True async suppport

[leo-vasiliev]

AuditProcessManager and possibly other classes are lacking true async support. Database IO operations are blocking thread pool threads because AuditProcessManager's async methods just call the sync ones.

In this example, as entities are persisted and flushed by NHibernate with ISession.FlushAsync(), Envers calls ISession.Flush() on the audit entities:

...
00007F084F1005D0 00007F09A6EBCBA7 NHibernate.Impl.SessionImpl.Flush()
00007F084F100630 00007F09A6EAADF9 NHibernate.Envers.Synchronization.AuditProcessManager+transactionCompletionProcess.ExecuteBeforeTransactionCompletion()
00007F084F100650 00007F09A6EAACFD NHibernate.Envers.Synchronization.AuditProcessManager+transactionCompletionProcess.ExecuteBeforeTransactionCompletionAsync(System.Threading.CancellationToken)
00007F084F100660 00007F09A6EA9B52 NHibernate.Engine.ActionQueue+BeforeTransactionCompletionProcessQueue+<BeforeTransactionCompletionAsync>d__0.MoveNext()
00007F084F1006E0 00007F09A6EA9207 System.Runtime.CompilerServices.AsyncMethodBuilderCore.Start[[NHibernate.Engine.ActionQueue+BeforeTransactionCompletionProcessQueue+<BeforeTransactionCompletionAsync>d__0, NHibernate]](<BeforeTransactionCompletionAsync>d__0 ByRef) [/_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncMethodBuilderCore.cs @ 38]
00007F084F100720 00007F09A6EA9172 NHibernate.Engine.ActionQueue+BeforeTransactionCompletionProcessQueue.BeforeTransactionCompletionAsync(System.Threading.CancellationToken)
00007F084F100770 00007F09A6DFE4EC NHibernate.Impl.SessionImpl+<BeforeTransactionCompletionAsync>d__79.MoveNext()
00007F084F100830 00007F099FEC10AB System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object) [/_/src/libraries/System.Private.CoreLib/src/System/Threading/ExecutionContext.cs @ 183]
00007F084F100890 00007F09A6EA8F89 System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1+AsyncStateMachineBox`1[[System.Threading.Tasks.VoidTaskResult, System.Private.CoreLib],[NHibernate.Impl.SessionImpl+<BeforeTransactionCompletionAsync>d__79, NHibernate]].MoveNext(System.Threading.Thread) [/_/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncTaskMethodBuilderT.cs @ 324]
00007F084F1008E0 00007F099FF9F396 System.Threading.Tasks.AwaitTaskContinuation.RunOrScheduleAction(System.Runtime.CompilerServices.IAsyncStateMachineBox, Boolean) [/_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/TaskContinuation.cs @ 795]
00007F084F100920 00007F099FEE19B8 System.Threading.Tasks.Task.RunContinuations(System.Object) [/_/src/libraries/System.Private.CoreLib/src/System/Threading/Tasks/Task.cs @ 3374]
00007F084F1009D0 00007F09A6DFFC31 NHibernate.Impl.SessionImpl+<FlushAsync>d__65.MoveNext()
...

[RogerKratz]

Yes, true.
I won't have time to look into this in the near future, but feel free to contribute

[leo-vasiliev]

Okay, let me see what the level of effort is, and I might give it a shot

[dennis-gr]

Fixed with #50