Konstantin created CASSANDRA-15745:
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Summary: Conflicting LWT transactions may be committed during
topology change
Key: CASSANDRA-15745
URL: https://issues.apache.org/jira/browse/CASSANDRA-15745
Project: Cassandra
Issue Type: Bug
Components: Feature/Lightweight Transactions
Reporter: Konstantin
Let's consider a cluster which consists of replicas A, B and C.
We're adding replica D which replaces A.
A scenario is possible when two conflicting transactions, CAS1 and CAS2, may be
committed during replace:
CAS2 ballot > CAS1 ballot
CAS2 and CAS1 conflict on LWT condition, yet both of them may be committed in
case of the following sequence of events:
Topology change starts, advertises on C
CAS1 starts on node C, uses {A, B, C, D}
CAS2 starts on node A, still uses {A, B, C}
Topology change is advertised on A
CAS1 prepares on {B, C, D}
CAS2 prepares and accepts on {A, B}, commits on A
CAS1 accepts on D, then stops
Streaming starts, topology change finishes, A is removed
CAS3 prepares using C and D. It sees the accept of CAS1 and replays it
Both CAS1 and CAS2 are committed.
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