Ariel Weisberg created CASSANDRA-13419:
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Summary: Relax limit on number of pending endpoints during CAS
Key: CASSANDRA-13419
URL: https://issues.apache.org/jira/browse/CASSANDRA-13419
Project: Cassandra
Issue Type: Improvement
Components: Coordination, CQL
Reporter: Ariel Weisberg
Assignee: Ariel Weisberg
CASSANDRA-8346 avoids stale reads during CAS when checking the condition or
doing serial reads by disallowing more than one pending endpoint.
It seems like it should be possible to allow more than one pending endpoint by
being smarter about who we read from during the QUORUM read or about the state
of pending nodes that are there for host replacement.
Sylvain suggested
bq. Well, I guess things are working as they do for decently good reason here.
That said, thinking about it, it could be that the solution from CASSANDRA-8346
is a bit of a big hammer: I believe it's enough to ensure that we read from at
least one replica that responded to PREPARE 'in the same Paxos round' But we
have timeouts on the paxos round, so it could be it is possible to reduce
drastically the time we consider a node pending for CAS so that it's not a real
problem in practice. Something like having pending node move to a "almost
there" state before becoming true replica, and staying in that state for
basically the max time of a paxos round, and then Paxos might be able to
replace "pending" nodes by those "almost there" for PREPARE.
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