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close_all_connections() only disposes the engine's connection pool —
asyncio tasks like print_scheduler.run() and the smart-plug snapshot
loop wake on their 30 s cadence and lazily reopen pool connections
holding RowExclusiveLock on print_queue / smart_plug_energy_snapshots.
The restore's DROP TABLE ... CASCADE pass needs AccessExclusiveLock on
every public table, producing an AB/BA deadlock that rolls back the
entire restore transaction.
Reproduced 2026-06-09 restoring a native install's backup into a fresh
Docker+Postgres deploy:
asyncpg.exceptions.DeadlockDetectedError: deadlock detected
Process X waits for AccessExclusiveLock on relation 109940
Process Y waits for RowExclusiveLock on relation 110182
Fix:
- Layer 1: pause print_scheduler / smart_plug_manager /
notification_service / background_dispatch via their existing stop
affordances before close_all_connections(), with a 1.0 s sleep for
in-flight loop iterations to release sessions. Restore handler
already requires a container restart on success, so the paused
services come back via the next lifespan startup.
- Layer 2: prepend SET LOCAL lock_timeout = '10s' to the begin-block
in _import_sqlite_to_postgres so any reactive writer (per-printer
MQTT, hourly AMS history recorder) that slips through the pause
window fails fast and visibly instead of producing a new deadlock.
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