Could not synchronize database state with session- Nhibernate and Rebus concurrency issue - nhibernate

Question

When using Rebus with Nhibernate, while storing the subscriber details in table getting error like
NHibernate.Event.Default.AbstractFlushingEventListener
NHibernate.AdoNet.TooManyRowsAffectedException: Unexpected row count: 5; expected: 1
at NHibernate.AdoNet.Expectations.BasicExpectation.VerifyOutcomeNonBatched(Int32 rowCount, IDbCommand statement)
at NHibernate.Persister.Entity.AbstractEntityPersister.Update(Object id, Object[] fields, Object[] oldFields, Object rowId, Boolean[] includeProperty, Int32 j, Object oldVersion, Object obj, SqlCommandInfo sql, ISessionImplementor session)
at NHibernate.Persister.Entity.AbstractEntityPersister.UpdateOrInsert(Object id, Object[] fields, Object[] oldFields, Object rowId, Boolean[] includeProperty, Int32 j, Object oldVersion, Object obj, SqlCommandInfo sql, ISessionImplementor session)
at NHibernate.Persister.Entity.AbstractEntityPersister.Update(Object id, Object[] fields, Int32[] dirtyFields, Boolean hasDirtyCollection, Object[] oldFields, Object oldVersion, Object obj, Object rowId, ISessionImplementor session)
at NHibernate.Action.EntityUpdateAction.Execute()
at NHibernate.Engine.ActionQueue.Execute(IExecutable executable)
at NHibernate.Engine.ActionQueue.ExecuteActions(IList list)
at NHibernate.Engine.ActionQueue.ExecuteActions()
at NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions(IEventSource session)
This may happen due to all subscriber concurrency, because If I use debugger, then it work unexpectedly as enough time passes.
Getting exception in this code
public void Insert(ISagaData sagaData, string[] sagaDataPropertyPathsToIndex)
{
try
{
var nSagaData = new NDbSagaData
{
Id = sagaData.Id,
Revision = sagaData.Revision++,
Data = JsonConvert.SerializeObject(sagaData, Formatting.Indented, Settings)
};
PersistenceManager.Save(nSagaData);
}
catch (Exception ex)
{
_log.Error("Insert Exception " + ex.Message);
System.IO.File.AppendAllText("C:\\TestFolder\\WriteText.txt", "Insert fromSource - " + ex.Message);
throw new OptimisticLockingException(sagaData, ex);
}
}
and it says, 'Unexpected row count: 3; expected: 1'
What will be the reason?

Answer 1

It looks like you have implemented a saga persister based on NHibernate, and it seems like it has detected a race condition, which I am guessing results in a rolled-back transaction.
I guess the question is why a race condition occurred. The "unexpected row count" exception occurs when NHibernate's optimistic concurrency check fails, but in that case I would have expected a message saying "unexpected row count 0; expected 1".
If I were you, I would use Rebus' built-in SQL Server saga persister, as it seems you are serializing the saga data into a single column anyway.