[v26.1.x] group/tx/stm: limit local snapshot to max_removable_local_log_offset#30080
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bharathv merged 2 commits intoredpanda-data:v26.1.xfrom Apr 9, 2026
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(cherry picked from commit ede6621)
The group_tx_tracker_stm snapshot could capture open transaction state (begin_offsets/producer_states) at an offset where the corresponding commit batch had not yet been written. If compaction later removed that commit batch — which is allowed once max_removable_offset advances past it — the open transaction could never be resolved on restart, permanently blocking max_removable_offset and preventing further compaction. The sequence: 1. Snapshot taken while a tx is open (fence at F, snapshot offset >= F) 2. Tx commits at offset C, max_removable advances past C 3. Compaction removes the commit batch at C 4. On restart, snapshot loads stale open tx at F, replay cannot find the commit -> max_removable stuck at prev(F) forever Fix: snapshot at max_removable_local_log_offset with an empty transactions map. Since this STM's sole purpose is tracking open transactions for max_removable_local_log_offset, and closed transactions leave no state, all meaningful state can be reconstructed from log replay. Open transactions are re-discovered from fence batches in the log, which are guaranteed to be present since compaction is bounded by max_removable while the STM is live. Also adds a regression test that reproduces the scenario by taking a snapshot during an open tx, committing, compacting, re-persisting the stale snapshot, and restarting. To fix existing setups that have stale snapshots, this commit also bumps supported_local_snapshot_version, this invalidates saved snapshots upon upgrade and applies everything from log and reconstructs the correct snapshots the next time with the newer logic. (cherry picked from commit 45fff0d)
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Converting to draft temporarily so the main change gets some bake time, please don't merge. |
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CI test resultstest results on build#82788
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bharathv
approved these changes
Apr 9, 2026
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Backport of PR #30071