Efficient Message Logging for Uncoordinated Checkpointing Protocols
Abstract
A message is {\it in-transit} with respect to a global state if its sending is recorded in this global state, while its receipt is not. Checkpointing algorithms have to log such in-transit messages in order to restore the state of channels when a computation has to be resumed from a consistent global state after a failure has occurred. Coordinated checkpointing algorithms log those in-transit messages exactly on stable storage. Because of their lack of synchronization, uncoordinated checkpointing algorithms conservatively log more messages. This paper presents an uncoordinated checkpointing protocol that logs all in-transit messages and the smallest possible number of non in-transit messages. As a consequence, the protocol saves stable storage space and enables quicker recoveries. An appropriate tracking of message causal dependencies constitutes the core of the protocol.
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