FLUSH PRIMITIVES FOR ASYNCHRONOUS DISTRIBUTED SYSTEMS

We present three channel primitives for sending messages: two-way-flush, forward-flush, and backward-flush, collectively termed Flush. A non-FIFO channel that supports Flush will be termed an F-channel. F-channels can permit as much concurrency as non-FIFO channels and yet retain the properties of FIFO channels that lead to simplicity of reasoning in design and proofs of correctness of distributed algorithms. We illustrate these claims using examples of distributed algorithms for taking global snapshots and in the process we also illustrate that use of these primitives weaker definition of a channel state compared to defining it as a sequence of messages. © 1990.