SignalR OnDisconnected event not persisting data to DB - nhibernate

Question

I have a SignalR hub in which I'm injecting service classes which persist data to a local SQL Server instance via Castle Windsor.
The hub looks like:
[Authorize]
public class MyHub : Hub
{
private readonly IHubService _hubService;
private readonly IHubUserService _hubUserService;
private readonly IUserService _userService;
public MyHub(IHubService hubService, IHubUserService hubUserService, IUserService userService)
{
_hubService = hubService;
_hubUserService = hubUserService;
_userService = userService;
}
public async Task JoinHub(Guid hubId)
{
var hub = _hubService.GetHubById(hubId);
if (hub == null)
throw new NotFoundException(String.Format("Hub ({0}) was not found.", hubId.ToString()));
var userName = Context.User.Identity.Name;
var user = _userService.GetUserByUserName(userName);
if (user == null)
throw new NotFoundException(String.Format("User ({0}) was not found.", userName));
var hubUser = new HubUser
{
User = user,
Hub = hub,
ConnectionId = Context.ConnectionId
};
// Persist a new HubUser to the DB
hubUser = _hubUserService.InsertHubUser(hubUser);
await Groups.Add(Context.ConnectionId, hub.Id.ToString());
Clients.Group(hub.Id.ToString()).addChatMessage(userName + " has joined.");
}
public async Task LeaveHub()
{
var userName = Context.User.Identity.Name;
var hubUser = _hubUserService.GetHubUserByUserName(userName);
// Removes HubUser from the DB
_hubUserService.RemoveHubUser(hubUser);
await Groups.Remove(Context.ConnectionId, hubUser.Hub.Id.ToString());
Clients.Group(hubUser.Hub.Id.ToString()).addChatMessage(userName + " has left.");
}
public override Task OnDisconnected(bool stopCalled)
{
var userName = Context.User.Identity.Name;
var hubUser = _hubUserService.GetHubUserByUserName(userName);
// Removes HubUser from the DB
_hubUserService.RemoveHubUser(hubUser); // This line executes but does not persist anything to DB
Groups.Remove(Context.ConnectionId, hubUser.Hub.Id.ToString());
Clients.Group(hubUser.Hub.Id.ToString()).addChatMessage(userName + " has left.");
return base.OnDisconnected(stopCalled);
}
}
When calling JoinHub and LeaveHub methods from the client, everything works fine. However, when the OnDisconnected method fires, nothing is deleted from the database. I can see that the code does indeed execute, but the record remains in the DB and does not get deleted.
I'm wondering if perhaps my nhibernate session is not committing the transaction to the database due to castle windsor's dependency lifetimes or something, however, it's odd that LeaveHub executes as expected but the same code does not in the OnDisconnected method.
My dependencies are registered with the following configuration as per this blog post.
Kernel.Register(
//Nhibernate session factory
Component.For<ISessionFactory>().UsingFactoryMethod(CreateNhSessionFactory).LifeStyle.Singleton,
//Nhibernate session
Component.For<ISession>().UsingFactoryMethod(kernel => kernel.Resolve<ISessionFactory>().OpenSession()).LifeStyle.HybridPerWebRequestTransient()
);
and I also register an interceptor to implement a unit of work pattern:
// Unitofwork interceptor
Component.For<NhUnitOfWorkInterceptor>().LifeStyle.HybridPerWebRequestTransient()
If anyone can give any input on why the method LeaveHub works correctly and why it fails to persist anything in the OnDisconnected method, that'd be greatly appreciated.

