On Wednesday, August 14, I'll be giving a livestreamed talk with @fauna, discussing various approaches for transactional isolation in globally distributed systems, including Spanner, @CockroachDB, FaunaDB, @YugaByteDB, @VoltDB, Percolator, and TiDB.http://www2.fauna.com/wcdistributedarchitectures …
Oh, I think I get what you're driving at here. Yes, I think you need to get a commit index, and specifically, one for the decision to seal the log window, but I don't think that's in the blocking path of txns--if you couple windows to the Raft term, leader can seal independently
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... one thing I hadn't considered until now, though, was that if we assume clocks perfectly synced, and all nodes seal simultaneously, yes, you do need to wait a third inter-dc hop for remote leaders to inform you of the window being sealed...
@fauna, care to jump in here? -
Fauna varies from RAFT here: followers learn of commit from a quorum of peers. In a 3 replica cluster, a remote replica can seal an epoch after one WAN hop, since it only needs to hear from the leader and itself. W/ more than 3 nodes, this increases to 2 hops.
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