V21.11.x backport pr3232: Abort transactions with same pid but older epoch when detected #3247
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rm_stm is a replicated state machine running on top of a Redpanda data partition so we may break down an execution of a command in a familiar sequence of steps: 1) validation 2) replication 3) catching up 4) execution After replication is over we know than it won't be lost and for some commands we may decide to return before waiting for step four. But in this case when we process the next command we can't be sure that it sees an up to date state. Caching the replicated offset available after step 2 to use it later (during an execution of the abort & commit commands) to explicitly check / wait the previously replicated command is already executed (cherry picked from commit 51f42c1)
kafka clients use producer id as an identity and not pid & epoch as we assumed before, so when we postponed writing an abort marker with older epoch. it could accidentally abort more txes than needed even when they had different (fresher) pid & epoch pair fixing the problem by writing an abort marker as soon as new epoch (with the same pid) is detected (cherry picked from commit e312dd1)
dotnwat
approved these changes
Dec 13, 2021
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Cover letter
Backport #3232
Release notes
Fixes a consistency issue with transactions