[v24.2.x] Fixed race condition between appends and prefix truncation #24329
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Adding a stress fiber to the test executing appends and concurrently prefix truncation allows to easily trigger any race condition bugs. Signed-off-by: Michał Maślanka <michal@redpanda.com> (cherry picked from commit 73fdfe1)
The race condition between prefix truncation and appends was leading to an issue in which the same offset might have been assigned twiice to batches that were appended to log. This invalidates the invariant and may lead to inconsistencies. The fix has two parts. The first part fixes calculation of next offset for the newly created log appender. Previously the check incorrectly validated if the log is empty. The condition was simplified and it is now based on an invariant that if the `start_offset > dirty_offset` the log is empty (there is one exception to it when the log is empty and first initialized, but then the next offset is derived as usual by incrementing the dirty offset). The second part of the fix is an addition of check if the segment is still removable after the segment write lock was acquired for its removal. It is perfectly viable scenario that when the prefix truncation fiber is waiting for the lock the segment is written to. In this case the segment should not be removed as it contains valid data. Signed-off-by: Michał Maślanka <michal@redpanda.com> (cherry picked from commit 3709f81)
piyushredpanda
approved these changes
Nov 27, 2024
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Backport of PR #24306