NHibernate ArgumentOutOfRangeException - session

Question

I recently ran into an instance where I wanted to hit the database from a Task I have running periodically within a web application. I refactored the code to use the ThreadStaticSessionContext so that I could get a session without an HttpContext. This works fine for reads, but when I try to flush an update from the Task, I get the "Index was out of range. Must be non-negative and less than the size of the collection." error. Normally what I see for this error has to do with using a column name twice in the mapping, but that doesn't seem to be the issue here, as I'm able to update that table if the session is associated with a request (and I looked and I'm not seeing any duplicates). It's only when the Task tries to flush that I get the exception.
Does anyone know why it would work fine from a request, but not from a call from a Task?
Could it be because the Task is asynchronous?
Call Stack:
at System.ThrowHelper.ThrowArgumentOutOfRangeException()
at System.Collections.Generic.List`1.System.Collections.IList.get_Item(Int32 index)
at NHibernate.Engine.ActionQueue.ExecuteActions(IList list)
at NHibernate.Engine.ActionQueue.ExecuteActions()
at NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions(IEventSource session)
at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event)
at NHibernate.Impl.SessionImpl.Flush()
Session Generation:
internal static ISession CurrentSession {
get {
if(HasSession) return Initializer.SessionFactory.GetCurrentSession();
ISession session = Initializer.SessionFactory.OpenSession();
session.BeginTransaction();
CurrentSessionContext.Bind(session);
return session;
}
}
private static bool HasSession {
get { return CurrentSessionContext.HasBind(Initializer.SessionFactory); }
}
Task that I want to access the database from:
_maid = Task.Factory.StartNew(async () => {
while(true) {
if(CleaningSession != null) CleaningSession(Instance, new CleaningSessionEventArgs { Session = UnitOfWorkProvider.CurrentSession });
UnitOfWorkProvider.TransactionManager.Commit();
await Task.Delay(AppSettings.TempPollingInterval, _paycheck.Token);
}
//I know this function never returns, I'm using the cancellation token for that
// ReSharper disable once FunctionNeverReturns
}, _paycheck.Token);
_maid.GetAwaiter().OnCompleted(() => _maid.Dispose());
Edit: Quick clarification about some of the types above. CleaningSession is an event that is fired to run the various things that need to be done, and _paycheck is the CancellationTokenSource for the Task.
Edit 2: Oh yeah, and this is using NHibernate version 4.0.0.4000
Edit 3: I have since attempted this using a Timer, with the same results.
Edit 4: From what I can see of the source, it's doing a foreach loop on an IList. Questions pertaining to an IndexOutOfRangeException in a foreach loop tend to suggest a concurrency issue. I still don't see how that would be an issue, unless I misunderstand the purpose of ThreadStaticSessionContext.
Edit 5: I thought it might be because of requests bouncing around between threads, so I tried creating a new SessionContext that combines the logic of the WebSessionContext and ThreadStaticSessionContext. Still getting the issue, though...
Edit 6: It seems this has something to do with a listener I have set up to update some audit fields on entities just before they're saved. If I don't run it, the commit occurs properly. Would it be better to do this through an event than OnPreInsert, or use an interceptor instead?

Answer 1

After muddling through, I found out exactly where the problem was. Basically, there was a query that was run to load the current user record called from inside of the PreUpdate event in my listener.
I came across two solutions to this. I could cache the user in memory, avoiding the query, but having possibly stale data (not that anything other than the id matters here). Alternatively, I could open a temporary stateless session and use that to look up the user in question.