David Capwell created CASSANDRA-19769:
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Summary: CEP-15: (Accord) sequence EpochReady.coordinating to
allow syncComplete to be learned from newer epochs
Key: CASSANDRA-19769
URL: https://issues.apache.org/jira/browse/CASSANDRA-19769
Project: Cassandra
Issue Type: Bug
Components: Accord
Reporter: David Capwell
When a node is bootstrapping or doing a host replacement it sees several epochs
before it actually joins the ring, but in Accord we only synchronize epoch
knowledge to the nodes that have already joined; this means we won’t ever
synchronize the epochs seen on the new nodes! This becomes a problem because it
forces these nodes to include far more epochs than required (because they don’t
know if the peers know the epoch), and may include stale epochs that are not
possible to reach quorum (such 2 host replacements to the same range would
cause that historic range to not be able to reach quorum).
By sequencing EpochReady.coordinating, we have the property that we only mark
sync complete for epoch=N if and only if epoch=N-1 has done it as well. With
this, peers are able to recover the past data when a new epoch is seen.
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