Under high-concurrency MySQL load, uvicorn cancels request tasks when
clients disconnect. If cancellation lands mid-query, session.close()
tries to ROLLBACK on a connection that aiomysql has already marked as
closed — raising InterfaceError("Cancelled during execution") and
leaving the connection checked-out until GC, which the pool then
warns about as a 'non-checked-in connection'.
The old fallback tried sync.rollback() + sync.close(), but those still
go through the async driver and fail the same way on a dead connection.
Replace them with session.sync_session.invalidate(), which just flips
the pool's internal record — no I/O, so it can't be cancelled — and
tells the pool to drop the connection immediately instead of waiting
for garbage collection.
anti
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