Configurable highly available distributed services

The paper addresses the problem of providing highly available services in distributed systems. In particular, we examine the situation where a service may be used by a large continuously changing set of clients. The requirements for providing services in this environment are analysed and an architecture and partial implementation for a replicated server group meeting a range of client requirements is presented. The architecture facilitates the dynamic configuration management of the replicated server group, while maintaining the service. Dynamic configuration management is required in order to replace failed replicas, upgrade the server implementation, or change the availability characteristics of the service. The paper reports on initial implementation results.