Group communication systems are powerful building blocks that
facilitate the development of fault-tolerant distributed applications. Such
systems generally run in an asynchronous fault-prone environment, and provide
semantics (called Virtual Synchrony) that mask the asynchrony and unreliability
of the environment. In order to implement Virtual Synchrony semantics, group
communication systems typically impose blocking periods during which
applications are not allowed to send messages. This paper presents a novel form
of group communication, Optimistic Virtual Synchrony (OVS). OVS allows
applications to send messages during periods in which existing group
communication services block, by making optimistic assumptions on the network
connectivity. Optimistic Virtual Synchrony allows applications to determine the
policy as to when messages sent optimistically should be delivered and when
they should be discarded. Thus, OVS gives applications fine-grain control over
the specific semantics they require, and does not impose costs for enforcing
any semantics that they do not require. At the same time, OVS provides a single
easy-to-use interface for all applications. The paper presents several examples
of applications that may exploit OVS and empirical results that show the
performance benefits of using OVS.
Pre-2018 CSE ID: CS1999-0634