Data distribution techniques for load-balanced fault-tolerant web access

摘要

A server system for processing client requests received over a communication network includes a cluster of N document servers and at least one redirection server. The redirection server receives a client request from the network and redirects it to one of the document servers, based on a set of pre-computed redirection probabilities. Each of the document servers may be an HTTP server that manages a set of documents locally and can service client requests only for the locally-available documents. A set of documents are distributed across the document servers in accordance with a load distribution algorithm which may utilize the access rates of the documents as a metric for distributing the documents across the servers and determining the redirection probabilities. The load distribution algorithm attempts to equalize the sum of the access rates of all the documents stored at a given document server across all of the document servers. In the event of a server failure, the redirection probabilities may be recomputed such that the load of client requests is approximately balanced among the remaining document servers. The redirection probabilities may also be recomputed periodically in order to take into account changes in document access rates and changes in server capacity. The recomputation may be based on a maximum-flow minimum-cost solution of a network flow problem.