PS-11136: non-GTID transactions cause one storage flush per transaction, bypassing size/interval checkpointing#127
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…on, bypassing size/interval checkpointing https://perconadev.atlassian.net/browse/PS-11136 Problem: In non-GTID (anonymous transaction) replication mode, PBS flushes its in-memory event buffer to the storage backend on every transaction boundary, ignoring the configured 'checkpoint_size_bytes' and 'checkpoint_interval_seconds' thresholds. For object-store backends this turns into one PUT per transaction. Cause: 'storage::write_event()' had a fast-path keyed on 'at_transaction_boundary && transaction_gtid.is_empty()' whose intent was "flush regardless of thresholds because this is the file-final ROTATE/STOP event". The condition wasn't tight enough: anonymous transactions also satisfy it (they never populate 'transaction_gtid_'), so every XID terminating an anonymous transaction was misidentified as a file terminator and forced a synchronous flush. Solution: Removed the fast-path. The file-final ROTATE/STOP event is still flushed - just through the already-existing 'storage::close_binlog()' call on the 'process_rotate_or_stop_event()' / artificial-rotate rename paths, which is the natural place for a file-boundary flush. GTID-mode behavior is unchanged.
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Can we do better here. Maybe, make several attempts to grep the content of the PBS log file until we encounter something like next event position: <expected_position>
<expected_position> can be probably extracted from SHOW BINLOG EVENTS
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https://perconadev.atlassian.net/browse/PS-11136
Problem:
In non-GTID (anonymous transaction) replication mode, PBS flushes its in-memory event buffer to the storage backend on every transaction boundary, ignoring the configured 'checkpoint_size_bytes' and 'checkpoint_interval_seconds' thresholds. For object-store backends this turns into one PUT per transaction.
Cause:
'storage::write_event()' had a fast-path keyed on
'at_transaction_boundary && transaction_gtid.is_empty()' whose intent was "flush regardless of thresholds because this is the file-final ROTATE/STOP event". The condition wasn't tight enough: anonymous transactions also satisfy it (they never populate 'transaction_gtid_'), so every XID terminating an anonymous transaction was misidentified as a file terminator and forced a synchronous flush.
Solution:
Removed the fast-path. The file-final ROTATE/STOP event is still flushed - just through the already-existing 'storage::close_binlog()' call on the 'process_rotate_or_stop_event()' / artificial-rotate rename paths, which is the natural place for a file-boundary flush. GTID-mode behavior is unchanged.