Answer 1

Just an FYI Nhibernate Sessions don't do so well using async as they are not threadsafe at all. Try running things synchronously and see what you get.
Is Nhibernate set to flush on transaction commit? I can't comment becasue I am a newbie but I ran into this issue some time ago. I am not using FluentNhibernate but I am sure there is a config option to set flush on transaction commit. This is assuming you are wrapping all open session calls in a transaction. I use something like this for sessions. Also go get Nhibernate Profiler it is a godsend.
public class SessionManager : ISessionManager
{
private readonly ISessionFactory _sessionFactory;
private ISession _currentSession;
private ITransaction _currentTransaction;
public SessionManager(ISessionFactory sessionFactory)
{
_sessionFactory = sessionFactory;
}
public ISession OpenSession()
{
if (CurrentSessionContext.HasBind(_sessionFactory))
{
_currentSession = _sessionFactory.GetCurrentSession();
}
else
{
_currentSession = _sessionFactory.OpenSession();
CurrentSessionContext.Bind(_currentSession);
}
CurrentSessionContext.Bind(_currentSession);
_currentTransaction = _currentSession.BeginTransaction();
return _currentSession;
}
public void Dispose()
{
try
{
if (_currentTransaction != null && _currentTransaction.IsActive)
_currentTransaction.Commit();
}
catch (Exception)
{
if (_currentTransaction != null) _currentTransaction.Rollback();
throw;
}
finally
{
if (_currentSession != null)
{
if (_currentTransaction != null) _currentTransaction.Dispose();
_currentSession.Close();
}
}
}
}
Here is my configuration, I am using it on several apps. On a side not there is a reason I don't use FluentNhibernate, The mapping by code built in is awesome and flexible. Let me know I can send you some sample mappings.
public class SessionFactoryBuilder
{
public static ISessionFactory BuildSessionFactory(string connectionString)
{
var cfg = new Configuration();
cfg.DataBaseIntegration(db =>
{
db.Dialect<MsSql2012Dialect>();
db.Driver<Sql2008ClientDriver>();
db.ConnectionString = connectionString;
db.BatchSize = 1500;
db.LogSqlInConsole = false;
db.PrepareCommands = true;
db.ConnectionReleaseMode = ConnectionReleaseMode.AfterTransaction;
db.IsolationLevel = IsolationLevel.ReadCommitted;
})
.SetProperty(Environment.CurrentSessionContextClass, "web")
.SetProperty(Environment.UseSecondLevelCache, "true")
.SetProperty(Environment.ShowSql, "true")
.SetProperty(Environment.PrepareSql, "true")
.Cache(c =>
{
c.UseQueryCache = true;
c.Provider<RtMemoryCacheProvider>();
c.DefaultExpiration = 1440;
}).SessionFactory().GenerateStatistics();
HbmMapping mapping = GetMappings();
cfg.AddDeserializedMapping(mapping, "AppName");
SchemaMetadataUpdater.QuoteTableAndColumns(cfg);
return cfg.BuildSessionFactory();
}
private static HbmMapping GetMappings()
{
var mapper = new ModelMapper();
mapper.AddMappings(typeof (UserMap).Assembly.GetTypes());
HbmMapping mapping = mapper.CompileMappingForAllExplicitlyAddedEntities();
return mapping;
}
}
Here is a neat little bit for managing SignalR dependencies with Castle. You may want to give this a try just for giggles.
public class SignalRDependencyResolver : Microsoft.AspNet.SignalR.DefaultDependencyResolver
{
private readonly IWindsorContainer _container;
public SignalRDependencyResolver(IWindsorContainer container)
{
if (container == null)
{
throw new ArgumentNullException("container");
}
_container = container;
}
public override object GetService(Type serviceType)
{
return TryGet(serviceType) ?? base.GetService(serviceType);
}
public override IEnumerable<object> GetServices(Type serviceType)
{
return TryGetAll(serviceType).Concat(base.GetServices(serviceType));
}
[DebuggerStepThrough]
private object TryGet(Type serviceType)
{
try
{
return _container.Resolve(serviceType);
}
catch (Exception)
{
return null;
}
}
private IEnumerable<object> TryGetAll(Type serviceType)
{
try
{
Array array = _container.ResolveAll(serviceType);
return array.Cast<object>().ToList();
}
catch (Exception)
{
return null;
}
}
}
Put this in global asax before you set your controller factory
// SignalR
_container.Register(Classes.FromThisAssembly().BasedOn(typeof(IHub)).LifestyleTransient());
SignalRDependencyResolver signalRDependencyResolver = new SignalRDependencyResolver(_container);
Microsoft.AspNet.SignalR.GlobalHost.DependencyResolver = signalRDependencyResolver;