NServiceBus saga not working

Question

I have a handler that looks like this:

public class CreateNewUserHandler :
    Saga<UncorroboratedCreateNewUser>,
    IAmStartedByMessages<CreateNewUser>,
    IHandleMessages<FoundUser>
{

    [Dependency]
    public IBus Bus { get; set; }


    public override void ConfigureHowToFindSaga()
    {        
        ConfigureMapping<CreateNewUser>(saga => saga.CorrelationId, req => req.CorrelationId);
        ConfigureMapping<FoundUser>(saga => saga.CorrelationId, foundUser => foundUser.CorrelationId); //CorrelationId is of type Guid here
    }

    public void Handle(CreateNewUser message)
    {
        Mapper.DynamicMap(message, Data, typeof(CreateNewUser), typeof(UncorroboratedCreateNewUser));
        Data.CorrelationId = message.CorrelationId;
        Bus.Send(new FindUserByUserName { CorrelationId = Data.CorrelationId, UserName = message.UserName });
    }


    public void Handle(FoundUser message)
    {
        //**THIS BLOCK WAS NEVER HIT**
    }
}

Now the other handler that is supposed to reply with FoundUser is like this:

public class FindUserByUserNameHandler : IMessageHandler<FindUserByUserName>
{
    private readonly UserRepository _userRepository;
    public IBus Bus { get; set; }

    public FindUserByUserNameHandler(UserRepository  userRepository)
    {
        _userRepository = userRepository;
    }

    public void Handle(FindUserByUserName message)
    {
        var foundUser  = _userRepository.FindByUserName(message.UserName);
        FoundUser result = Bus.CreateInstance<FoundUser>( _ => _.CorrelationId = message.CorrelationId);
        if (foundUser != null)
        {
            result = Mapper.DynamicMap<FoundUser>(foundUser);
            result.IsUserFound = true;
        }
        else
        {
            result.
                AuthenticationUserName = message.UserName;
            result.IsUserFound = false;
        }

        Bus.Reply(result);
    }
}

In Debugging, I have been able to trace message getting into CreateNewUser => FindUserByName => Reply, and eyeballing the trace logging it even looks like the message made it back to the originating queue.

However the method void Handle(FoundUser message) was never called! I have lost a night sleep wrecking my brain and combing the internet for clues as to where I might have dropped the ball. One other thing if CreateNewUserHandler, was to be turned into a regular handler (non-saga), the method above gets called!

These are the only clues I have to go on (and it's not much - I really wished the error made more sense)

2013-05-17 14:30:29,682 [Worker.18] WARN MyProject.Unicast.Transport.Transactional.TransactionalTransport [(null)] <(null)> - Failed raising 'transport message received' event for message with ID=377f1e49-06e2-465f-877a-9443828e8866 System.NullReferenceException: Object reference not set to an instance of an object. at NServiceBus.Unicast.UnicastBus.HandleTransportMessage(IBuilder childBuilder, TransportMessage msg) in c:\TeamCity\buildAgent\work\nsb.master_7\src\unicast\NServiceBus.Unicast\UnicastBus.cs:line 1331 at NServiceBus.Unicast.UnicastBus.TransportMessageReceived(Object sender, TransportMessageReceivedEventArgs e) in c:\TeamCity\buildAgent\work\nsb.master_7\src\unicast\NServiceBus.Unicast\UnicastBus.cs:line 1248 at System.EventHandler`1.Invoke(Object sender, TEventArgs e) at NServiceBus.Unicast.Transport.Transactional.TransactionalTransport.OnTransportMessageReceived(TransportMessage msg) in c:\TeamCity\buildAgent\work\nsb.master_7\src\impl\unicast\transport\NServiceBus.Unicast.Transport.Transactional\TransactionalTransport.cs:line 480

And also

2013-05-17 14:30:29,591 [Worker.18] INFO NServiceBus.Sagas.Impl.SagaDispatcherFactory [(null)] <(null)> - Could not find a saga for the message type MyProject.Messages.FoundUser with id 377f1e49-06e2-465f-877a-9443828e8866. Going to invoke SagaNotFoundHandlers.

And just in case it's needed the configuration is:

NServiceBus.Configure.With(busAssemblies)
                        .Log4Net()
                        .License(Config.Default.NServiceBus_License)
                        .DefineEndpointName(endPointName) 
                        .UnityBuilder(serviceBusDiConfiguration.Container)
                        .DontUseTransactions() //I don't know why this is needed, but doesn't seem to get very far otherwise.
                        .AzureConfigurationSource()
                        .AzureSagaPersister()
                        .AzureSubcriptionStorage()
                        .AzureDataBus()
                        .JsonSerializer()
                        .AzureServiceBusMessageQueue()
                        .UnicastBus()
                        .LoadMessageHandlers()
                        .CreateBus()
                        .Start();
   BusConfiguration.Configurer.ConfigureComponent(uoWImplementer, DependencyLifecycle.InstancePerUnitOfWork); //For the custom unitOfWork

Please help!

=====================Message DTOs Below==========================

public class CreateNewUser : ICommand
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string UserName { get; set; }
    public string Password { get; set; }
    public Guid CorrelationId { get; set; }
}

public class FindUserByUserName : IMessage
{
    public Guid CorrelationId { get; set; }
    public string UserName { get; set; }
}

public class FoundUser: IMessage
{
    public bool IsUserFound { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string AuthenticationUserName { get; set; }
    public Guid CorrelationId { get; set; }
}

And the saga class iself:

public class UncorroboratedCreateNewUser : IContainSagaData
{
    public virtual Guid Id { get; set; }
    public virtual string Originator { get; set; }
    public virtual string OriginalMessageId { get; set; }
    public virtual string FirstName { get; set; }
    public virtual string LastName { get; set; }
    public virtual string UserName { get; set; }
    public virtual string Password { get; set; }
    public virtual Guid CorrelationId { get; set; }
}

Udi Dahan Udi Dahan · Accepted Answer · 2013-05-18T06:02:58

There are a couple of things which jump out at me.

First, try calling .Sagas() in your initialization code after Configure.With() and before .CreateBus().

Also, remove the Bus dependency on the saga - NServiceBus has that already defined on the saga class.

Remove the ConfigureMapping call for CreateNewUser (unless you expect to receive multiple instances of this message per saga).

Finally, put a [Unique] attribute on the CorrelationID property of your saga data (to guarantee that if messages are processed in parallel that you don't end up with more than one saga).

NServiceBus saga not working

2 Answers