I'm working on an application that requires regular polling of a 3rd party API. We've used NServiceBus heavily throughout this project and I decided to use the benefits of a Saga to help maintain the state of my poller.
In short, the Saga is used to maintain information required to ensure the polling is done correctly, and also to give us the simplicity of creating a timeout (after each poll) in order to ensure the next poll takes place, even if the service is stopped/compromised/blocked for whatever reason.
My first issue arose when I decided to initiate the Saga by having the service subscribe to its own events, and then publish one of those events when the service started (using IWantToRunWhenBusStartsAndStops). The problem with that was that the service would start and therefore publish the event, but it would happen before the subscriptions were created. The service would therefore not handle the event that was meant to kick off the whole Saga, unless I restarted it. Restarting the service in order to bypass this problem is not a solution that I want to even consider.
Since then, and with some playing around, I have discovered that using
Bus.SendLocal(new MyMessage()); (MyMessage implements IMessage)
will effectively start the Saga, without the need for subscription. The Saga is created in the database (I use NHibernate & MSSQL for persistence), and the timeouts are correctly created and function exactly as expected.
My only problem with this solution is that I am doing something that I cannot find any reference to in the NServiceBus documentation, and I'm concerned that I may be utilising a "feature" that may disappear in a future version, due to actually being an unintended side-effect.
In a nutshell - I'm starting a Saga by sending an IMessage using SendLocal. It works 100% and fixes all my issues, but is it "correct"?
Your solution is absolutely correct and there is no reason I can think of not to do that.