Comment by Jach

This has been a fun thread to read, though not reflecting highly on HN. For what it's worth, I agree with you that the original adage kicking this off is kind of silly, and basically wrong. For further enjoyment I found this interesting blog post from another PhD that addresses things more comprehensively (and also basically agrees with you): https://www.mydistributed.systems/2021/10/exactly-once-deliv...

The opening lines include: "The exact definition, however, is not agreed upon in the community. As a result, there is a debate on whether EOD is possible or impossible to achieve." If nothing else, I and probably others learned today that this is apparently a debate that can quickly turn into a flamewar. And I thought flamewars were mostly dead!

Another interesting paper that came up, as I have an interest in TLA+ proofs: "LogPlayer: Fault-tolerant Exactly-once Delivery using gRPC Asynchronous Streaming" https://arxiv.org/abs/1911.11286 It seems there's no problem in the community to do things like prove fault-tolerant exactly-once delivery, even if such terminology isn't universally agreed on.