An open commit protocol preserving consistency in the presence of commission failures

Abstract

Most of the proposed commit protocols assume that all participants of a transaction are sane, i.e., they only fail with omission failures and eventually recover. Unfortunately, this assumption is not realistic for open distributed systems (ODSs), which can be divided into a trusted and a nontrusted domain. While nodes in the trusted domain are assumed to be sane, nontrusted nodes may fail permanently and with commission failures. The open commit protocols presented are based on a model for consistency checking. The protocol also tolerates any number of commission failures in the nontrusted domain of an ODS. It guarantees that the trusted participants of a transaction terminate in a way that preserves consistency in the trusted domain, which generally does not mean that all trusted participants have to terminate consistently. The protocol groups those trusted participants that have to terminate consistently to maintain data consistency, and ensures that in each group the participants terminate in the same way. The advantages of the protocol are a simplified commit processing and a reduced message complexity. The message complexity of this protocol exceeds that of traditional two-phase commit protocols by no more than two messages for most practical cases.<>