Message Logging: Pessimistic, Optimistic, Causal, and Optimal

13 years 4 months ago

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Message-logging protocols are an integral part of a popular technique for implementing processes that can recover from crash failures. All message-logging protocols require that, when recovery is complete, there be no orphan processes, which are surviving processes whose states are inconsistent with the recovered state of a crashed process. We give a precise speci cation of the consistency property \no orphan processes". From this speci cation, we describe how di erent existing classes of message-loggingprotocols (namely optimistic, pessimistic, and a class that we call causal) implement this property. We then propose a set of metrics to evaluate the performance of message-logging protocols, and characterize the protocols that are optimal with respect to these metrics. Finally, starting from a protocol that relies on causal delivery order, we show how to derive optimal causal protocols that tolerate f overlapping failures and recoveries for a parameter f : 1 f n.

Lorenzo Alvisi, Keith Marzullo

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