Membership and System Diagnosis

A membership service is a service in a distributed system that maintains and provides information about which sites are functioning and which have failed at any given time. System diagnosis, on the other hand, is a method for detecting faulty processing elements and distributing this information to non-faultyelements. In spite of the apparent similarity of goals, these two fields have been considered separately from their beginnings. In this paper, we attempt to compare these fields and show the fundamental differences and the similarities. We demonstrate that the problems are closely related, with the major differences being the assumptions made about the failure model, the testing methods, and the type of service guarantees provided to the application. Furthermore, we demonstrate that the fields are closely enough related that some algorithms utilized in one field can easily be transformed into algorithms in the other. As examples, we derive new membership algorithms from a distributed system diagnosis algorithm and new system diagnosis algorithms from membership algorithms.