DbUpdateConcurrencyException when players disconnect (no apparent data loss)

[Hyrius]

I'm getting a lot of these exceptions whenever a player disconnects.
It seems to happen quite often during player disconnects, although not consistently every time.

Environment:

• Latest master
• PostgreSQL
• Fresh installation
• No custom code changes related to persistence

Steps to reproduce:

1. Start the server.
2. Log in with a character.
3. Disconnect or exit the game.
4. The exception is logged.

No apparent data seems to be lost.
The character progress appears to be saved correctly, so I'm wondering if this is expected or if it's a bug.

One thing that caught my attention is that the log prints:
Player: "Account: [Aron], Character:[]"
The character name is empty, which also seems unusual.

Stack trace:

2026-08-05 23:57:14.889 -03:00 [Warning] [MUnique.OpenMU.Persistence.EntityFramework.PlayerContext] Transient concurrency conflict while saving (attempt 1/3); retrying.Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. See https://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.ThrowAggregateUpdateConcurrencyExceptionAsync(RelationalDataReader reader, Int32 commandIndex, Int32 expectedRowsAffected, Int32 rowsAffected, CancellationToken cancellationToken)at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.Consume(RelationalDataReader reader, Boolean async, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList1 entries, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func4 operation, Func4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesCoreAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 137
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 85

2026-08-05 23:57:14.923 -03:00 [Warning] [MUnique.OpenMU.Persistence.EntityFramework.PlayerContext] Transient concurrency conflict while saving (attempt 2/3); retrying.
Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. See https://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.ThrowAggregateUpdateConcurrencyExceptionAsync(RelationalDataReader reader, Int32 commandIndex, Int32 expectedRowsAffected, Int32 rowsAffected, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.Consume(RelationalDataReader reader, Boolean async, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList1 entries, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList1 entriesToSave, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func4 operation, Func4 verifySucceeded, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesCoreAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs 137at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs 85

2026-08-05 23:57:14.969 -03:00 [Error] [MUnique.OpenMU.GameLogic.Player] Couldn't save when leaving the game. Player: "Account: [Aron], Character:[]"Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. See https://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.ThrowAggregateUpdateConcurrencyExceptionAsync(RelationalDataReader reader, Int32 commandIndex, Int32 expectedRowsAffected, Int32 rowsAffected, CancellationToken cancellationToken)at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.Consume(RelationalDataReader reader, Boolean async, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList1 entries, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func4 operation, Func4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesCoreAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 137
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 85
   at MUnique.OpenMU.GameLogic.Player.RunPersistenceExclusiveAsync[T](Func1 operation, CancellationToken cancellationToken) in src\GameLogic\Player.cs 1905 at MUnique.OpenMU.GameLogic.Player.SaveProgressAsync(CancellationToken cancellationToken) in src\GameLogic\Player.cs 1870 at MUnique.OpenMU.GameLogic.Player.RemoveFromGameAsync() in src\GameLogic\Player.cs 1850

2026-08-05 23:57:14.992 -03:00 [Warning] [MUnique.OpenMU.Persistence.EntityFramework.PlayerContext] Transient concurrency conflict while saving (attempt 1/3); retrying.Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. See https://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.ThrowAggregateUpdateConcurrencyExceptionAsync(RelationalDataReader reader, Int32 commandIndex, Int32 expectedRowsAffected, Int32 rowsAffected, CancellationToken cancellationToken)at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.Consume(RelationalDataReader reader, Boolean async, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList1 entries, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func4 operation, Func4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesCoreAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 137
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 85

2026-08-05 23:57:15.032 -03:00 [Warning] [MUnique.OpenMU.Persistence.EntityFramework.PlayerContext] Transient concurrency conflict while saving (attempt 2/3); retrying.
Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. See https://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.ThrowAggregateUpdateConcurrencyExceptionAsync(RelationalDataReader reader, Int32 commandIndex, Int32 expectedRowsAffected, Int32 rowsAffected, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.Consume(RelationalDataReader reader, Boolean async, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList1 entries, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList1 entriesToSave, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func4 operation, Func4 verifySucceeded, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesCoreAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs 137 at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs 85 

2026-08-05 23:57:15.079 -03:00 [Error] [MUnique.OpenMU.GameLogic.Player] Couldn't save when leaving the game. Player: "Account: [Aron], Character:[]"Microsoft.EntityFrameworkCore.DbUpdateConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. See https://go.microsoft.com/fwlink/?LinkId=527962 for information on understanding and handling optimistic concurrency exceptions.at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.ThrowAggregateUpdateConcurrencyExceptionAsync(RelationalDataReader reader, Int32 commandIndex, Int32 expectedRowsAffected, Int32 rowsAffected, CancellationToken cancellationToken)at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlModificationCommandBatch.Consume(RelationalDataReader reader, Boolean async, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.ExecuteAsync(IRelationalConnection connection, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken) at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList1 entries, CancellationToken cancellationToken)at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func4 operation, Func4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesCoreAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 137
   at MUnique.OpenMU.Persistence.EntityFramework.EntityFrameworkContextBase.SaveChangesAsync(CancellationToken cancellationToken) in src\Persistence\EntityFramework\EntityFrameworkContextBase.cs:line 85
   at MUnique.OpenMU.GameLogic.Player.RunPersistenceExclusiveAsync[T](Func1 operation, CancellationToken cancellationToken) in src\GameLogic\Player.cs 1905 at MUnique.OpenMU.GameLogic.Player.SaveProgressAsync(CancellationToken cancellationToken) in src\GameLogic\Player.cs 1870 at MUnique.OpenMU.GameLogic.Player.RemoveFromGameAsync() in src\GameLogic\Player.cs 1850

[cleberto]

Root Cause

Race condition between PeriodicSaveProgressPlugIn and RemoveFromGameAsync() disconnect flow.

The PlayerPersistence lock ( _lock ) was designed to serialize packet-handler entity mutations against periodic saves. However, RemoveFromGameAsync() was modifying tracked EF entities ( SetSelectedCharacterAsync(null) , ClearAllEffectsAsync() , setting OpenedNpc = null ) outside this lock, then calling SaveProgressAsync() at the end.

The PeriodicSaveProgressPlugIn runs on an independent timer and calls player.SaveProgressAsync() for all players in EnteredWorld state. When it fires concurrently with a disconnect:

1. The periodic save acquires the lock and calls Context.SaveChangesAsync(acceptChanges: true) on the player's shared DbContext
2. During the async DB round-trip, RemoveFromGameAsync() modifies the same tracked entities on the same DbContext
3. The periodic save's AcceptAllChanges() accepts un-persisted state, or the change tracker ends up with stale xmin tokens (PostgreSQL's row version)
4. The disconnect's subsequent SaveProgressAsync() hits DbUpdateConcurrencyException because the xmin WHERE clause matches 0 rows

The two error blocks in the log correspond to RemoveFromGameAsync() being called twice during LogoutType.CloseGame — once from LogoutAction.LogoutAsync() and once from DisconnectAsync() → InternalDisconnectAsync() .

The empty Character:[] is expected — SetSelectedCharacterAsync(null) sets _selectedCharacter = null before SaveProgressAsync() is called.

Fix

Wrapped the entity mutations and the final save inside RunPersistenceExclusiveAsync() , which serializes them under the same PlayerPersistence._lock that the periodic save uses. The inner SaveProgressAsync() → RunExclusiveAsync() call is safely re-entrant via the AsyncLocal _lockHeld flag, so it runs the save without re-acquiring the lock.