on latency and optimize for read operations. We present pseudocode of the relevant Wiki functions and evaluate the different concurrency control techniques in terms of message complexity.